R1.1 Measuring enthalpy changes questions for IB Chemistry

122 questions on Measuring enthalpy changes, written by Augment in the style of IB exam papers. Six of them are below in full, to answer on paper.

IB Chemistry
Part of R1 What drives chemical reactions?
SL and HL

Questions by paper and level

SL and HL questions are for students at either level. HL only questions cover what only HL students study.

Paper	SL and HL	HL only	All
Paper 1A	46	2	48
Paper 1B	30	6	36
Paper 2	31	7	38
Every paper	107	15	122

Counted on 10 November 2026

Questions to try

Written by Augment in the style of IB exams, not past papers. Answer them on paper, then check each one against its markscheme with a free account.

Question 1 · CHEM-00115Paper 1A · 1 mark

Which change of state is exothermic?

A
Melting
B
Sublimation
C
Deposition
D
Vaporization

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Question 2 · CHEM-00810Paper 1B · 12 marks

The enthalpy change for the hydration of anhydrous copper(II) sulfate cannot be measured directly.

C u S O_{4} (s) + 5 H_{2} O (l) \to C u S O_{4} \cdot 5 H_{2} O (s) Δ H_{hyd}

A student determined it indirectly from two experiments. In each, the solid was added to 50.0 cm³ of water in a polystyrene cup, stirred, and the highest or lowest temperature was recorded.

Experiment 1: 4.00 g of anhydrous $C u S O_{4}$ dissolved, giving $Δ H_{1}$ .
Experiment 2: 6.25 g of $C u S O_{4} \cdot 5 H_{2} O$ dissolved, giving $Δ H_{2}$ .

	Experiment 1	Experiment 2
Mass of solid / g ± 0.01 g	4.00	6.25
Initial temperature / °C ± 0.1 °C	21.3	21.5
Final temperature / °C ± 0.1 °C	28.7	20.2

Assume the specific heat capacity of the solution is that of water (section 2 of the data booklet) and that only the 50.0 g of water is heated or cooled.

(a)
Suggest why $Δ H_{hyd}$ cannot be measured directly in a calorimeter.
1 mark
(b)
Calculate $Δ H_{1}$ , in kJ mol⁻¹.
3 marks
(c)
Calculate $Δ H_{2}$ , in kJ mol⁻¹.
2 marks
(d)
Construct a Hess's law cycle linking $Δ H_{hyd}$ , $Δ H_{1}$ and $Δ H_{2}$ , and use it to determine $Δ H_{hyd}$ , in kJ mol⁻¹.
2 marks
(e)
The literature value of $Δ H_{hyd}$ is −78.2 kJ mol⁻¹. Calculate the percentage error in the student's value.
1 mark
(f)
Calculate the percentage uncertainty in the temperature change in Experiment 2 and state its effect on the reliability of $Δ H_{hyd}$ .
2 marks
(g)
Suggest one modification to Experiment 2 that would reduce the percentage uncertainty in its temperature change.
1 mark

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Question 3 · CHEM-00701Paper 2 · 6 marks

Saucepans are often made of copper or aluminium, with handles made of a polymer.

Metal	Specific heat capacity / J g⁻¹ K⁻¹
copper	0.385
aluminium	0.897

(a)
Explain why metals are good conductors of heat.
2 marks
(b)
Calculate the energy, in kJ, needed to heat an 850 g copper saucepan from 20.0 °C to 180.0 °C.
2 marks
(c)
An aluminium saucepan of the same mass needs 122 kJ for the same temperature rise. Suggest, with a reason, which saucepan heats up faster on the same cooker.
1 mark
(d)
Suggest why the handles are made of a polymer.
1 mark

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Question 4 · CHEM-00134Paper 1A · 1 mark

Which pair of changes of state are both endothermic?

A
Melting and condensation
B
Freezing and deposition
C
Sublimation and freezing
D
Sublimation and vaporization

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Question 5 · CHEM-00811Paper 1B · 10 marks

The enthalpy change for the reaction $M g (s) + \frac{1}{2} O_{2} (g) \to M g O (s)$ was determined indirectly. A student carried out two experiments, each with 50.0 cm³ of 1.00 mol dm⁻³ hydrochloric acid (an excess) in a polystyrene cup with a lid.

Reaction 1: $M g (s) + 2 H C l (a q) \to M g C l_{2} (a q) + H_{2} (g)$ $Δ H_{1}$
Reaction 2: $M g O (s) + 2 H C l (a q) \to M g C l_{2} (a q) + H_{2} O (l)$ $Δ H_{2}$
Reaction 3: $H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l)$ $Δ H_{3} = - 286 {kJ mol}^{- 1}$

	Reaction 1	Reaction 2
Solid added	Mg ribbon	MgO powder
Mass of solid / g ± 0.001 g	0.240	0.400
Temperature rise / °C ± 0.2 °C	20.6	6.6

(a)
Show that hydrochloric acid is in excess in Reaction 1.
1 mark
(b)
Calculate $Δ H_{1}$ , in kJ mol⁻¹. Assume the solution has the density and specific heat capacity of water.
2 marks
(c)
Calculate $Δ H_{2}$ , in kJ mol⁻¹.
1 mark
(d)
Determine the enthalpy change, in kJ mol⁻¹, for the formation of magnesium oxide from magnesium and oxygen.
2 marks
(e)
The literature value is −602 kJ mol⁻¹. Calculate the percentage error.
1 mark
(f)
Outline why the magnesium ribbon is cleaned with sandpaper before it is weighed, and the effect on $Δ H_{1}$ if this step were left out.
2 marks
(g)
Suggest one source of systematic error, other than heat loss, in Reaction 1.
1 mark

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Question 6 · CHEM-00739Paper 2 · 8 marks

Iron filings and powdered sulfur are mixed. When the mixture is heated at one end, it glows red, the glow spreads through the mixture after the heating has stopped, and a black solid, iron(II) sulfide, forms.

(a)
Classify each of the following as an element, a compound or a mixture: iron; the mixture of iron and sulfur before heating; iron(II) sulfide.
2 marks
(b)
State two differences between the mixture of iron and sulfur and iron(II) sulfide.
2 marks
(c)
Write the equation, including state symbols, for the reaction.
1 mark
(d)
Calculate the mass, in g, of sulfur that reacts exactly with 2.00 g of iron.
2 marks
(e)
State, giving a reason, whether the reaction is exothermic or endothermic.
1 mark

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