11 3,4,5 - Chemistry Mock Exam Revision - Foundation
C2.4 Rates of reaction Revision Foundation
Q1.
Pieces of zinc react with dilute acid to form hydrogen gas.
The graph shows how the volume of hydrogen gas produced changes with time.
(a)
Describe, as fully as you can, how the volume of gas produced changes with time.
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
A student wants to make the reaction take place faster.
Some suggestions are given in the table.
Put ticks ( ) next to the two suggestions that would make the reaction take place faster.
Suggestions
( )
Use bigger pieces of zinc.
Use a more concentrated acid.
Use zinc powder.
Decrease the temperature of the acid.
(2)
(Total 4 marks)
Q2.
(a)
Hydrogen peroxide (H2O2) contains the same elements as water (H2O).
Name the hazard symbol shown by using the correct word from the box.
corrosive
flammable
oxidising
toxic
(1)
(b)
Hydrogen peroxide decomposes in the presence of a catalyst.
2H2O2(aq) → 2H2O(l) + O2(g)
(i)
Complete the word equation for this chemical reaction.
hydrogen peroxide → water + ................................
(1)
(ii)
What does a catalyst do to a chemical reaction?
...........................................................................................................................
...........................................................................................................................
(1)
(Total 3 marks)
Q3.
A student investigated the rate of reaction between marble and hydrochloric acid.
The student used an excess of marble.
The reaction can be represented by this equation:
CaCO3(s)
+
2HCl(aq)
→
CaCl2(aq)
The student used the apparatus shown in the diagram.
+
H2O(l)
+
CO2(g)
The student measured the mass of the flask and contents for ten minutes.
The results are shown on the graph. Use the graph to answer the questions.
(a)
(i)
Complete the graph by drawing a line of best fit.
(1)
(ii)
Use the graph to find the mass of the flask and contents after 1.8 minutes.
................................. grams
(1)
(iii)
The rate of reaction can be measured by the steepness of the graph line.
Describe, as fully as you can, how the rate of reaction changes with time in this experiment.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(b)
The mass of the flask and contents decreased during the experiment.
Use the equation for this reaction to help you explain why.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)
(c)
A balance is used to measure the mass of the apparatus.
(i)
Which balance, A, B, or C, has the highest resolution (most precise)?
Balance A
Balance B
Balance C
The balance with the highest resolution is balance
(1)
(ii)
The balance used for this experiment should have a high resolution.
Explain why.
...............................................................................................................
...............................................................................................................
(2)
(d)
The student repeated the experiment using powdered marble instead of marble chips.
The rate of reaction between the marble and hydrochloric acid particles was much faster with the
powder.
Explain why.
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)
(Total 11 marks)
Q4.
A student studied the effect of temperature on the rate of reaction between hydrochloric acid and
sodium thiosulphate.
•
The student mixed 50 cm3 of a sodium thiosulphate solution and 5 cm3 of hydrochloric acid in a
flask.
•
The flask was placed over a cross.
•
The student timed how long after mixing the cross could no longer be seen.
(a)
(i)
Balance the chemical equation for this reaction.
Na2S2O3(aq) + HCl(aq) → NaCl(aq) + H2O(l) + SO2(g) + S(s)
(1)
(ii)
What causes the cross to be seen no longer?
..........................................................................................................................
(1)
(b)
A graph of the results is shown.
(i)
What effect does temperature have on the rate of this reaction?
..........................................................................................................................
(1)
(ii)
Explain why temperature has this effect on the rate of reaction.
..........................................................................................................................
..........................................................................................................................
(2)
(Total 5 marks)
Q5.
Sodium thiosulfate solution reacts with hydrochloric acid. As the reaction takes place the solution
slowly turns cloudy.
The diagram shows a method of measuring the rate of this reaction.
A student used this method to investigate how changing the concentration of the sodium thiosulfate
solution affects the rate of this reaction. The student used different concentrations of sodium
thiosulfate solution. All the other variables were kept the same. The results are shown on the graph
below.
(a)
(i)
Draw a line of best fit on the graph.
(1)
(ii)
Suggest two reasons why all of the points do not lie on the line of best fit.
1 ........................................................................................................................
...........................................................................................................................
2 ........................................................................................................................
...........................................................................................................................
(2)
(b)
(i)
In a conclusion to the investigation the student stated that:
‘The rate of this reaction is directly proportional to the concentration of the sodium
thiosulfate solution.’
How does the graph support this conclusion?
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Explain, in terms of particles, why the rate of reaction increases when the concentration of
sodium thiosulfate is increased.
...........................................................................................................................
...........................................................................................................................
(2)
(Total 6 marks)
Q6.
A student investigated the rate of reaction between marble and hydrochloric acid.
The student used an excess of marble.
The reaction can be represented by this equation.
