Q1.
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.
Page 1
Energy is taken in from the surroundings.
No energy is given out to or taken from the surroundings.
(1)
(Total 3 marks)
Q2.
An airship caught fire when it was coming in to land in 1937. The airship was filled with
hydrogen. A spark or flame ignited the hydrogen. The hydrogen reacted with oxygen in
the air to produce water.
(a)
Write a word equation for the reaction of hydrogen with oxygen.
............................................................................................................................. ........
(1)
(b)
Draw a ring around the correct answer in each box to complete this sentence.
released
When reactions take place, energy is
to break the existing bonds
supplied
released
and energy is
when new bonds form.
supplied
(1)
(c)
An energy level diagram for the reaction of hydrogen and oxygen is shown below.
Page 2
Use the energy level diagram above to help you to answer these questions.
(i)
Which energy change, A, B or C, represents the activation energy?
(1)
(ii)
Which energy change, A, B or C, shows that the reaction is exothermic?
(1)
(iii)
Explain why the hydrogen and oxygen needed a spark or flame to start the
reaction.
...........................................................................................................................
...........................................................................................................................
(1)
(Total 5 marks)
Q3.
Methanol can be made when methane reacts with oxygen.
(a)
The energy level diagram for this reaction is shown below.
Page 3
(i)
What is the energy change represented by A?
...............................................................................................................
(1)
(ii)
Use the energy level diagram to explain how it shows that this reaction is
exothermic.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(b)
A student did an experiment to find the energy released when methanol burns in air.
The student:
•
•
•
weighed a spirit burner containing methanol
set up the equipment as shown in the diagram
recorded the initial temperature
Page 4
•
•
•
•
lit the spirit burner
put out the flame when the temperature of the water had risen by
about 20 °C
stirred the water and recorded the highest temperature of the water
reweighed the spirit burner containing the methanol.
The student repeated the experiment and recorded his results.
Experiment 1
Experiment 2
Experiment 3
Initial mass of spirit burner and
methanol in g
299.3
298.3
296.9
Final mass of spirit burner and
methanol in g
298.3
297.1
295.9
Initial temperature
in °C
23
22
23
Highest temperature
in °C
45
50
43
Temperature change
in °C
22
28
20
Use the diagram and the information in the table to answer the questions.
(i)
The main error in this experiment is energy loss.
Suggest one way that the equipment could be changed to reduce energy loss.
...............................................................................................................
(1)
Page 5
(ii)
The temperature change in Experiment 2 is greater than the temperature
change in Experiment 1 and Experiment 3.
Explain why.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(iii)
Suggest one reason why the student repeated the experiment.
................................................................................................... ............
...............................................................................................................
(1)
(iv)
Use the temperature change in Experiments 1 and 3 to calculate how much
energy is released when 1g of methanol burns. The equation that you need to
use is:
Energy released in joules = 100 x 4.2 x mean temperature change
Show clearly how you work out your answer.
............................................................................................................. ..
...............................................................................................................
...............................................................................................................
Burning 1g of methanol releases ...................................... J
(2)
(Total 9 marks)
Q4.
(a)
(i)
Which acid should the student add to sodium hydroxide solution to make
sodium sulphate?
............................................................. acid
(1)
Page 6
(ii)
Use the table on the Data Sheet to help you to write the formula of sodium
sulphate.
Formula: ...........................................................................................................
(1)
(b)
The student noticed that the solution in the beaker got warm when the acid reacted
with the alkali.
The energy diagram below represents this reaction.
Page 7
(i)
In terms of energy, what type of reaction is this?
..........................................................................................................................
(1)
(ii)
Use the energy diagram to calculate a value for the amount of energy
released during this reaction.
..........................................................................................................................
Energy released .................... kJ
(1)
(iii)
Explain, in terms of bond breaking and bond forming, why energy is released
during this reaction.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(iv)
The reaction takes place very quickly, without the help of a catalyst. What
does this suggest about the activation energy for this reaction?
...........................................................................................................................
.................................................................................................................... .......
(1)
(Total 8 marks)
Page 8
M1.
(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]
M2.
(a)
hydrogen + oxygen → water
accept 2H2 + O2 → 2H2O or balanced multiples or fractions
allow 1 or 2 correct formulae substituted for words
allow hydrogen oxide or steam for water
1
(b)
supplied
released
both needed, must be in this order
1
(c)
(i)
B
1
(ii)
A
1
(iii)
to overcome activation energy to react or (activation) energy needed to start
reaction
allow to provide energy
1
[5]
Page 9
M3.
(a)
(i)
activation energy or energy needed to start the reaction
1
(ii)
the reaction is exothermic because the energy level /
value of products is less than the energy level /
value of reactants
allow the reaction is exothermic because arrow B goes down
or methanol is below methane and oxygen
or arrow C is bigger than arrow A for 1 mark
allow energy level of products is lower unqualified
or the energy level of reactants is higher unqualified for 1
mark
2
(b)
(i)
use a lid / cover over the calorimeter
or any mention of how the calorimeter could be safely
enclosed / insulated
1
(ii)
a greater mass of methanol was burned in Experiment 2
1
therefore the temperature change was greater because
more energy was transferred / released
1
(iii)
any one from:
•
to improve or check repeatability / quality of results
•
to make it easier to spot an anomalous measurement
•
to be able to calculate an average mean value
1
(iv)
8820 (J)
for correct answer
if answer is incorrect allow one mark for 21 used as the
Page 10
mean temperature change
2
[9]
M4.
(a)
(i)
sulphuric acid / H2SO4 (accept sulfuric)
for one mark
1
(ii)
Na2SO4 / (Na)2SO4 / Na2(SO4) / (Na+)2SO42–
for one mark
lower case O ( Na2So4) not accepted/tops of subscripted numbers should
be in line with or lower than lower case letters of symbols / upper case ‘a’
not accepted
1
(b)
(i)
exothermic
for one mark
1
(ii)
60 KJ
for one mark
1
(iii)
energy given out when bonds form
energy taken in when bonds break
energy given out is greater then energy taken in (owtte)
for 1 mark each
3
(iv)
activation energy is low / many molecules have enough energy to react
for one mark
1
[8]
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