Chemistry 12 (HL)
Mock Exam Review
IB Chemistry Paper 2 “Data Based Questions” (Past Papers)
May 2010 – TZ1
1.
Brass is a copper containing alloy with many uses. An analysis is carried out to determine
the percentage of copper present in three identical samples of brass. The reactions involved
in this analysis are shown below.
(a) (i) Deduce the change in the oxidation numbers of copper and nitrogen in step 1.
(ii) Identify the oxidizing agent in step 1. [1]
[2]
(b) A student carried out this experiment three times, with three identical small brass nails,
and obtained the following results.
Mass of brass = 0.456 g ± 0.001 g
(i) Calculate the average amount, in mol, of S2O32- added in step 3. [2]
(ii) Calculate the amount, in mol, of copper present in the brass. [1]
(iii) Calculate the mass of copper in the brass. [1]
(iv) Calculate the percentage by mass of copper in the brass. [1]
(v) The manufacturers claim that the sample of brass contains 44.2 % copper by mass.
Determine the percentage error in the result. [1]
(c) In step 1 the copper reacts to form a blue solution.
(i) State the full electronic configuration of Cu2+. [1]
(ii) Explain why the copper solution is coloured. [2]
May 2010 – TZ2
1.
The percentage by mass of calcium carbonate in eggshell was determined by adding excess
hydrochloric acid to ensure that all the calcium carbonate had reacted. The excess acid left
was then titrated with aqueous sodium hydroxide.
(a) A student added 27.20 cm3 of 0.200 mol dm-3 HCl to 0.188 g of eggshell. Calculate the
amount, in mol, of HCl added. [1]
Chemistry 12 (HL)
Mock Exam Review
(b) The excess acid requires 23.80 cm3 of 0.100 mol dm-3 NaOH for neutralization.
Calculate the amount, in mol, of acid that is in excess. [1]
(c) Determine the amount, in mol, of HCl that reacted with the calcium carbonate in
the eggshell. [1]
(d) State the equation for the reaction of HCl with the calcium carbonate in the eggshell.
[2]
(e) Determine the amount, in mol, of calcium carbonate in the sample of the eggshell. [2]
(f) Calculate the mass and the percentage by mass of calcium carbonate in the
eggshell sample. [3]
(g) Deduce one assumption made in arriving at the percentage of calcium carbonate in
the eggshell sample. [1]
Nov 2009
1.
The data below is from an experiment used to determine the percentage of iron present
in a sample of iron ore. This sample was dissolved in acid and all of the iron was converted
to Fe2+. The resulting solution was titrated with a standard solution of potassium
manganate(VII), KMnO4. This procedure was carried out three times. In acidic solution,
MnO4- reacts with Fe2+ ions to form Mn2+ and Fe3+ and the end point is indicated by a slight
pink colour.
(a) Deduce the balanced redox equation for this reaction in acidic solution. [2]
(b) Identify the reducing agent in the reaction. [1]
(c) Calculate the amount, in moles, of MnO4- used in the titration. [2]
(d) Calculate the amount, in moles, of Fe present in the 3.682×10-1 g sample of iron ore.
[2]
(e) Determine the percentage by mass of Fe present in the 3.682×10-1 g sample of iron ore.
[2]
Chemistry 12 (HL)
Mock Exam Review
May 2009 – TZ1
1.
Biodiesel makes use of plants’ ability to fix atmospheric carbon by photosynthesis.
Many companies and individuals are now using biodiesel as a fuel in order to reduce
their carbon footprint. Biodiesel can be synthesized from vegetable oil according to the
following reaction.
(a)
Identify the organic functional group present in both vegetable oil and biodiesel.
[1]
(b) For part of her extended essay investigation into the efficiency of the process, a student
reacted a pure sample of a vegetable oil (where R = C17H33) with methanol. The raw
data recorded for the reaction is below.
Mass of oil = 1013.0 g
Mass of methanol = 200.0 g
Mass of sodium hydroxide = 3.5 g
Mass of biodiesel produced = 811.0 g
The relative molecular mass of the oil used by the student is 885.6. Calculate the
amount (in moles) of the oil and the methanol used, and hence the amount (in moles)
of excess methanol. [3]
(c) The reversible arrows in the equation indicate that the production of biodiesel is an
equilibrium process.
(i)
State what is meant by the term dynamic equilibrium. [1]
(ii) Using the abbreviations [vegetable oil], [methanol], [glycerol] and [biodiesel]
deduce the equilibrium constant expression (Kc ) for this reaction. [1]
(iii) Suggest a reason why excess methanol is used in this process. [1]
(iv) State and explain the effect that the addition of the sodium hydroxide catalyst
will have on the position of equilibrium. [2]
(d) The reactants had to be stirred vigorously because they formed two distinct layers in
the reaction vessel. Explain why they form two distinct layers and why stirring
increases the rate of reaction. [2]
(e) Calculate the percentage yield of biodiesel obtained in this process. [2]
(f) When biodiesel is combusted it produces carbon dioxide. Explain why the use of
biodiesel as a fuel does not significantly contribute to global warming. [1]
Chemistry 12 (HL)
Mock Exam Review
May 2009 TZ 2 1. Aspirin, one of the most widely used drugs in the world, can be prepared according to
the equation given below.