CaCO3 (s) + 2HC1 (aq) → CaC12 (aq) + H2O (l) + CO2 (g)
The student used the apparatus shown in the diagram.
The student measured the mass of the flask and contents every half minute for ten minutes.
The results are shown on the graph. Use the graph to answer the questions.
(a)
Complete the graph opposite by drawing a line of best fit.
(1)
(b)
Why did the mass of the flask and contents decrease with time?
.....................................................................................................................................
.....................................................................................................................................
(1)
(c)
After how many minutes had all the acid been used up?
.............................. minutes
(1)
(d)
The student repeated the experiment at a higher temperature. All other variables were kept the
same as in the first experiment. The rate of reaction was much faster.
(i)
Draw a line on the graph to show what the results for this second experiment might look
like.
(2)
(ii)
Why does an increase in temperature increase the rate of reaction?
...........................................................................................................................
...........................................................................................................................
(3)
(Total 8 marks)
Q7.
A student does an experiment to examine the rate of reaction between magnesium and dilute
hydrochloric acid.
She adds 25 cm³ of the acid to a weighed amount of the metal.
The reaction produces hydrogen gas.
Magnesium + hydrochloric
acid
magnesium + hydrogen
chloride
She collects the gas and measures the volume collected at one minute intervals.
All the metal reacted but there was some acid left unreacted.
Her results are shown on the graph.
(a)
The diagram shows part of the apparatus she used for the experiment.
Complete the diagram to show how the student could collect the hydrogen produced and
measure the volume after each minute.
(2)
(b)
(i)
When is the rate of reaction at its fastest?
..........................................................................................................................
(1)
(ii)
State one way in which she could increase the rate of reaction.
..........................................................................................................................
(1)
(c)
(i)
What is the total volume of hydrogen collected in the experiment?
................................................................................................................... cm³
(1)
(ii)
State one way in which she could increase the final volume of hydrogen collected.
..........................................................................................................................
(1)
Q8.
Calcium carbonate reacts with dilute hydrochloric acid as shown in the equation below.
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
The rate at which this reaction takes place can be studied by measuring the amount of carbon dioxide
gas produced. The graph below shows the results of four experiments, 1 to 4. In each experiment the
amount of calcium carbonate, the volume of acid and the concentration of the acid were kept the same
but the temperature of the acid was changed each time. The calcium carbonate was in the form of
small lumps of marble.
(a)
Apart from altering the temperature, suggest two ways in which the reaction of calcium
carbonate and hydrochloric acid could be speeded up.
1. ................................................................................................................................
2. ................................................................................................................................
(2)
(b)
Which graph, 1 to 4, shows the results of the experiment in which the acid had the highest
temperature?
Experiment ................................................
Explain fully how you know.
.....................................................................................................................................
.....................................................................................................................................
(2)
(c)
(i)
In experiment 2, how does the rate of reaction after one minute compare with the rate of
reaction after two minutes?
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Explain, as fully as you can, why the reaction rate changes during experiment 2.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(Total 7 marks)
M1.
(a)
any two from:
•
increases
owtte allow ‘goes up’
•
until reaches maximum / levels off
owtte
•
quickly at first
owtte
•
then more slowly / rate decreases
allow reaction finished
ignore rate increases
2
(b)
use a more concentrated acid
list principle applies
use zinc powder
2
[4]
M2.
(a)
oxidising
1
(b)
(i)
oxygen
ignore any numbers
1
(ii)
(catalyst) speeds up a (chemical reaction)
accept changes the rate (of reaction)
1
[3]
M3.
(a)
(i)
curve missing anomalous point
1
(ii)
answer in the range of 100.35 to 100.5
1
(iii)
reaction goes quickly at first
accept reaction slows down
1
reaction stops
1
(b)
because carbon dioxide is produced
accept gas is produced
1
carbon dioxide / gas escapes, therefore the mass of the
flask and contents decreases
1
(c)
(i)
balance B
1
(ii)
because during the experiment a gas / carbon
dioxide escapes from the flask
1
therefore the balance needs a high resolution to
measure the small changes in the mass
1
(d)
the (marble) powder has a larger surface area than the
(marble) chips
1
therefore there would be more collisions with the acid particles
(within the same amount of time)
1
[11]
M4.
(a)
(i)
Na2S2O3(aq) + 2 HCl(aq) → 2NaCl(aq) + H2O(l) + S(s) + SO2(g)
1
(ii)
(formation of) sulphur
accept precipitate or solid produced
do not accept goes cloudy or milky
1
(b)
(i)
heat ≡ temperature increased temperature increases (the rate of reaction)
or decreased temperature decreases rate of reaction
may be gained in part (ii) if stated and not implied
1
(ii)
(these ideas may be given in (i))
particles have more kinetic energy
accept particles move faster
1
more collisions (so more reactions)
more energetic collisions two marks
1
[5]
M5.
