DP IB Chemistry: HL

Topic Questions

Syllabus Edition

First teaching 2014

Last exams 2024

|

5.1 Energetics

11 mark

Which equation below can represent both an enthalpy change of formation and combustion?

  • CH4(g) + 2O2(g)  →  CO2(g) + 2H2O(l)

  • 2Na(s) + ½O2(g)  →  Na2O(s) 

  • HCl(aq) + NaOH(aq)  →  NaCl(aq) + H2O(l)

  • CO(g) + C(s)  →  CO2(g)

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21 mark

A student carried out an experiment to determine the enthalpy change for the combustion of ethanol.

The following results were obtained by the student. The specific heat capacity of water is 4.18 J g−1 K−1.q1_5-1_ib_sl_easy_mcq

start temperature of the water

21 °C

final temperature of the water

41 °C

mass of alcohol burner before burning

259.75 g

mass of alcohol burner after burning

259.18 g

mass of glass beaker plus water

150.00 g

mass of glass beaker

50.0 g

How much of the heat energy produced by the burning of ethanol went into the water?

  • 100 x 4.18 x 20 J 

  • 150 x 4.18 x 20 J

  • 0.57 x 4.18 x 20 J

  • 100 x 4.18 x 41 J

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31 mark

When a sample of ammonium chloride is added to a small beaker of water and stirred, the temperature drops as the ammonium chloride slowly dissolves in the water. 

Which statement about the process is true?

  • The process is endothermic and ΔH is -

  • The process is exothermic and ΔH is -

  • The process is endothermic and ΔH is +

  • The process is exothermic and ΔH is +

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41 mark

Which statement is true about all exothermic reactions?

  • Gases are formed during the reaction

  • They give out heat 

  • The reaction is fast

  • They are combustion reactions

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51 mark

Which processes have a negative enthalpy change? 

  1.  The combustion of an alcohol
  2.  The reaction between hydrochloric acid and sodium hydroxide
  3.  Water vapour condensing
  • I and II only  

  • I and III only  

  • II and III only 

  • I, II and III

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61 mark

The enthalpy change of a chemical reaction can be found using the following relationship: 

q = mcΔT 

In this expression, which of the following is true?

  • m represents the amount of substance in moles

  • The temperature is measured in Centigrade

  • c is the specific heat capacity of the substance

  • The unit of q is kJ

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71 mark

Which is the correct definition for the standard enthalpy of combustion?

  • The enthalpy change when the reactants in a stoichiometric equation react to give the products, under standard conditions

  • The enthalpy change when one mole of a substance is burnt in excess oxygen, under standard conditions

  • The enthalpy change when one mole of water is formed by reacting an acid and an alkali, under standard conditions

  • The enthalpy change when one mole of a product is formed from its elements, under standard conditions

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81 mark

1.20 g of ethanol is combusted releasing 35 500 J of energy. 

What is the molar enthalpy change for the combustion of ethanol?

  • begin mathsize 14px style negative fraction numerator left parenthesis 35500 space cross times space 46.0 right parenthesis over denominator left parenthesis 1.20 space cross times space 1000 right parenthesis end fraction end style

  • begin mathsize 14px style negative fraction numerator left parenthesis 35500 space cross times space 1000 right parenthesis over denominator left parenthesis 1.20 space cross times space 46.0 right parenthesis end fraction end style

  • begin mathsize 14px style fraction numerator left parenthesis 35500 space cross times space 46.0 right parenthesis over denominator left parenthesis 1.20 space cross times space 1000 right parenthesis end fraction end style

  • begin mathsize 14px style fraction numerator left parenthesis 35500 space cross times space 1000 right parenthesis over denominator left parenthesis 1.20 space cross times space 46.0 right parenthesis end fraction end style

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91 mark

Which enthalpy change is described as the enthalpy change when the reactants in a stoichiometric equation react, under standard conditions, to form the products?

  • ΔHӨc

  • ΔHӨneut

  • ΔHӨr

  • ΔHӨf

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101 mark

Which statement describes a closed system?

