(Total 1 mark) - Chemistry is bae

1. When 100 cm3 of 1.0 mol dm–3 HCl is mixed with 100 cm3 of 1.0 mol dm–3 NaOH, the temperature of the resulting solution increases by 5.0 °C. What will be the temperature change, in °C, when 50 cm3 of these two solutions are mixed?

A. 2.5

B. 5.0

C. 10

D. 20 (Total 1 mark)

2. Consider the following reactions.

N2(g) + O2(g) → 2NO(g) ∆HO = +180 kJ 2NO2(g) → 2NO(g) + O2(g) ∆HO = +112 kJ

What is the ∆HO value, in kJ, for the following reaction?

N2(g) + 2O2(g) → 2NO2(g)

A. –1 × (+180) + –1 × (+112)

B. –1 × (+180) + 1 × (+112)

C. 1 × (+180) + –1 × (+112)

D. 1 × (+180) + 1 × (+112) (Total 1 mark)

IB Questionbank Chemistry 1

3. Which statement is correct given the enthalpy level diagram below?

A. The reaction is endothermic and the products are more thermodynamically stable than the reactants.

B. The reaction is exothermic and the products are more thermodynamically stable than the reactants.

C. The reaction is endothermic and the reactants are more thermodynamically stable than the products.

D. The reaction is exothermic and the reactants are more thermodynamically stable than the products.

(Total 1 mark)

4. Which equation best represents the bond enthalpy of HCl?

A. HCl(g) → H+(g) + Cl–(g)

B. HCl(g) → H(g) + Cl(g)

C. HCl(g) → 21 H2(g) + 2

1 Cl2(g)

D. 2HCl(g) → H2(g) + Cl2(g) (Total 1 mark)


5. Which equation corresponds to the lattice enthalpy for silver iodide, AgI?

A. AgI(s) → Ag(s) + I(g)

B. AgI(s) → Ag(s) + 21 I2(g)

C. AgI(s) → Ag+(aq) + I–(aq)

D. AgI(s) → Ag+(g) + I–(g) (Total 1 mark)

6. When hydrogen peroxide decomposes, the temperature of the reaction mixture increases.

2H2O2(aq) → O2(g) + 2H2O(l)

What are the signs of ∆H, ∆S and ∆G for this reaction?

∆H ∆S ∆G

A. – – –

B. – + –

C. + + –

D. – + + (Total 1 mark)

7. Which change will not increase the entropy of a system?

A. Increasing the temperature

B. Changing the state from liquid to gas

C. Mixing different types of particles

D. A reaction where four moles of gaseous reactants changes to two moles of gaseous products

(Total 1 mark)


8. Which combination of ionic radius and ionic charge would result in the highest lattice enthalpy for an ionic compound?

Ionic radius Ionic charge

A. small high

B. large high

C. small low

D. large low (Total 1 mark)

9. What is the standard entropy change, ∆SO, for the following reaction?

2CO(g) + O2(g) → 2CO2(g)

CO(g) O2(g) CO2(g)

SO/J K–1 mol–1 198 205 214

A. –189

B. –173

C. +173

D. +189 (Total 1 mark)

10. Which reaction has the most negative ∆Hο value?

A. LiF(s) → Li+(g) + F–(g)

B. Li+(g) + F–(g) → LiF(s)

C. NaCl(s) → Na+(g) + Cl–(g)

D. Na+(g) + Cl–(g) → NaCl(s) (Total 1 mark)


11. 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)


12. The data below are from an experiment to measure the enthalpy change for the reaction of aqueous copper(II) sulfate, CuSO4(aq) and zinc, Zn(s).

Cu2+(aq) + Zn(s) → Cu(s) + Zn2+(aq)

50.0 cm3 of 1.00 mol dm–3 copper(II) sulfate solution was placed in a polystyrene cup and zinc powder was added after 100 seconds. The temperature-time data was taken from a data-logging software program. The table shows the initial 23 readings.

A straight line has been drawn through some of the data points. The equation for this line is given by the data logging software as

T = –0.050t + 78.0

where T is the Temperature at time t.


(a) The heat produced by the reaction can be calculated from the temperature change, ΔT, using the expression below.