(a)
(i)
a continuous straight line missing anomalous point
allow a line which does not start at zero / origin
1
(ii)
any two sensible errors eg
•
timing errors and / or example(*)
•
measurement errors and / or example(*)
•
apparatus errors and / or example(*)
•
human / experimental / random error and / or example
or ‘did not do it right’(*)
(*)could be two from same category eg two timing errors – watch not
started at the same time plus difficulty in deciding when the cross has
disappeared.
•
temperature fluctuation
•
anomalous point
accept outlier / wrong result
•
results not recorded correctly
•
plotting error
•
rate calculated incorrectly
ignore ‘not repeated’
ignore systematic / zero error / weighing error or error unqualified
2
(b)
(i)
straight line
or
as concentration increases the rate goes up or converse
accept numerical example
accept positive correlation
accept same gradient
ignore ‘most points near / on line of best fit’
1
(ii)
more collisions
accept greater chance of collisions
accept collide more successfully
accept alternative versions of collide eg ‘bump / hit’
ignore references to energy / speed of particles / surface area
1
more particles (in each volume of solution)(i.e. an attempt at defining concentration)
accept ‘particles are closer together’
allow ions / atoms / molecules for particles ignore reactants
accept greater frequency of collisions or greater number of collisions per
second for 2 marks
1
[6]
M6.
(a) sensible line of best fit which goes through or close to all the points except
the anomalous point
1
(b)
loss of gas / loss of CO2
idea of gas produced / formed
1
(c)
7
1
(d)
(i)
steeper line from around the same starting point
and left of the points
allow crosses if they are fully correct for 1 mark
1
levelling off at 99
accept short level line at 99
± ½ square
1
(ii)
any three from:
•
particles / molecules / atoms/ ions have more energy
allow given / gain / get energy
•
move faster
ignore move about more
ignore vibrate more / faster
•
collide more often
or more chance of collisions
or bump into each other more
ignore collide quicker / faster
•
collide with more force / energy
or more particles have the activation energy
or more collisions result in reaction
or more collisions are successful
3
[8]
M7.
(a)
(must be possible for the gas to enter and displace the water) or other suitable apparatus
•
apparatus to collect the gas correctly assembled
for 1 mark
•
calibrated collection vessel (award even if diagram is wrong)
for 1 mark
2
(b)
(i)
at the start / in the first 1/2 minutes (or any time within this range)
for 1 mark
1
(ii)
increase the temperature / use smaller pieces of metal /
use more metal / increase the surface area of the metal /
add a catalyst / shake the flask / increase the concentration /
strength of the acid
for 1 mark
1
(c)
(i)
48
for 1 mark
1
(ii)
increase the amount of magnesium used
for 1 mark
(do not allow increase the amount of acid used)
1
[6]
M8.
(a) increase concentration of acid;
increase surface area of solid
or grind up the solid;
add a catalyst
any two for 1 mark each
2
(b)
1;
it is the one that makes the gas fastest (steeper curve etc)
(second part is dependant on first)
for 1 mark each
2
(c)
(i)
faster after one minute, slower after 2 minutes
for 1 mark
1
(ii)
the reactants get used up;
so concentration decreases/less chance of collision
for 1 mark each
2
[7]
C2.5 Exothermic and endothermic reactions Revision Foundation
Q1.
Distress flares are used to attract attention in an emergency.
Flares often contain magnesium. Magnesium burns to form magnesium oxide.
(a)
The distress flare burns with a bright flame because the reaction is very exothermic.
Complete the following sentence using the correct words from the box.
gives out heat
stores heat
takes in heat
An exothermic reaction is one which ..........................................................................
(1)
(b)
Indigestion tablets can be made from magnesium oxide. The magnesium oxide neutralises
some of the hydrochloric acid in the stomach.
Draw a ring around the name of the salt formed when magnesium oxide reacts with hydrochloric
acid.
magnesium chloride
magnesium hydroxide
magnesium sulfate
(1)
Q2.
An indigestion tablet contains sodium hydrogencarbonate and citric acid.
When the tablet is added to cold water a chemical reaction takes place and there is a lot of fizzing.
(a)
The formula of the gas that causes the fizzing is CO2
Name this gas ......................................................................... .
(1)
(b)
This chemical reaction is endothermic.
(i)
Tick ( ) the statement which describes what happens to the temperature of the solution.
Statement
Tick ( )
The temperature of the solution will increase.
The temperature of the solution will decrease.
The temperature of the solution will stay the same.
(1)
(ii)
Tick ( ) the statement which describes what happens to the energy during the reaction.
Statement
Tick ( )
Energy is given out to the surroundings.
Energy is taken in from the surroundings.
