chem

1. The graph below shows how the volume of carbon dioxide formed varies with time when a

hydrochloric acid solution is added to excess calcium carbonate in a flask.

(i) Explain the shape of the curve.(3)

(ii) Copy the above graph on your answer sheet and sketch the curve you would obtain if

double the volume of hydrochloric acid solution of half the concentration as in the

example above is used instead, with all other variables kept constant from the original.

Explain why the shape of the curve is different.(4)

(iii) Outline one other way in which the rate of this reaction can be studied in a school

laboratory. Sketch a graph to illustrate how the selected variable would change with time.(2)

(iv) Define the term activation energy and state one reason why the reaction between calcium

carbonate and hydrochloric acid takes place at a reasonably fast rate at room temperature.(2)

(Total 11 marks)

IB Questionbank Chemistry 1

2. The following data were obtained for the reaction between gases A and B.

Experiment Initial [A] / mol dm–3 Initial [B] / mol dm–3 Initial rate / mol dm–3 min–1

1 1.0 × 10–3 1.0 × 10–3 2.0 × 10–4

2 2.0 × 10–3 1.0 × 10–3 2.0 × 10–4

3 2.0 × 10–3 2.0 × 10–3 4.0 × 10–4

Which relationship represents the rate expression for the reaction?

A. rate = k[B]2

B. rate = k[A]2

C. rate = k[A]

D. rate = k[B](Total 1 mark)

3. Consider the following reactions.

Cu2O(s) +

O2(g) → 2CuO(s) 2HO = –144 kJ2

1

Cu2O(s) → Cu(s) + CuO(s) 2HO = +11 kJ

What is the value of 2HO, in kJ, for this reaction?

Cu(s) +

O2(g) → CuO(s)2

1

A. –144 + 11

B. +144 – 11

C. –144 – 11

D. +144 + 11(Total 1 mark)


4. The equilibrium between nitrogen dioxide, NO2, and dinitrogen tetroxide, N2O4, is shown

below.

2NO2(g) N2O4(g) Kc = 0.01

What happens when the volume of a mixture at equilibrium is decreased at a constant

temperature?

I. The value of Kc increases

II. More N2O4 is formed

III. The ratio of

decreases]ON[

]NO[

42

2

A. I and II only

B. I and III only

C. II and III only

D. I, II and III(Total 1 mark)


5. Sodium thiosulfate solution, Na2S2O3(aq), and hydrochloric acid, HCl(aq), react spontaneously

to produce solid sulfur, S(s), according to the equation below.

S2O32–(aq) + 2H+(aq) → S(s) + SO2(aq) + H2O(l)

A student experimentally determined the rate expression to be:

rate = k[S2O32–(aq)]2

Which graph is consistent with this information?

(Total 1 mark)

6. Propene can be hydrogenated in the presence of a nickel catalyst to form propane.

Use the data below to answer the questions that follow.

Compound Formula ∆HOf / kJ mol–1 S

O/ J K

–1 mol

–1

hydrogen H2(g) 0 + 131

propane C3H8(g) – 104 + 270

propene C3H6(g) + 20.4 + 267


(i) Outline why the value for the standard enthalpy change of formation of hydrogen is zero.

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(ii) Calculate the standard enthalpy change for the hydrogenation of propene.

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(iii) Calculate the standard entropy change for the hydrogenation of propene.

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(iv) Determine the value of 2GO for the hydrogenation of propene at 298 K.

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(v) At 298 K the hydrogenation of propene is a spontaneous process. Determine the

temperature above which propane will spontaneously decompose into propene and

hydrogen.

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(Total 9 marks)

7. Bromine and nitrogen(II) oxide react according to the following equation.

Br2(g) + 2NO(g) → 2NOBr(g)

Which rate equation is consistent with the experimental data?

[Br2] / mol dm–3 [NO] / mol dm–3 Rate / mol dm–3 s–1

0.10 0.10 1.0 × 10–6

0.20 0.10 4.0 × 10–6

0.20 0.40 4.0 × 10–6

A. rate = k[Br2]2 [NO]

B. rate = k[Br2] [NO]2

C. rate = k[Br2]2

D. rate = k[NO]2

(Total 1 mark)

8. Methanol may be produced by the exothermic reaction of carbon monoxide gas and hydrogen

gas.