Heat change = Volume of CuSO4(aq) × Specific heat capacity of H2O × ∆T

Describe two assumptions made in using this expression to calculate heat changes.

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...................................................................................................................................... (2)

(b) (i) Use the data presented by the data logging software to deduce the temperature change, ∆T, which would have occurred if the reaction had taken place instantaneously with no heat loss.

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........................................................................................................................... (2)

(ii) State the assumption made in part (b)(i).

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........................................................................................................................... (1)

(iii) Calculate the heat, in kJ, produced during the reaction using the expression given in part (a).

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........................................................................................................................... (1)


(c) The colour of the solution changed from blue to colourless. Deduce the amount, in moles, of zinc which reacted in the polystyrene cup.

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...................................................................................................................................... (1)

(d) Calculate the enthalpy change, in kJ mol–1, for this reaction.

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...................................................................................................................................... (1)

(Total 8 marks)

13. In some countries, ethanol is mixed with gasoline (petrol) to produce a fuel for cars called gasohol.

(i) Define the term average bond enthalpy. (2)

(ii) Use the information from Table 10 of the Data Booklet to determine the standard enthalpy change for the complete combustion of ethanol.

CH3CH2OH(g) + 3O2(g) → 2CO2(g) + 3H2O(g) (3)

(iii) The standard enthalpy change for the complete combustion of octane, C8H18, is –5471 kJ mol–1. Calculate the amount of energy produced in kJ when 1 g of ethanol and 1 g of octane is burned completely in air.

(2) (Total 7 marks)

14. (i) Define the terms lattice enthalpy and electron affinity. (2)


(ii) Use the data in the following table and from the data booklet to construct the Born-Haber cycle for sodium chloride, NaCl, and determine the lattice enthalpy of NaCl(s).

Na(s) + 21 Cl2(g) → NaCl(g) ∆Hο = –411 kJ mol–1

Na(s) → Na(g) ∆Hο = +108 kJ mol–1

(4)

(iii) Describe the structure of sodium chloride. (2)

(Total 8 marks)

15. Which statements describe the action of a catalyst?

I. It does not alter the ∆H for a reaction.

II. It increases the Ea for the reaction.

III. It alters the mechanism (pathway) of a reaction.

A. I and II only

B. I and III only

C. II and III only

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


16. Consider the reaction between gaseous iodine and gaseous hydrogen.

I2(g) + H2(g) 2HI(g) ∆HO = –9 kJ

Why do some collisions between iodine and hydrogen not result in the formation of the product?

A. The I2 and H2 molecules do not have sufficient energy.

B. The system is in equilibrium.

C. The temperature of the system is too high.

D. The activation energy for this reaction is very low. (Total 1 mark)

17. Equal masses of powdered calcium carbonate were added to separate solutions of hydrochloric acid. The calcium carbonate was in excess. The volume of carbon dioxide produced was measured at regular intervals. Which curves best represent the evolution of carbon dioxide against time for the acid solutions shown in the table below.

25 cm3 of 2 mol dm–3 HCl 50 cm3 of 1 mol dm–3 HCl 25 cm3 of 1 mol dm–3 HCl

A. I III IV

B. I IV III

C. I II III

D. II I III (Total 1 mark)


18. Sodium carbonate and hydrochloric acid react according to the equation below.

Na2CO3(s) + 2HCl(aq) → CO2(g) + 2NaCl(aq) + H2O(l)

Which conditions will produce the fastest initial rate with 2.0 g of powdered sodium carbonate?

A. 100 cm3 of 1.0 mol dm–3 hydrochloric acid at 323 K

B. 50 cm3 of 2.0 mol dm–3 hydrochloric acid at 323 K

C. 100 cm3 of 1.0 mol dm–3 hydrochloric acid at 348 K

D. 50 cm3 of 2.0 mol dm–3 hydrochloric acid at 348 K (Total 1 mark)

19. 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)


20. This question refers to the following reaction.

X2 + 2Y → 2XY

The reaction occurs in a series of steps.

X2 → 2X slow X + Y → XY fast

What is the rate-determining step for this reaction mechanism?

