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R1.2 Energy cycles in reactions - IB Questionbank | RevisionDojo

Practice R1.2 Energy cycles in reactions with authentic IB Chemistry exam questions for both SL and HL students. This question bank mirrors Paper 1A, 1B, 2 structure, covering key topics like atomic structure, chemical reactions, and organic chemistry. Get instant solutions, detailed explanations, and build exam confidence with questions in the style of IB examiners.

Paper

Level

Question 1

HLPaper 1A

Which of the following best describes the enthalpy change when 1 mol of substance is completely burned in oxygen under standard conditions?

Question 2

HLPaper 2

Born–Haber cycles are used to calculate lattice enthalpy of ${NaCl}$ . Given:

$\Delta H^\circ_\mathrm{f} = -411\ \mathrm{kJ\ mol^{-1}}$
Sublimation of Na: $+108$
Ionization energy Na: $+496$
Bond enthalpy ${Cl_2}$ : $+243$
Electron affinity Cl: $-349$

State what is meant by lattice enthalpy.

[1]

Describe the steps of a Born–Haber cycle for ${NaCl}$ .

[2]

Calculate the lattice enthalpy.

[3]

Question 3

SLPaper 2

When ethane ( $\text{C}_2\text{H}_6$ ) reacts with chlorine gas under UV light, a substitution reaction occurs. This involves breaking the $\text{Cl}-\text{Cl}$ bond to form free radicals before new bonds are made.

Identify the bond being broken in chlorine gas.

[1]

State whether breaking this bond is endothermic or exothermic and justify your answer.

[2]

Define the term bond enthalpy.

[2]

Suggest why ultraviolet light is needed to start this reaction.

[1]

State the bond formed between the carbon atom and the incoming chlorine atom during the substitution.

[1]

Question 4

SLPaper 1A

What is the heat change, in kJ, when $100.0 \text{ g}$ of aluminium is heated from $19.0^\circ\text{C}$ to $32.0^\circ\text{C}$ ?

Specific heat capacity of aluminium: $0.90 \text{ J g}^{-1} \text{K}^{-1}$

Question 5

HLPaper 1A

What is the primary reason why values calculated using average bond enthalpies often differ from those calculated using standard enthalpy changes of reaction?

[1]

Question 6

HLPaper 1A

Which reaction corresponds to $\Delta H^\circ_{\text{f}}$ of water?

Question 7

HLPaper 1A

A reaction has $\Delta H^\ominus = -200\ \text{kJ}\,\text{mol}^{-1}$ . The sum of the standard enthalpies of formation of the products is $-650\ \text{kJ}\,\text{mol}^{-1}$ . What is the sum of the standard enthalpies of formation of the reactants?

Question 8

SLPaper 2

Methane ( $\text{CH}_4$ ) is a common fuel used in domestic gas stoves. Combustion involves the breaking and forming of covalent bonds.

State what is meant by the term average bond enthalpy.

[1]

Identify one reason why average bond enthalpy values differ from experimentally determined $\Delta H$ values.

[1]

State whether bond breaking is endothermic or exothermic and justify your answer.

[2]

Methane has four $\text{C}-\text{H}$ bonds. Estimate the total energy required to break all $\text{C}-\text{H}$ bonds in one mole of methane using the average bond enthalpy for $\text{C}-\text{H} = 412\ \text{kJ mol}^{-1}$ .

[1]

Explain why combustion of methane is an exothermic process, using bond enthalpy ideas.

[2]

Question 9

HLPaper 1A

Using average bond enthalpies:

$E(\text{H--H}) = 436\text{ kJ mol}^{-1}$
$E(\text{Cl--Cl}) = 242\text{ kJ mol}^{-1}$
$E(\text{H--Cl}) = 431\text{ kJ mol}^{-1}$

Estimate the enthalpy change, $\Delta H^\ominus$ , for the reaction: $\text{H}_2(\text{g}) + \text{Cl}_2(\text{g}) \rightarrow 2\text{HCl}(\text{g})$

Question 10

SLPaper 1A

What is the enthalpy change, in J, when 5 g of liquid is heated from 10°C to 18°C?

Specific heat capacity of liquid: 4.18 $kJ \, kg^{−1} \, K^{−1}$

Paper

Level

Question 1

HLPaper 1A

Which of the following best describes the enthalpy change when 1 mol of substance is completely burned in oxygen under standard conditions?

Question 2

HLPaper 2

Born–Haber cycles are used to calculate lattice enthalpy of ${NaCl}$ . Given:

$\Delta H^\circ_\mathrm{f} = -411\ \mathrm{kJ\ mol^{-1}}$
Sublimation of Na: $+108$
Ionization energy Na: $+496$
Bond enthalpy ${Cl_2}$ : $+243$
Electron affinity Cl: $-349$

State what is meant by lattice enthalpy.

[1]

Describe the steps of a Born–Haber cycle for ${NaCl}$ .

[2]

Calculate the lattice enthalpy.

[3]

Question 3

SLPaper 2

Identify the bond being broken in chlorine gas.

[1]

State whether breaking this bond is endothermic or exothermic and justify your answer.

[2]

Define the term bond enthalpy.