(a) State the names of the three organic functional groups in aspirin. [3]
(b) A student reacted some salicylic acid with excess ethanoic anhydride. Impure solid
aspirin was obtained by filtering the reaction mixture. Pure aspirin was obtained by
recrystallization. The following table shows the data recorded by the student.
(i)
(ii)
(iii)
(iv)
(v)
(vi)
O2
Determine the amount, in mol, of salicylic acid, C6H4(OH)COOH, used. [2]
Calculate the theoretical yield, in g, of aspirin, C6H4(OCOCH3)COOH. [2]
Determine the percentage yield of pure aspirin. [1]
State the number of significant figures associated with the mass of pure aspirin
obtained, and calculate the percentage uncertainty associated with this mass. [2]
Another student repeated the experiment and obtained an experimental yield
of 150 %. The teacher checked the calculations and found no errors. Comment
on the result. [1]
The following is a three-dimensional computer-generated representation of
aspirin.
Chemistry 12 (HL)
Mock Exam Review
A third student measured selected bond lengths in aspirin, using this computer
program and reported the following data.
The following hypothesis was suggested by the student: “Since all the measured
carbon-carbon bond lengths are equal, all the carbon-oxygen bond lengths must
also be equal in aspirin. Therefore, the C8–O4 bond length must be 1.4 x 10-10 m”.
Comment on whether or not this is a valid hypothesis. [2]
(vii) The other product of the reaction is ethanoic acid, CH3COOH. Define an acid
according to the Brønsted-Lowry theory and state the conjugate base of CH3COOH.[2]
Specimen Paper 2009
1.
The data below is from an experiment used to measure the enthalpy change for the
combustion of 1 mole of sucrose (common table sugar), C12H22O11 (s). The time
temperature data was taken from a data-logging software programme.
Mass of sample of sucrose, m = 0.4385 g
Heat capacity of the system, Csystem = 10114 kJ K-1
(a)
Calculate ∆T, for the water, surrounding the chamber in the calorimeter. [1]
Chemistry 12 (HL)
Mock Exam Review
(b)
Determine the amount, in moles, of sucrose. [1]
(c)
(i)
(ii)
(d)
A hypothesis is suggested that TNT, 2-methyl-1,3,5-trinitrobenzene, is a powerful
explosive because it has:
• a large enthalpy of combustion
• a high reaction rate
• a large volume of gas generated upon combustion
Calculate the enthalpy change for the combustion of 1 mole of sucrose. [1]
Using Table 12 of the Data Booklet, calculate the percentage experimental
error based on the data used in this experiment. [1]
Use your answer in part (c)(i) and the following data to evaluate this hypothesis. [3]
May 2008 TZ1
1.
The value of x in Fe(NH4)2(SO4)2•xH2O can be found by determining the amount, in
moles, of sulfate in the compound.
A 0.982 g sample was dissolved in water and excess BaCl2(aq) was added.
The precipitate of BaSO4 was separated and dried and found to weigh 1.17 g.
(a) Calculate the amount, in moles of BaSO4 in the 1.17 g precipitate. [2]
(b) Calculate the amount, in moles, of sulfate in the 0.982 g sample of
Fe(NH4)2(SO4)2•xH2O [1]
(c) Calculate the amount, in moles, of iron in the 0.982 g sample of
Fe(NH4)2(SO4)2•xH2O. [1]
(d) Determine the mass of the following present in the 0.982 g sample of
Fe(NH4)2(SO4)2•xH2O .[3]
(i) Iron
(ii) Ammonium
(iii) Sulfate
(e) Use your answer from part (d) to determine the amount, in moles, of water present in
the 0.982g sample of Fe(NH4)2(SO4)2•xH2O. [2]
(f) Determine the amount, in moles, of Fe(NH4)2(SO4)2 and hence the value of x. [2]
Chemistry 12 (HL)
Mock Exam Review
May 2008 TZ2
1.
Hydrogen and nitrogen(II) oxide react together exothermically as follows.
2H2(g) + 2NO(g) à 2H2O(g) + N2(g)
The rate of this reaction was investigated in a series of experiments carried out at the
same temperature, the results of which are shown in the table below.
(a) Explain how the results from Experiments 1 and 2 can be used to deduce that the
order of reaction with respect to hydrogen is 1. [1]
(b) Deduce the order of reaction with respect to nitrogen(II) oxide, giving a reason
for your answer. [2]
(c) Use your answers from parts (a) and (b) to deduce the rate expression for the reaction.