No energy is given out to or taken from the surroundings.
(1)
Q3.
Instant cold packs are used to treat sports injuries.
One type of cold pack has a plastic bag containing water. Inside this bag is a smaller bag containing
ammonium nitrate. The outer bag is squeezed so that the inner bag bursts. The pack is shaken and
quickly gets very cold as the ammonium nitrate dissolves in the water.
(a)
One of the statements in the table is correct.
Put a tick ( ) next to the correct statement.
Statement
( )
The bag gets cold because heat energy is given out to the surroundings.
The bag gets cold because heat energy is taken in from the surroundings.
The bag gets cold because plastic is a good insulator.
(1)
(b)
Draw a ring around the word that best describes the change when ammonium nitrate dissolves
in water.
electrolysis
endothermic
exothermic
(1)
(c)
Suggest and explain why the pack is shaken after the inner bag has burst.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 4 marks)
Q4.
The diagram shows some magnesium ribbon burning.
(a)
Choose words from the list to complete the sentences below.
electrical
an endothermic
heat
an exothermic
light
a neutralisation
kinetic
a reduction
When magnesium burns, it transfers .........................................................................
and ............................................................................ energy to the surroundings.
We say that it is .................................................................................. reaction.
(3)
(b)
Complete the word equation for the reaction.
magnesium + __________________________
magnesium oxide
(1)
(Total 4 marks)
Q5.
The diagram shows the apparatus for an experiment. Hydrated copper sulphate crystals were
heated. They became anhydrous copper sulphate.
(a)
Name a suitable piece of equipment to heat tube A.
.....................................................................................................................................
(1)
(b)
Use words from the box to complete the two spaces in the table. You may use each word once
or not at all.
black
blue
orange
red
purple
white
Name
Colour
Hydrated copper sulphate crystals
...................................................
Anhydrous copper sulphate
....................................................
(2)
(c)
What is the purpose of the ice and water in the beaker?
.....................................................................................................................................
.....................................................................................................................................
(1)
(d)
Drops of a clear, colourless liquid formed on the inside of tube B.
(i)
Name the liquid.
...........................................................................................................................
(1)
(ii)
Explain how the liquid came to be inside tube B.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(e)
Anhydrous copper sulphate can be turned into hydrated copper sulphate. What would you need
to add? Apart from the change in colour, what could you observe?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(f)
Copper sulphate can be made from black copper oxide by reacting it with an acid. Name the
acid.
.....................................................................................................................................
(1)
(Total 10 marks)
Q6.
A student did two experiments using ammonium chloride.
(a)
In the first experiment the student heated a small amount of ammonium chloride in a test tube.
Two reactions take place in the test tube.
Reaction 1
Reaction 2
(i)
ammonium chloride → ammonia + hydrogen chloride
(colourless gases)
ammonia + hydrogen chloride → ammonium chloride
Complete the sentences by crossing out the incorrect word in each box.
Reaction 1 takes place at a
high
low
temperature.
Reaction 2 takes place at a
high
low
temperature.
(1)
(ii)
Draw a ring around the word which best describes reactions 1 and 2.
combustion
displacement
oxidation
reduction
reversible
(1)
(iii)
Suggest a reason for the mineral wool at the top of the test tube.
...........................................................................................................................
...........................................................................................................................
(1)
(b)
In the second experiment the student mixed a small amount of ammonium chloride with some
water in a beaker.
The temperature of the water was measured before and after adding the ammonium chloride.
Temperature before
adding the ammonium
chloride
20°C
Temperature after adding
the ammonium chloride
16°C
Draw a ring around the word which best describes the process which takes place.
combustion
displacement
endothermic
exothermic
freezing
(1)
(Total 4 marks)
M1.
(a)
gives out (heat)
1
(b)
magnesium chloride
1
[2]
M2.
(a)
carbon dioxide
must be name
do not accept carbon oxide
1
(b)
(i)
the temperature of the solution will decrease
(list principle)
1
(ii)
energy is taken in from the surroundings
(list principle)
1
[3]
M3.
(a)
the bag gets cold because heat energy is taken in from the surroundings
1
(b)
endothermic
1
(c)
any two from:
•
mix / spread (the ammonium nitrate and water)
•
dissolve faster(*)
•
get cold faster or so the whole bag gets cold(*)
(*)allow increase rate or quicker reaction
•
particles collide more or more collisions
2
[4]
M4.
(a) heat
light
an exothermic
in any order for 1 mark each
3
(b)
oxygen / O2
for 1 mark
1
[4]
M5.