[2]

Suggest why ultraviolet light is needed to start this reaction.

[1]

State the bond formed between the carbon atom and the incoming chlorine atom during the substitution.

[1]

Question 4

SLPaper 1A

What is the heat change, in kJ, when $100.0 \text{ g}$ of aluminium is heated from $19.0^\circ\text{C}$ to $32.0^\circ\text{C}$ ?

Specific heat capacity of aluminium: $0.90 \text{ J g}^{-1} \text{K}^{-1}$

Question 5

HLPaper 1A

What is the primary reason why values calculated using average bond enthalpies often differ from those calculated using standard enthalpy changes of reaction?

[1]

Question 6

HLPaper 1A

Which reaction corresponds to $\Delta H^\circ_{\text{f}}$ of water?

Question 7

HLPaper 1A

Question 8

SLPaper 2

Methane ( $\text{CH}_4$ ) is a common fuel used in domestic gas stoves. Combustion involves the breaking and forming of covalent bonds.

State what is meant by the term average bond enthalpy.

[1]

Identify one reason why average bond enthalpy values differ from experimentally determined $\Delta H$ values.

[1]

State whether bond breaking is endothermic or exothermic and justify your answer.

[2]

[1]

Explain why combustion of methane is an exothermic process, using bond enthalpy ideas.

[2]

Question 9

HLPaper 1A

Using average bond enthalpies:

$E(\text{H--H}) = 436\text{ kJ mol}^{-1}$
$E(\text{Cl--Cl}) = 242\text{ kJ mol}^{-1}$
$E(\text{H--Cl}) = 431\text{ kJ mol}^{-1}$

Estimate the enthalpy change, $\Delta H^\ominus$ , for the reaction: $\text{H}_2(\text{g}) + \text{Cl}_2(\text{g}) \rightarrow 2\text{HCl}(\text{g})$

Question 10

SLPaper 1A

What is the enthalpy change, in J, when 5 g of liquid is heated from 10°C to 18°C?

Specific heat capacity of liquid: 4.18 $kJ \, kg^{−1} \, K^{−1}$

Paper

Level

Question 1

HLPaper 1A

Which of the following best describes the enthalpy change when 1 mol of substance is completely burned in oxygen under standard conditions?

Question 2

HLPaper 2

Born–Haber cycles are used to calculate lattice enthalpy of ${NaCl}$ . Given:

$\Delta H^\circ_\mathrm{f} = -411\ \mathrm{kJ\ mol^{-1}}$
Sublimation of Na: $+108$
Ionization energy Na: $+496$
Bond enthalpy ${Cl_2}$ : $+243$
Electron affinity Cl: $-349$

State what is meant by lattice enthalpy.

[1]

Describe the steps of a Born–Haber cycle for ${NaCl}$ .

[2]

Calculate the lattice enthalpy.

[3]

Question 3

SLPaper 2

Identify the bond being broken in chlorine gas.

[1]

State whether breaking this bond is endothermic or exothermic and justify your answer.

[2]

Define the term bond enthalpy.

[2]

Suggest why ultraviolet light is needed to start this reaction.

[1]

State the bond formed between the carbon atom and the incoming chlorine atom during the substitution.

[1]

Question 4

SLPaper 1A

What is the heat change, in kJ, when $100.0 \text{ g}$ of aluminium is heated from $19.0^\circ\text{C}$ to $32.0^\circ\text{C}$ ?

Specific heat capacity of aluminium: $0.90 \text{ J g}^{-1} \text{K}^{-1}$

Question 5

HLPaper 1A

What is the primary reason why values calculated using average bond enthalpies often differ from those calculated using standard enthalpy changes of reaction?

[1]

Question 6

HLPaper 1A

Which reaction corresponds to $\Delta H^\circ_{\text{f}}$ of water?

Question 7

HLPaper 1A

Question 8

SLPaper 2

Methane ( $\text{CH}_4$ ) is a common fuel used in domestic gas stoves. Combustion involves the breaking and forming of covalent bonds.

State what is meant by the term average bond enthalpy.

[1]

Identify one reason why average bond enthalpy values differ from experimentally determined $\Delta H$ values.

[1]

State whether bond breaking is endothermic or exothermic and justify your answer.

[2]

[1]

Explain why combustion of methane is an exothermic process, using bond enthalpy ideas.

[2]

Question 9

HLPaper 1A

Using average bond enthalpies:

$E(\text{H--H}) = 436\text{ kJ mol}^{-1}$
$E(\text{Cl--Cl}) = 242\text{ kJ mol}^{-1}$
$E(\text{H--Cl}) = 431\text{ kJ mol}^{-1}$

Estimate the enthalpy change, $\Delta H^\ominus$ , for the reaction: $\text{H}_2(\text{g}) + \text{Cl}_2(\text{g}) \rightarrow 2\text{HCl}(\text{g})$

Question 10

SLPaper 1A

What is the enthalpy change, in J, when 5 g of liquid is heated from 10°C to 18°C?

Specific heat capacity of liquid: 4.18 $kJ \, kg^{−1} \, K^{−1}$

R1.2 Energy cycles in reactions Questionbank