CO(g) + 2H2(g) CH3OH(g) 2HO = –103 kJ


(a) State the equilibrium constant expression, Kc, for the production of methanol.

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(b) State and explain the effect of changing the following conditions on the amount of

methanol present at equilibrium:

(i) increasing the temperature of the reaction at constant pressure.

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(ii) increasing the pressure of the reaction at constant temperature.

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(c) The conditions used in industry during the production of methanol are a temperature of

450 °C and pressure of up to 220 atm. Explain why these conditions are used rather than

those that could give an even greater amount of methanol.

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(d) A catalyst of copper mixed with zinc oxide and alumina is used in industry for this

production of methanol. Explain the function of the catalyst.

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(Total 8 marks)

9. If white anhydrous copper(II) sulfate powder is left in the atmosphere it slowly absorbs water

vapour giving the blue pentahydrated solid.

CuSO4(s) + 5H2O(l) → CuSO4•5H2O(s)

(anhydrous) (pentahydrated)

It is difficult to measure the enthalpy change for this reaction directly. However, it is possible

to measure the heat changes directly when both anhydrous and pentahydrated copper(II) sulfate

are separately dissolved in water, and then use an energy cycle to determine the required

enthalpy change value, 2Hx, indirectly.


(a) To determine 2H1 a student placed 50.0 g of water in a cup made of expanded

polystyrene and used a data logger to measure the temperature. After two minutes she

dissolved 3.99 g of anhydrous copper(II) sulfate in the water and continued to record the

temperature while continuously stirring. She obtained the following results.

(i) Calculate the amount, in mol, of anhydrous copper(II) sulfate dissolved in the 50.0

g of water.

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(ii) Determine what the temperature rise would have been, in °C, if no heat had been

lost to the surroundings.

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(iii) Calculate the heat change, in kJ, when 3.99 g of anhydrous copper(II) sulfate is

dissolved in the water.

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(iv) Determine the value of 2H1 in kJ mol–1.

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(b) To determine 2H2, 6.24 g of pentahydrated copper(II) sulfate was dissolved in 47.75 g of

water. It was observed that the temperature of the solution decreased by 1.10 °C.

(i) Calculate the amount, in mol, of water in 6.24 g of pentahydrated copper(II)

sulfate.

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(ii) Determine the value of 2H2 in kJ mol–1.

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(iii) Using the values obtained for 2H1 in (a) (iv) and 2H2 in (b) (ii), determine the

value for 2Hx in kJ mol–1.

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(c) The magnitude (the value without the + or – sign) found in a data book for 2Hx is

78.0 kJ mol–1.

(i) Calculate the percentage error obtained in this experiment. (If you did not obtain

an answer for the experimental value of 2Hx then use the value 70.0 kJ mol–1, but

this is not the true value.)

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(ii) The student recorded in her qualitative data that the anhydrous copper(II) sulfate

she used was pale blue rather than completely white. Suggest a reason why it

might have had this pale blue colour and deduce how this would have affected the

value she obtained for 2Hx.

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(Total 14 marks)

10. In an experiment to measure the enthalpy change of combustion of ethanol, a student heated a

copper calorimeter containing 100 cm3 of water with a spirit lamp and collected the following

data.

Initial temperature of water: 20.0 °C

Final temperature of water: 55.0 °C

Mass of ethanol burned: 1.78 g

Density of water: 1.00 g cm–3

(i) Use the data to calculate the heat evolved when the ethanol was combusted.(2)

(ii) Calculate the enthalpy change of combustion per mole of ethanol.(2)


(iii) Suggest two reasons why the result is not the same as the value in the Data Booklet.(2)

(Total 6 marks)

11. One important property of a rocket fuel mixture is the large volume of gaseous products formed

which provide thrust. Hydrazine, N2H4, is often used as a rocket fuel. The combustion of

hydrazine is represented by the equation below.

N2H4(g) + O2(g) → N2(g) + 2H2O(g) 2HcO = –585 kJ mol–1

(a) Hydrazine reacts with fluorine to produce nitrogen and hydrogen fluoride, all in the

gaseous state. State an equation for the reaction.

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(b) Draw the Lewis structures for hydrazine and nitrogen.

(2)


(c) Use the average bond enthalpies given in Table 10 of the Data Booklet to determine the

enthalpy change for the reaction in part (a) above.

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(d) Based on your answers to parts (a) and (c), suggest whether a mixture of hydrazine and

fluorine is a better rocket fuel than a mixture of hydrazine and oxygen.