(a)
Bunsen (burner)
accept spirit burner do not credit candle
1
(b)
blue
1
white
credit (1) if both colours correct but answers are reversed
1
to cool the tube (B)
accept answers which anticipate part (d) e.g. ‘to condense the water
vapour’ or gases or vapours
1
(d)
(i)
water
do not credit ‘condensation’
1
(ii)
(Water) vapour from the crystals (from tube A)
accept steam or steam from tube A
1
condenses or cools
accept turns to (liquid) water
1
(e)
add water
gets hot or hotter or warm or warmer turns into solution
dissolves
or the temperature rises or there is an exothermic reaction
accept steams or hisses ignore any reference to colour(s)
2
(f)
sulphuric acid
accept H2S04 only if correct in every
detail
1
[10]
M6.
(a)
(i)
high and low
both needed for mark
1
(ii)
reversible
1
(iii)
to prevent ammonium chloride / solid / particles escaping
idea of a filter
do not accept ‘to prevent gases escaping’
1
(b)
endothermic
1
[4]
C2.6 Acids, bases and salts Revision Foundation
Q1.
(a)
(i)
The diagram shows one way of making crystals of copper sulphate.
Why was the solution filtered?
..........................................................................................................................
(1)
(ii)
How could you make the crystals form faster from the copper sulphate solution?
..........................................................................................................................
(1)
(iii)
The chemical equation is shown for this reaction.
CuO(s) + H2SO4(aq) → CuSO4(aq) + H2O(l)
In the chemical equation what does (aq) mean?
..........................................................................................................................
(1)
(b)
Blue copper sulphate crystals go white when warmed. How could you use the white copper
sulphate as a test for water?
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(Total 5 marks)
Q2.
A solution of Y was slowly added to a solution of X. The graph shows how the pH of the resulting
solution changed.
(a)
(i)
What was the pH of solution X before any of solution Y was added?
...........................................................................................................................
(1)
(ii)
State whether solution Y was acidic, alkaline or neutral.
...........................................................................................................................
(1)
(iii)
What volume of solution Y was needed to react with all of the substance in solution X?
.................................................................................................................... cm3
(1)
(b)
The chemical equation shows the reaction between an acid and an alkali to form a salt and
water.
(i)
Draw a circle round the formula of the alkali.
H2SO4
+
2KOH
→
K2SO4
+
2H2O
(1)
(ii)
What is the formula of the salt?
...........................................................................................................................
(1)
(Total 5 marks)
Q3.
Salts can be prepared by the reaction of acids with alkalis.
(a)
(i)
The reactions of acids with alkalis can be represented by the equation below. Choose a
substance from the box to complete the equation.
carbon dioxide
hydrogen
oxygen
water
acid + alkali → salt + ..........................................................
(1)
(ii)
Draw a ring around the word which best describes the reaction.
displacement
neutralisation
oxidation
reduction
(1)
(b)
Sodium sulphate is an important salt. The table gives a list of some substances.
Put a tick ( ) next to the names of the acid and the alkali that would react to make sodium
sulphate.
Substances
( )
Hydrochloric acid
Nitric acid
Potassium sulphate
Sodium hydroxide
Sodium nitrate
Sulphuric acid
(2)
Q4.
(a) Citric acid produces hydrogen ions in aqueous solution. These ions can be represented as
H+(aq). Complete this sentence.
The (aq) means that the acid has been dissolved in .................................................. .
(1)
(c)
Citric acid is a weak acid. Draw a ring around the correct answer to complete the sentence.
has a low boiling point.
The word weak means that the acid
is dilute.
is partially ionised in water.
(1)
(d)
A student measured the pH of four acids, A, B, C and D.
The acids were the same concentration. The same quantity of magnesium ribbon was added to
each of the acids. The volume of gas produced after 5 minutes was recorded.
The results are shown in the table.
(i)
Acid
pH
Volume of gas in cm3
A
2
18
B
5
6
C
1
24
D
4
12
State one way in which the student made sure that the experiment was fair.
...........................................................................................................................
(1)
(ii)
Use the results to arrange the acids, A, B, C and D in order of decreasing acid strength.
Most acidic ........................................................................................ Least acidic.
(1)
(e)
When acids react with alkalis, the hydrogen ions from the acid react with the hydroxide ions from
the alkali.
(i)
Which one of the following represents the formula of a hydroxide ion?
Draw a ring around your answer.
H–
O–
OH–
(1)
(ii)
Draw a ring around the correct answer to complete the sentence.
acidic.
A solution with more hydrogen ions than hydroxide ions is
alkaline.
neutral.
(1)
(Total 7 marks)
Q5.
Nitric acid can be neutralised by alkalis to make salts.
(i)
The salt called potassium nitrate can be made from nitric acid.
Complete the word equation for this neutralisation reaction.
Choose the correct substances from the box.
hydrogen
oxygen
potassium chloride
potassium hydroxide
water
nitric acid + ................................ →potassium nitrate + ................................
