25-minute Test : Part VIII Chemical Reactions and Energy

Which of the combinations about chemical reactions and their enthalpy changes is INCORRECT?

• A

• B

• C

• D

You are given the bond enthalpy data in the diagram. What is the enthalpy change of the following reaction?

H₂(g) + F₂(g) → 2HF(g)

• A. –693 kJ mol⁻¹

• B. +693 kJ mol⁻¹

• C. –1309 kJ mol⁻¹

• D. +1309 kJ mol⁻¹

You are given the thermochemical equations in the diagram. What is the standard enthalpy change for the formation of CaCO₃(s)?

• A. +851 kJ mol⁻¹

• B. –851 kJ mol⁻¹

• C. +1208 kJ mol⁻¹

• D. –1208 kJ mol⁻¹

You are given the data in the diagram. What is the standard enthalpy change for the following reaction?

2NaHCO₃(s) → Na₂CO₃(s) + H₂O(l) + CO₂(g)

• A. +27 kJ mol⁻¹

• B. –27 kJ mol⁻¹

• C. +889 kJ mol⁻¹

• D. –889 kJ mol⁻¹

The change in internal energy and the work done on the surroundings of a reaction are –256 kJ and +35 kJ respectively. What is the heat change of the reaction at constant pressure?

• A. –221 kJ
• B. +221 kJ
• C. –291 kJ
• D. +291 kJ

In a calorimetric experiment, 2.30 g of ethanol (CH₃CH₂OH) was burnt in a spirit burner and it raised the temperature of 300 g of water in a metal container by 35°C. What is the enthalpy change of combustion of ethanol under the experimental conditions?

(Specific heat capacity of water = 4.2 J g⁻¹ K⁻¹ ; relative atomic masses: H = 1.0, C = 12.0, O = 16.0)

• A. –192 kJ mol⁻¹

• B. –383 kJ mol⁻¹

• C. –882 kJ mol⁻¹

• D. –959 kJ mol⁻¹

Given that:

Br₂(g) + 3F₂(g) → 2BrF₃(g)　　ΔH = –511 kJ mol⁻¹

Br₂(g) + 3F₂(g) → 2BrF₃(I)　　 ΔH = –602 kJ mol⁻¹

What is the enthalpy change for the boiling of 1 mole of liquid BrF₃?

• A. –45.5 kJ mol⁻¹

• B. +45.5 kJ mol⁻¹

• C. –91.0 kJ mol⁻¹

• D. +91.0 kJ mol⁻¹

Iron reacts with oxygen in a heat pack according to the following equation:

4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)　　ΔH = –3296 kJ mol⁻¹

How much heat is released when 1.00 g of iron reacts completely?

(Relative atomic mass: Fe = 55.8)

• A. 7.39 kJ

• B. 14.8 kJ

• C. 29.6 kJ

• D. 59.2 kJ

Which of the options in the diagram is INCORRECT?

• A

• B

• C

• D

Consider the enthalpy change cycle. Which of the following expressions shows the correct relationship among the enthalpy changes a, b, c and d?

• A. a + b = c + d

• B. a + c = b + d

• C. b = c – d – a

• D. d = b + c – a