A. X2 + 2Y → 2XY

B. X2 + Y → XY + X

C. X2 → 2X

D. X + Y → XY (Total 1 mark)

21. Consider the following reaction.

2NO(g) + 2H2(g) → N2(g) + 2H2O(g)

A proposed reaction mechanism is:

NO(g) + NO(g) N2O2(g) fast N2O2(g) + H2(g) → N2O(g) + H2O(g) slow N2O(g) + H2(g) → N2(g) + H2O(g) fast

What is the rate expression?

A. rate = k[H2] [NO]2

B. rate = k[N2O2] [H2]

C. rate = k[NO]2 [H2]2

D. rate = k[NO]2 [N2O2]2 [H2] (Total 1 mark)


22. 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)


23. On the axes below sketch two Maxwell-Boltzmann energy distribution curves for the same sample of gas, one at a temperature T and another at a higher temperature T ′ . Label both axes. Explain why raising the temperature increases the rate of a chemical reaction.

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................................................................................................................................................ (Total 5 marks)

24. Factors that affect the rate of a chemical reaction include particle size, concentration of reactants and the temperature of the reaction.

(i) Define the term rate of a chemical reaction.

......................................................................................................................................

...................................................................................................................................... (1)


(ii) List the three characteristic properties of reactant particles which affect the rate of reaction as described by the collision theory.

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...................................................................................................................................... (3)

(Total 4 marks)

25. Consider the following reaction studied at 263 K.

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

It was found that the forward reaction is first order with respect to Cl2 and second order with respect to NO. The reverse reaction is second order with respect to NOCl.

(i) State the rate expression for the forward reaction. (1)

(ii) Predict the effect on the rate of the forward reaction and on the rate constant if the concentration of NO is halved.

(2)

(iii) 1.0 mol of Cl2 and 1.0 mol of NO are mixed in a closed container at constant temperature. Sketch a graph to show how the concentration of NO and NOCl change with time until after equilibrium has been reached. Identify the point on the graph where equilibrium is established.

(4) (Total 7 marks)


26. Hydrogen and nitrogen(II) oxide react according to the following equation.

2H2(g) + 2NO(g) N2(g) + 2H2O(g)

At time = t seconds, the rate of the reaction is

rate = k[H2(g)][NO(g)]2

(i) Explain precisely what the square brackets around nitrogen(II) oxide, [NO(g)], represent in this context.

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...................................................................................................................................... (1)

(ii) Deduce the units for the rate constant k.

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...................................................................................................................................... (1)

(Total 2 marks)


1. B [1]

2. C [1]

3. B [1]

4. B [1]

5. D [1]

6. B [1]

7. D [1]

8. A [1]

9. B [1]

10. B [1]


11. (i) 100 × 4.18 × 35.0; 14630 J / 14600 J / 14.6 kJ; Award [2] for correct final answer. No ECF here if incorrect mass used. 2

(ii) 08.46

78.1 = 0.0386 mol;

0386.06.14 = (–)378 kJ mol–1;

Accept (–)377 and (–)379 kJ mol–1. Award [2] for correct final answer. 2

(iii) heat loss; incomplete combustion; heat absorbed by calorimeter not included; Accept other sensible suggestions. 2 max

[6]

12. (a) all heat is transferred to water/copper sulfate solution / no heat loss; specific heat capacity of zinc is zero/negligible / no heat is absorbed by the zinc; density of water/solution = 1.0 / density of solution = density of water; heat capacity of cup is zero / no heat is absorbed by the cup; specific heat capacity of solution = specific heat capacity of water; temperature uniform throughout solution; Award [1] each for any two. Accept energy instead of heat. 2 max

(b) (i) Tfinal = 73.0 (°C); Allow in the range 72 to 74 (°C).