(2)
(ii)
Ammonium nitrate is another salt made from nitric acid.
Which one of the following is the main use of ammonium nitrate? Draw a ring around your
answer.
dye
fertiliser
plastic
fuel
(1)
(iii)
Complete this sentence by choosing the correct ion from the box.
H+
NH4+
NO3–
O2–
OH–
The ion that makes solutions acidic is ............................................................ .
(1)
(Total 4 marks)
Q6.
A student tried to make some magnesium sulphate. Excess magnesium was added to dilute
sulphuric acid. During this reaction fizzing was observed due to the production of a gas.
(i)
Complete and balance the chemical equation for this reaction.
..................... + H2SO4 → ....................... + ........................
(3)
(ii)
At the end of the reaction the solution remaining was filtered. Why was the solution filtered?
.....................................................................................................................................
(1)
(iii)
The filtered solution was left in a warm place.
Explain why the filtered solution was left in a warm place.
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 6 marks)
Q7.
Ammonium nitrate and ammonium sulphate are used as fertilisers.
(i)
Which acid reacts with ammonia to form ammonium nitrate?
....................................................................................................................................
(1)
(ii)
Which acid reacts with ammonia to form ammonium sulphate?
....................................................................................................................................
(1)
(iii)
The reactions in (i) and (ii) are both exothermic. How can you tell that a reaction is exothermic?
....................................................................................................................................
(1)
(iv)
The reactions in (i) and (ii) are both examples of acid + base reactions. What is the name of the
chemical change which takes place in every acid + base reaction?
....................................................................................................................................
(1)
(Total 4 marks)
Q8.
The following passage is about the preparation of lead iodide, an insoluble salt.
An excess of potassium iodide in solution was shaken with
some lead nitrate solution in a test tube.
The lead iodide precipitate was separated from the mixture
and then washed several times with water.
The lead iodide was dried and then placed in a bottle.
(a)
Suggest a reason why excess potassium iodide was used.
.....................................................................................................................................
.....................................................................................................................................
(1)
(b)
What word used in the passage shows that lead iodide is insoluble?
....................................................................................................................................
(1)
(c)
Suggest how lead iodide can be separated from the mixture.
....................................................................................................................................
....................................................................................................................................
(1)
(d)
Why was the lead iodide washed with water?
....................................................................................................................................
....................................................................................................................................
(1)
(e)
Suggest a method which could be used to dry this lead iodide.
....................................................................................................................................
....................................................................................................................................
(1)
(f)
Lead compounds are toxic.
Suggest a suitable safety precaution that should be taken when using toxic substances in
laboratories.
....................................................................................................................................
(1)
(Total 6 marks)
Q9.
The diagrams show what happens when an acid is added to an alkali.
(a)
What is present in the flask at stage 2, besides universal indicator and water?
.....................................................................................................................................
(1)
(b)
Write an ionic equation to show how water is formed in this reaction and state the sources of the
ions.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 4 marks)
M1.
(a)
(i)
to remove or separate copper oxide
accept to remove or separate
unreacted or excess base
accept to remove or separate insoluble solids
1
(ii)
heat (the solution)
accept heat the water
accept evaporate the water
rapid cooling/cool to lower temperature
accept boil the water or solution
not increase surface area, put in
draught
not increase the temperature
1
(iii)
aqueous
accept in water
accept solution
not soluble in water
1
(b)
add water/liquid/solution
1
colour changes to blue
1
[5]
M2.
(a)
(i)
allow a number between 2.5 and 3
(inclusive)
accept just under 3 or about 3
1
(ii)
alkaline or alkali
1
(iii)
25
ignore any reference to units
1
(b)
(i)
a circle round KOH or 2 KOH
1
(ii)
K2SO4
do not credit potassium sulphate
1
[5]
M3.
(a)
(i)
water
accept H2O
accept correct ringed answer in box
1
(ii)
neutralisation
accept underlining or any indication, eg tick
1
(b)
sodium hydroxide
1
sulphuric acid
apply list principletotal
1
[4]
M4.
(a)
water / H2O / hydrogen oxide
1
(b)
is partially ionised in water
1
(d)
(i)
eg same concentration / quantity of Mg
accept: volume of acid / ribbon for both / same time
accept: volume of gas measured under the same conditions
1
(ii)
CADB
1
(e)
(i)
OH–
1
(ii)
acidic
1
[7]
M5.
(i)
potassium hydroxide
accept correct formulae
1
water
1
(ii)
fertiliser
1
(iii)
H+
accept hydrogen but not H
1
[4]
M6.