  • Only matter can be transferred across the boundary

  • Only energy can be transferred across the boundary

  • Energy and matter can be transferred across the boundary

  • Energy and matter cannot be transferred across the boundary

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11 mark

In a calorimetric experiment 2.50 g of a fuel is burnt in oxygen. 30 % of the energy released during the combustion is absorbed by 500 g of water, the temperature of which rises from 25 °C to 68 °C. 

The specific heat capacity of water is 4.2 J g–1 K–1

What is the total energy released per gram of fuel burnt?

  • begin mathsize 14px style fraction numerator 500 space cross times space 4.2 space cross times space left parenthesis 68 space minus space 25 right parenthesis over denominator 2.5 end fraction end style

  • begin mathsize 14px style fraction numerator 500 space cross times space 4.2 space cross times space left parenthesis 273 space plus space left parenthesis 68 space minus space 25 right parenthesis right parenthesis space cross times 100 over denominator 30 space cross times space 2.5 end fraction end style

  • begin mathsize 14px style fraction numerator 500 space cross times space 4.2 space cross times space left parenthesis 68 space minus space 25 right parenthesis space cross times space 100 over denominator 30 space cross times space 2.5 end fraction end style

  • begin mathsize 14px style fraction numerator 500 space cross times space 4.2 space cross times space left parenthesis 68 space minus space 25 right parenthesis space cross times space 100 over denominator 30 end fraction end style

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21 mark

The reaction of hydrochloric acid with sodium hydroxide produced an overall temperature increase of 24.4 K. 

Given the following data, how much thermal energy was evolved during this reaction? 

Initial temperature of 25.0 cm3 hydrochloric acid = 17.6 oC

Initial temperature of 25.0 cm3 sodium hydroxide = 18.5 o

The specific heat capacity of water is 4.18 J g-1 K-1.

  • (25.0 x 4.18 x 6.8) + (25.0 x 4.18 x 5.9)

  • begin mathsize 14px style fraction numerator left parenthesis 25.0 space cross times space 4.18 space cross times space 6.8 right parenthesis space plus space left parenthesis 25.0 space cross times space 4.18 space cross times space 5.9 right parenthesis over denominator 2 end fraction end style

  • 50.0 x 4.18 x begin mathsize 14px style open parentheses fraction numerator 6.8 space plus space 5.9 over denominator 2 end fraction close parentheses end style

  • (50.0 x 4.18 x 6.8) + (50.0 x 4.18 x 5.9)

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31 mark

The temperature rise when 0.1 MJ of heat energy is absorbed by 2.5 kg of solid aluminium is 44.4 oC. 

What is the specific heat capacity of aluminium, in J g-1 K-1?

  • begin mathsize 14px style fraction numerator 100000 over denominator 2.5 space cross times space 44.4 end fraction end style

  • begin mathsize 14px style fraction numerator 100000 over denominator 2500 space cross times space 44.4 end fraction end style

  • begin mathsize 14px style fraction numerator 0.1 over denominator 2.5 space cross times space 44.4 end fraction end style

  • begin mathsize 14px style fraction numerator 0.1 over denominator 2500 space cross times space 44.4 end fraction end style

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41 mark

An iron cube, with a mass of 0.5 kg, increases in temperature by 12.7 K when heated. 

The specific heat capacity of iron is 0.448 J K-1 g-1

What is the enthalpy change, in kJ mol-1, for heating the iron cube?

  • 0.448 x 12.7 x 55.85

  • begin mathsize 14px style fraction numerator 0.448 cross times 12.7 cross times 500 squared over denominator 1000 space cross times space 55.85 end fraction end style

  • begin mathsize 14px style fraction numerator 0.448 space cross times space 12.7 space cross times space 55.85 over denominator 1000 end fraction end style

  • begin mathsize 14px style negative fraction numerator 0.448 space cross times space 12.7 space cross times space 55.85 over denominator 1000 end fraction end style

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51 mark

When completing experiments to measure enthalpy change for exothermic processes, which of the following is not a reason for the experimental data to be lower than the expected value?