[1]
(d) Complete the table above by calculating the rate of reaction for each of Experiments
3 and 5 (write your answers in the table). [2]
(e) Use the results from Experiment 1 to determine the value of, and the units for, the rate
constant, k, for the reaction. [2]
(f) Suggest a mechanism for the reaction that is consistent with the rate expression. [2]
(g) The reaction is faster in the presence of a heterogeneous catalyst. Explain the meaning
of the term heterogeneous as applied to a catalyst. Draw a labelled enthalpy level
diagram that shows the effect of the catalyst. [3]
Chemistry 12 (HL)
Mock Exam Review
November 2008
1.
(a) The diagram shows the apparatus used to study the rate of reaction between calcium
carbonate and hydrochloric acid.
CaCO3(s) + 2HCl(aq) à CaCl2(aq) + H2O(l) + CO2(g)
The quantities of reactants added to the flask in one experiment carried out at room
temperature were:
mass of single piece of CaCO3(s) = 5.00 g
volume of 1.00 mol dm-3 HCl (aq) = 50.0 cm3
The balance was set to zero at the start of the experiment.
The graph shows how the mass of the flask and contents changed during Experiment 1.
(i)
Explain why the mass decreased. [1]
(ii) Calculate the amount, in moles, of each reactant at the start of Experiment 1. [2]
(iii) Use your answers to (a) (ii), and the equation for the reaction, to deduce which
reactant was added in excess. [1]
(iv) The experiment was repeated with small pieces of calcium carbonate. Draw two
lines (labelled 2 and 3) on the graph to show how the mass of the flask and
contents changes in the following experiments at the same temperature. [4]
(b) For the reaction between compounds A and B the initial rate was measured in a series
of reactions carried out at the same temperature.
Chemistry 12 (HL)
Mock Exam Review
(i)
Deduce the order of reaction with respect to A and to B, giving a reason in
each case. [2]
(ii) Deduce the rate expression for the reaction. [1]
(iii) Use the data for Experiment 1 to determine the value, including units, of the rate
constant for the reaction. [2]
Nov 2007
(I would not consider this a good example of a data based question for the current syllabus, but
it is an example of a type of calculation you should be able to do.)
1.
0.502 g of an alkali metal sulfate is dissolved in water and excess barium chloride solution,
BaCl2(aq) is added to precipitate all the sulfate ions as barium sulfate, BaSO4 (s). The
precipitate is filtered and dried and weighs 0.672 g.
(a) Calculate the amount (in mol) of barium sulfate formed. [2]
(b) Determine the amount (in mol) of the alkali metal sulfate present. [1]
(c) Determine the molar mass of the alkali metal sulfate and state its units. [2]
(d) Deduce the identity of the alkali metal, showing your workings. [2]
(e) Write an equation for the precipitation reaction, including state symbols. [2]
May 2005
(I would not consider this a good example of a data based question for the current syllabus, but
it is an example of a more extended type of calculation you should be able to do.)
1.
The standard enthalpy change for the combustion of phenol, C6H5OH(s), is −3050 kJ mol−1
at 298 K.
(a) Write an equation for the complete combustion of phenol. [1]
(b) The standard enthalpy changes of formation of carbon dioxide, CO2, and of water,
H2O, are −394 kJ mol-1 and −286 kJ mol-1 respectively.
Calculate the standard enthalpy change of formation of phenol, C6H5OH(s). [3]
(c) The standard entropy change of formation, ΔSº , of phenol, C6H5OH(s), at 298 K is
−385 J K-1 mol-1. Calculate the standard free energy change of formation , Gº, of
Chemistry 12 (HL)
Mock Exam Review
phenol at 298 K. [3]
(d) Determine whether the reaction is spontaneous at 298 K, and give a reason. [2]
(e) Predict the effect, if any, of an increase in temperature on the spontaneity of this
reaction. [2]
From the Last Century …
1.
In order to determine the enthalpy change of reaction between zinc and copper (II) sulfate,
a student placed 50.0 cm3 of 0.200 mol dm-3 copper (II) sulfate solution in a polystyrene
beaker. The temperature was recorded every 30 seconds. After two minutes 1.20 g of
powdered zinc was added. The Solution was stirred and the temperature recorded every
half minute for the next 14 minutes. The results obtained were then plotted to give the
following graph:
a) Write the equation for the reaction taking place. [1]
b) Determine which of the two reagents was present in excess. [2]
c) The highest temperature is reached at point A. Explain what is happening in the
system at this point. [1]
d) By drawing a suitable line on the graph estimate what the rise in temperature would
have been if the reaction had taken place instantaneously. [2]
e) Calculate how much heat was evolved during the reaction. Give your answer to three
significant figures. [2]
f)
What is the enthalpy change of reaction in kJ mol-1? [1]
g) The accepted value for the enthalpy change of reaction is -218 kJ mol-1. What is the
percentage error for the value obtained n this experiment? [1]
h) Suggest two reasons why there is disagreement between the experimental value and
the accepted value. [2]