Mg + (H2SO4) →
(i)
1
MgSO4 +
1
H2
deduct 1 mark if not balanced only if all three correct
accept alternative metal of similar reactivity for example Zn or Fe
candidate would not then be awarded first mark for Mg
then error carried forward
deduct 1 mark if not balanced only if all three correct
1
(ii)
to remove the (excess) magnesium
accept separate
accept insoluble substances or solids or residue
do not accept unreactive substances or impurities or remove
magnesium from sulphuric acid
1
(iii)
to evaporate (some of the water or solution)
1
to form crystals or crystallise
accept to form a saturated solution
or concentrated solution
do not accept to leave MgSO4
1
[6]
M7.
NOTE
In this question and throughout the Paper, if the name of a chemical is
asked for, then the formula is acceptable only if it is correct in every detail.
If the name is correct and the candidate has tried to be ‘helpful’ by giving,
in addition, an incorrect version of the formula, then this is acceptable
provided it does not lead to ambiguity.
(i)
nitric (acid)
accept HN03
1
(ii)
sulphuric (acid)
accept H2SO4
1
(iii)
heat given out
or temperature rise
or energy given out
or steam
do not credit just ‘use a thermometer’
do not credit just 'change in temperature'
1
(iv)
neutralisation
accept neutralise
accept neutral
accept formation of salt or water
do not credit exothermic
1
[4]
M8.
(a) all lead nitrate reacted
or no lead nitrate left
or enough KI to react with lead nitrate
or to remove all the lead ions
or to get maximum amount of I2
ignore comments about speed
do not accept to remove all the lead
1
(b)
precipitate
allow phonetic spelling
do not accept ppt
1
1
(c)
filter / filtration / centrifuge / decant
do not accept sieve
(d)
any one from:
•
removes (soluble) impurities
•
removes (unreacted) KI
•
removes KNO3
•
removes (excess) solution
•
removes nitrates
purifying is insufficient
do not accept removes potassium
do not accept removes iodide
1
(e)
answer based on filter paper, desiccator, suitable solvent
(gentle) heat, drying cabinet, oven etc.
Accept any method of heating i.e.
bunsen / hairdryer etc.
Accept leave to evaporate / stand or leave in a warm room
e.g. place between dry filter paper, allow to dry
e.g. use propanone, allow to dry
e.g. leave on sunny window sill
e.g. leave in a draught
the answer leave / evaporate /
draught alone is insufficient
1
(f)
wear gloves / mask
or fume-cupboard
or wash hands afterwards
ignore goggles / labcoat or extractor fan / do not touch etc.
1
[6]
M9.
(a)
sodium ions and chloride ions (not chlorine)
allow sodium chloride/salt/common salt
for 1 mark
1
(b)
H+ + OH– →H2O
H+ from (hydrochloric) acid
OH- from alkali/sodium hydroxide
lose 1 mark if no charge shown disregard other ions
each for 1 mark
3
[4]
C2.7 Electrolysis Revision Foundation
Q1.
The electrolysis of sodium chloride solution produces useful substances.
(a)
(i)
Choose a word from the box to complete the sentence.
covalent
ionic
non-metallic
Electrolysis takes place when electricity passes through ..................................
compounds when they are molten or in solution.
(1)
(ii)
Choose a word from the box to complete the sentence.
alkenes
elements
salts
During electrolysis the compound is broken down to form...............................
(1)
(b)
The diagram shows an apparatus used for the electrolysis of sodium chloride solution.
Identify the products A, B and C on the diagram using substances from the box.
chlorine gas
sodium hydroxide solution
(i)
hydrogen gas
oxygen gas
sodium metal
A is ....................................................................................................................
(1)
(ii)
B is ....................................................................................................................
(1)
(iii)
C is ....................................................................................................................
(1)
(Total 5 marks)
Q2.
A student investigated the electrolysis of lead bromide.
Lead bromide was placed in the tube and the circuit was switched on. The light bulb did not light up.
The tube was heated and soon the bulb lit up. The observations are shown in the table.
(a)
Positive electrode
Negative electrode
red-brown gas
silver liquid
What is meant by electrolysis?
....................................................................................................................................
(2)
(b)
Why did the lead bromide conduct electricity when the tube was heated?
....................................................................................................................................
(1)
(c)
Name the substances formed at the:
positive electrode; .....................................................................................................
negative electrode. ....................................................................................................
(2)
(d)
Suggest one safety precaution that should be taken during this investigation.
....................................................................................................................................
(1)
(Total 6 marks)
Q3.
Electrolysis can be used to remove unwanted hair from the skin.
The positive electrode is connected by a patch to the skin.
The negative electrode is connected to the hair.
The body fluid is a solution that contains sodium chloride. The electricity causes the
electrolysis of a small amount of this solution.
(a)
In this solution hydrogen ions move to the negative electrode.
Complete the sentence using one word from the box.
negative
neutral
positive
Hydrogen ions move to the negative electrode because they have a
....................................................... charge.