  • Heat loss through convection

  • Water vapour released as a product

  • An inadequate supply of oxygen during combustion

  • Heat transfer to the system

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61 mark

Heptathiepane, S7, can undergo complete combustion to form sulfur dioxide. 

S7 (s) + 7O2 (g) → 7SO2 (g) 

Which enthalpy changes can be used to describe this reaction?

 

 

ΔHfθ

ΔHcθ

ΔHr

A

x

B

x

C

x

x

D

x

x

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71 mark

A student obtained the following experimental results for the enthalpy of combustion of cyclohexane (C6H12). 

Mass of water / g

50.00

Initial temperature of the water / °C

19.60

Initial mass of spirit burner and cyclohexane / g

186.79

Final mass of spirit burner and cyclohexane / g

186.29

 

The student determined from this experiment that the enthalpy of combustion of cyclohexane is –1216 kJ mol–1 

The specific heat capacity of water = 4.18 J g–1 K–1
The relative molecular mass (Mr) of cyclohexane = 84.18 

Which calculation will correctly determine the final temperature of the water in this experiment?

  • 19.60 + begin mathsize 14px style fraction numerator 608 over denominator 50.00 space cross times space 4.18 space cross times space 84.18 end fraction end style

  • 19.60 + begin mathsize 14px style fraction numerator 60800 over denominator 5.00 space cross times space 4.18 space cross times space 84.18 end fraction end style

  • 19.60 + begin mathsize 14px style fraction numerator 1216 space cross times space 84.18 over denominator 25.00 space cross times space 4.18 end fraction end style

  • 19.60 + begin mathsize 14px style fraction numerator 1216000 space cross times space 84.18 over denominator 25.00 space cross times space 4.18 end fraction end style

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81 mark

The diagrams below show a simple calorimeter that is commonly used in the school laboratory and the more accurate chamber calorimeter.q8_5-1_ib_sl_hard_mcq

                                               Simple calorimeter

Chamber calorimeter

 

Which of the following statements correctly explain why the chamber calorimeter is more accurate? 

  1. There is less heat loss
  2. There is more complete combustion
  3. There is less fuel lost
  • I and II only 

  • I and III only

  • II and III only 

  • I, II and III

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91 mark

Which of the following assumptions are correct when completing the calorimetry experiment and subsequent calculations for the neutralisation of 25.0 cm3 sulfuric acid by 25.0 cm3 barium hydroxide? 

  1. That both solutions have the same initial temperature
  2. The value of m in q = mcΔT is 50 g
  3. Heat is lost to the surroundings

  • I and II only

  • I and III only

  • II and III only

  • I, II and III

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101 mark

The heat produced by the combustion of magnesium is used to heat some water. 

Which values are needed to calculate the energy transferred during the reaction? 

  1. The mass of magnesium
  2. The mass of the water
  3. The temperature change of the water
  • I and II only

  • I and III only

  • II and III only

  • I, II and III

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11 mark

A student mixed 30.0 cm3 of 0.0250 mol dm-3 potassium hydroxide solution with 30.0 cm3 of 0.0250 mol dm-3 nitric acid. The temperature rose by 0.50 oC. Assume no heat was lost to the surroundings. 

The mixture had a specific heat capacity of 4.18 J g -1 K-1

What is the molar enthalpy change for the reaction?

  • begin mathsize 14px style negative fraction numerator 30 cross times 4.18 cross times 0.5 cross times 1000 over denominator 0.025 cross times 30 end fraction end style

  • negative fraction numerator 60 cross times 4.18 cross times 0.5 space cross times 1000 over denominator 0.025 cross times 30 end fraction

  • begin mathsize 14px style negative fraction numerator 0.025 space cross times space 30 over denominator 60 space space cross times space 4.18 space cross times space 0.5 space space cross times space 1000 end fraction end style

  • begin mathsize 14px style negative fraction numerator 60 space space cross times space 4.18 space cross times space 0.5 over denominator 0.025 space cross times space 30 end fraction end style

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21 mark

An experiment was carried out to determine the approximate value for the molar enthalpy change of neutralisation. 