∆T = 48.2 (°C); Allow in the range 47 to 49 (°C). Award [2] for correct final answer Allow ECF if Tfinal or Tinitial correct. 2

(ii) temperature decreases at uniform rate (when above room temperature) / OWTTE; 1

(iii) 10.1 (kJ); Allow in the range 9.9 to 10.2 (kJ). 1


(c)

×

==1000

0.5000.14CuSOZn nn = 0.0500(mol); 1

(d) –201(kJ mol–1); Allow in the range –197 to –206 (kJ mol–1). Value must be negative to award mark. 1

[8]

13. (i) energy required to break (1 mol of) a bond in a gaseous molecule/state; Accept energy released when (1 mol of) a bond is formed in a gaseous molecule/state / enthalpy change when (1 mol of) bonds are made or broken in the gaseous molecule/state.

average values obtained from a number of similar bonds/compounds / OWTTE; 2

(ii) Bonds broken (1)(C–C) + (1)(O–H) + (5)(C–H) + (1)(C–O) + (3)(O=O) = (1)(347) + (1)(464) + (5)(413) + (1)(358) + (3)(498) = 4728 (kJ); Bonds formed (2 × 2)(C=O) + (3 × 2)(O–H) = (4)(746) + (6)(464) = 5768(kJ); ∆H = 4728 – 5768 = –1040 kJ mol–1 / –1040 kJ; Units needed for last mark. Award [3] for final correct answer. Award [2] for +1040 kJ. 3

(iii) Mr(C2H5OH) = 46.08 / 46.1 and Mr(C8H18) = 114.26/114.3; 1 g ethanol produces 22.57 kJ and 1 g octane produces 47.88 kJ; Accept values ranges of 22.5–23 and 47.8–48 kJ respectively. No penalty for use of Mr = 46 and Mr = 114. 2

[7]

14. (i) lattice enthalpy for a particular ionic compound is defined as ΔH for the process, MX(s) → M+(g) + X–(g);

Accept definition for exothermic process

electron affinity is the energy change that occurs when an electron is added to a gaseous atom or ion; 2


(ii)

Na(s)

+108 kJ mol –1

+

Na(g)

Na (g)+ +

∆H = –411 kJ mol–1

+494 kJ mol –1

Cl (g)1 2 NaCl(s)

+121 kJ mol

–364 kJ mol

Cl(g)

Cl (g)–

f

–1

–1

2

lattice enthalpy = –[(–411) – (+108) – (+494) – (+121) – (–364)] = 770 (kJ mol–1)

Award [2] for all correct formulas in correct positions on cycle diagram. 1 incorrect or missing label award [1]. Award [1] for all correct values in correct positions on cycle diagram.

calculation of lattice enthalpy of NaCl(s) = 770 (kJ mol–1); 4

Allow ECF. Accept alternative method e.g. energy level diagram.

(iii) lattice/network/regular structure; each chloride ion is surrounded by six sodium ions and each sodium ion is surrounded by six chloride ions/6:6 coordination; 2

[8]

15. B [1]

16. A [1]

17. C [1]


18. D [1]

19. C [1]

20. C [1]

21. A [1]

22. B [1]


23.

correctly labelled axes showing number of particles/frequency against (kinetic) energy; correctly shaped graph for T (curve must not touch or cross x axes); T ′ curve to the right of T and with a peak lower than T; increasing the temperature increases the (kinetic) energy of the particles / more particles will possess the necessary activation energy; there will be more collisions per unit time / the frequency of collisions increases / there are more successful collisions; 5

[5]

24. (i) increase in concentration of product per unit time / decrease in concentration of reactant per unit time; 1 Accept change instead of increase/decrease and mass/amount/ volume instead of concentration.

(ii) frequency of collisions; kinetic energy/speed of reactant particles; collision geometry/orientation; 3

[4]

25. (i) rate = k[NO]2 [Cl2]; 1

(ii) rate of reaction will decrease by a factor of 4; no effect on the rate constant; 2


(iii)

y axis labelled concentration/mol dm–3 and x axis is labelled time/s; gradient for [NO]; gradient for [NOCl] will be equal and opposite; equilibrium point identified / two curves level off at same time; 4

[7]

26. (i) the concentration (of nitrogen(II) oxide); 1

Award [0] if reference made to equilibrium.

(ii) mol–2 dm6 s–1 / dm6 mol–2 s–1; 1 Accept (mol–1 dm3)2 s–1.

[2]


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(Total 1 mark) - Chemistry is bae