(1)
(b)
Draw a ring around the name of the gas produced at the positive electrode during the
electrolysis of sodium chloride solution.
chlorine
hydrogen
nitrogen
(1)
(c)
The electrolysis of the sodium chloride solution forms a strong alkali around the hair follicle.
(i)
Complete the name of this strong alkali using one of the words from the box.
chlorine
hydrogen
nitrogen
The name of this strong alkali is sodium ............................................ .
(1)
(ii)
Suggest how this strong alkali helps to remove the hair.
...........................................................................................................................
...........................................................................................................................
(1)
(Total 4 marks)
Q4.
The electrolysis of sodium chloride solution is an important industrial process. The apparatus
shown below can be used to show this electrolysis in the laboratory.
(a)
Name gas A. ...............................................................................................................
(1)
(b)
Chlorine is produced at the positive electrode. Describe and give the result of a chemical test to
prove that the gas is chlorine.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(c)
Chloride ions move to the positive electrode. Explain why.
.....................................................................................................................................
.....................................................................................................................................
(1)
(d)
A small quantity of chlorine is added to drinking water. Explain why.
.....................................................................................................................................
.....................................................................................................................................
(1)
(e)
The solution around the negative electrode becomes alkaline. Name the ion which makes the
solution alkaline.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 6 marks)
Q5.
Read the information in the box and then answer the question.
Aluminium is made by the electrolysis of aluminium oxide.
Aluminium oxide is an ionic compound containing aluminium ions (Al3+) and oxide ions
(O2–).
The diagram below shows the apparatus used to electrolyse aluminium oxide.
(a)
In this question you will get marks on using good English, organising information clearly and
using specialist terms correctly.
Use information in the box and your knowledge and understanding of this process to answer this
question. Explain, as fully as you can, how aluminium and carbon dioxide are formed in this
process.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(6)
(b)
Explain why cryolite is added.
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)
M1.
(a)
(i)
ionic
1
(ii)
elements
1
(b)
(i)
chlorine (gas)
allow Cl2 / Cl / Cl2
allow chloride
1
(ii)
hydrogen (gas)
allow H / H2 / H2
1
(iii)
sodium hydroxide (solution)
allow NaOH
allow sodium solution
1
[5]
M2.
(a)
breakdown / decomposition / splits into elements /
not ions
separates into elements / produce a chemical reaction
1
using electricity
1
(b)
lead bromide melted / free ions
not electrolyte
1
(c)
(+) bromine
element must be appropriate to electrode
1
(–) lead
element must be appropriate to electrode
1
(d)
fume cupboard / protective clothing
allow safety glasses
not safety mat
1
[6]
M3.
(a)
positive
accept + or +ve or plus
1
(b)
chlorine
1
(c)
(i)
hydroxide
Any indication of hydro…
1
(ii)
destroys / damages / dissolves (owtte) the hair / follicle / root
allow burns / reacts with the hair
ignore incorrect name of compound
1
[4]
M4.
(a)
hydrogen
accept H2
do not accept H
1
(b)
litmus paper / Universal Indicator paper / pH paper
allow any suitable named indicator
1
bleached / turns white or loses its colour
do not accept bleached cloth / leaves etc.
allow second mark unless incorrect indicator given
allow starch iodide paper (1)
goes black / blue black (1)
allow potassium iodide solution (1) goes brown / orange / black
precipitate (1)
1
(c)
because they have a negative charge or opposite charges attract
accept (because) it is Cl–
accept chlorine, Cl or chlorine ions has a negative charge
do not accept Cl– on its own
do not accept Cl2 o.e. has negative charge
1
(d)
kill bacteria / germs, etc. or sterilise / disinfect
accept destroys bacteria etc.
ignore clean / purify water (owtte)
do not accept just gets rid of bacteria
1
(e)
hydroxide (ion)
accept OH–
1
[6]
M5.
(a) Marks awarded for this answer will be determined by the Quality
of Written Communication (QWC) as well as the standard of the
scientific response.
No relevant content.
0 marks
There is a brief description of the electrolysis of aluminium oxide.
Level 1 (1–2 marks)
There is some description of the electrolysis of aluminium oxide.
Level 2 (3–4 marks)
There is a clear, balanced and detailed description of the
electrolysis of aluminium oxide.
Level 3 (5–6 marks)
examples of the chemistry points made in the response
•
aluminium oxide is melted / made liquid
•
aluminium ions are attracted to the negative electrode
•
at the negative electrode aluminium is formed or
aluminium ions gain electrons
•
oxide ions are attracted to the positive electrode
•
oxygen is formed at the positive electrode or oxide
ions lose electrons
•
the oxygen reacts with carbon to make carbon dioxide or
carbon dioxide formed at positive electrode.
(b)
Lowers melting point
1.
Less energy/electricity needed
1
Saves money
1