75 cm3 of 3.00 mol dm–3 hydrochloric acid was placed in a polystyrene beaker of negligible heat capacity. Its temperature was recorded, and then 75 cm3 of
3.00 mol dm−3 potassium hydroxide at the same temperature was quickly added, and the solution stirred. 

The temperature rose by 14 °C. The resulting solution may be considered to have a specific heat capacity of 4.18 J g-1 K-1

Which calculation below is correct?

  • begin mathsize 14px style negative fraction numerator left parenthesis 75 space cross times space 4.18 space cross times space 14 right parenthesis over denominator left parenthesis 6.0 cross times 0.150 right parenthesis end fraction end styleJ mol-1

  • begin mathsize 14px style negative fraction numerator left parenthesis 150 space cross times space 4.18 space cross times space 14 right parenthesis over denominator left parenthesis 3.0 space cross times 0.075 right parenthesis end fraction end styleJ mol-1

  • begin mathsize 14px style negative fraction numerator left parenthesis 150 space cross times space 4.18 space cross times space 14 right parenthesis over denominator left parenthesis 3.0 space cross times 75.0 right parenthesis end fraction end styleJ mol-1

  • begin mathsize 14px style negative fraction numerator left parenthesis 75 space cross times space 4.18 space cross times space 287 right parenthesis over denominator left parenthesis 6.0 cross times space 0.150 right parenthesis end fraction end styleJ mol-1

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31 mark

The table below discusses three types of enthalpy change:

‘+’ means that this type of standard enthalpy change can only have positive values,

‘–’ means that this type of standard enthalpy change can only have negative values,

‘+ / –’ means that either positive or negative values are possible. 

Which row is correct?

 

formation

combustion

neutralisation

A

+

+

+ / –

B

+ / –

+

+ / –

C

+ / –

D

+

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41 mark

Using a spirit burner, ethanol is used to heat a container of water.

In this experiment:

Mass of ethanol burned, g

a

Mass of water, g

b

Specific heat capacity of water, J g–1 K–1

d

Temperature rise, °C

y

 

How much heat energy is absorbed by the water? 

  • ady

  • bdy

  • bd(y+273)

  • (y+273) / ad

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51 mark

An iron block with a mass of 0.11 kg absorbs 504 J of heat energy. What is the temperature rise in K?

Specific heat capacity of iron = 0.448 J g–1 K–1

  • 1.02 x104

  • 1.10

  • 10.23

  • 9.78 x 10-2

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61 mark

Which statements are correct for an endothermic reaction? 

  1. The products are more stable than the reactants
  2. The enthalpy change is positive
  3. The temperature of the surroundings decreases
  • I and II only

  • I and III only

  • II and III only 

  • I, II and III

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71 mark

Which assumptions are correct when calculating the enthalpy change for a reaction in solution? 

  1. The density of the solution is 1 g cm-3
  2. The specific heat capacity of the solution is 4.18 J g-1 K-1
  3. The correct stoichiometric quantities of reactants for a complete reaction are used 

  • I and II only

  • I and III only

  • II and III only

  • I, II and III

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81 mark

What is the closest integer value of the temperature change for this reaction, from the graph

m1

  • 8

  • 9

  • 11

  • 35

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91 mark

Which enthalpy changes correctly describe the following reactions? 

Reaction 1: HNO3 (aq) + NH3 (aq) → NH4NO3 (aq)

Reaction 2: CuCO3 (s) → CuO (s) + CO2 (g)

Reaction 3: S (s) + O2 (g) → SO2 (g)

 

ΔHӨc

ΔHӨf

ΔHӨneut

ΔHӨr

A

2

2

1

3

B

3

2

1

2

C

3

3

1

2

D

2

3

1

3

 

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101 mark

Which systems are correctly described? 

  1. Matter and energy can be transferred across the boundary of an open system
  2. Only matter can be transferred across the boundary of a closed system
  3. Matter and energy cannot be transferred across the boundary of an isolated system
  • I and II only

  • I and III only 

  • II and III only 

  • I, II and III

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