10-minute Quiz : Chapter 33 Energy changes in chemical reactions

Which of the following statements concerning energy are correct?

(1) Energy cannot be created or destroyed.

(2) Energy can be changed from one form into another.

(3) The total amount of energy of the system and its surroundings before and after a reaction remains constant.

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)

Which of the following statements concerning the reaction of water with quicklime are correct?

(1) Ionic bonds are broken in the reaction.

(2) Covalent bonds are broken in the reaction.

(3) The ΔH of the reaction has a positive value.

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)

Which of the following processes are endothermic?

(1) H₂ → 2H

(2) HCl → H + Cl

(3) 2H + O → H₂O

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)

Consider the enthalpy level diagram of a reaction as shown. Which of the combinations is correct?

• A
• B
• C
• D

Consider the following equation.

Mg(s) + CuSO₄(aq) → MgSO₄(aq) + Cu(s)　　ΔH < 0

Which of the following statements concerning the reaction are correct?

(1) This is a displacement reaction.

(2) This is a redox reaction.

(3) This is an exothermic reaction.

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)

The enthalpy change of combustion of methane is −890.8 kJ mol⁻¹. Which of the following statements is/are correct?

(1) The combustion of methane releases heat.

(2) The combustion of methane absorbs heat.

(3) The total enthalpy of the products of the combustion of methane is less than that of methane and oxygen.

• A. (1) only
• B. (2) only
• C. (1) and (3) only
• D. (2) and (3) only

A pair of solution is mixed under room conditions. The graph shows the variation of the temperature of the mixture with time. Which of the following may the pair of solution be?

(1) Fe(NO₃)₂(aq) and NaOH(aq)

(2) NH₃(aq) and HNO₃(aq)

(3) AgNO₃(aq) and HCl(aq)

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)

When a reaction is carried out at constant pressure,

• A. the reaction is likely to be endothermic.
• B. the reaction is likely to be exothermic.
• C. the heat change is equal to the enthalpy change.
• D. the heat change is equal to the change in internal energy.

Which of the following statements concerning an exothermic reaction is correct?

• A. The temperatures of the system and the surroundings both increase.
• B. The energy released during bond-forming is greater than that absorbed during bond-breaking.
• C. It does not involve any bond-breaking processes.
• D. It does not absorb any energy from the surroundings during the course of the reaction.

Chlorine and ethane react to produce chloroethane and hydrogen chloride. The equation for the reaction is shown below.

C₂H₆ + Cl₂ → C₂H₅Cl + HCl

You are given the bond enthalpy data as shown. What is the enthalpy change of the reaction between chlorine and ethane?

• A. −1020 kJ mol⁻¹
• B. −120 kJ mol⁻¹
• C. +1020 kJ mol⁻¹
• D. +120 kJ mol⁻¹