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(Total 9 marks)

12. Which reaction has the most negative change in entropy?

A. 2SO2(g) + O2(g) → 2SO3(g)

B. NH4Cl(s) → NH3(g) + HCl(g)

C. PbCl2(s) → Pb2+(aq) + 2Cl–(aq)

D. C(s) + O2(g) → CO2(g)

(Total 1 mark)


13. A reaction has a standard enthalpy change, ∆HO, of +10.00 kJ mol–1 at 298 K. The standard

entropy change, ∆SO, for the same reaction is +10.00 J K–1 mol–1. What is the value of ∆GO for

the reaction in kJ mol–1?

A. +9.75

B. +7.02

C. –240

D. –2970(Total 1 mark)

14. Consider the following reaction.

5Br–(aq) + BrO3–(aq) + 6H+(aq) → 3Br2(aq) + 3H2O(l)

The rate expression for the reaction is found to be:

rate = k[Br–] [BrO3–][H+]2

Which statement is correct?

A. The overall order is 12.

B. Doubling the concentration of all of the reactants at the same time would increase the

rate of the reaction by a factor of 16.

C. The units of the rate constant, k, are mol dm–3 s–1.

D. A change in concentration of Br– or BrO3– does not affect the rate of the reaction.

(Total 1 mark)


15. For the following reaction Kc = 1.0 × 10–5 at 30 °C.

2NOCl(g) 2NO(g) + Cl2(g)

Which relationship is correct at equilibrium at this temperature?

A. The concentration of NO equals the concentration of NOCl.

B. The concentration of NOCl is double the concentration of Cl2.

C. The concentration of NOCl is much greater than the concentration of Cl2.

D. The concentration of NO is much greater than the concentration of NOCl.(Total 1 mark)

16. An example of a homogeneous reversible reaction is the reaction between hydrogen and iodine.

H2(g) + I2(g) 2HI(g)

(i) Outline the characteristics of a homogeneous chemical system that is in a state of

equilibrium.

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(ii) Deduce the expression for the equilibrium constant, Kc.

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(iii) Predict what would happen to the position of equilibrium and the value of Kc if the

pressure is increased from 1 atm to 2 atm.

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(iv) The value of Kc at 500 K is 160 and the value of Kc at 700 K is 54. Deduce what this

information tells us about the enthalpy change of the forward reaction.

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(v) The reaction can be catalysed by adding platinum metal. State and explain what effect

the addition of platinum would have on the value of the equilibrium constant.

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(Total 8 marks)


17. Curve X on the graph below shows the volume of oxygen formed during the catalytic

decomposition of a 1.0 mol dm–3 solution of hydrogen peroxide.

2H2O2(aq) → O2(g) + 2H2O(l)

Which change would produce the curve Y?

A. Adding water

B. Adding some 0.1 mol dm–3 hydrogen peroxide solution

C. Using a different catalyst

D. Lowering the temperature(Total 1 mark)

18. 0.50 mol of I2(g) and 0.50 mol of Br2(g) are placed in a closed flask. The following equilibrium

is established.

I2(g) + Br2(g) IBr(g)

The equilibrium mixture contains 0.80 mol of IBr(g). What is the value of Kc?

A. 0.64

B. 1.3

C. 2.6

D. 64(Total 1 mark)


19. Consider the following equilibrium.

2SO2(g) + O2(g) 2SO3(g) ∆Ho = –198 kJ mol–1

(i) Deduce the equilibrium constant expression, Kc, for the reaction.

(1)

(ii) State and explain the effect of increasing the temperature on the yield of sulfur trioxide.(2)

(iii) State the effect of a catalyst on the value of Kc.

(1)

(iv) State and explain the effect of a catalyst on the position of equilibrium.(2)

(Total 6 marks)

20. The Haber process enables the large-scale production of ammonia needed to make fertilizers.

The equation for the Haber process is given below.

N2(g) + 3H2 2NH3(g)

The percentage of ammonia in the equilibrium mixture varies with temperature.

(i) Use the graph to deduce whether the forward reaction is exothermic or endothermic and

explain your choice.(2)


(ii) State and explain the effect of increasing the pressure on the yield of ammonia.(2)

(iii) Explain the effect of increasing the temperature on the rate of reaction.(2)

(Total 6 marks)


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