SherpaSherpa Logo

Heat Energy Changes in Chemical Reactions Practice Questions

Question 1

4 marks

A student carried out four experiments, A, B, C and D. In each experiment the temperature of the solution was measured before the change and again at the end of the change.

Experiment Change Initial temperature in °C Final temperature in °C
A ammonium nitrate dissolved in water 21.0 14.5
B dilute hydrochloric acid added to sodium hydroxide solution 20.5 27.8
C magnesium powder added to copper(II) sulfate solution 21.0 35.6
D sodium sulfate solution added to barium chloride solution 20.8 21.9
(a)

Calculate the temperature change in experiment A.

temperature change = .................... °C

(b)

State which experiment is endothermic. Give a reason for your answer.

(c)

In experiment D a white solid forms in the solution.

Name the type of reaction taking place in experiment D.

Question 2

4 marks

The reaction profile in Figure 1 is for the reaction between carbon monoxide and nitrogen dioxide.

15027060reactantsproductsProgress of reactionEnergy in kJ

Figure 1

(a)

State whether this reaction is exothermic or endothermic. Use Figure 1 to give a reason for your answer.

(b)

Use Figure 1 to determine the activation energy for this reaction.

activation energy = .................... kJ

(c)

Use Figure 1 to determine the overall energy change for this reaction.

overall energy change = .................... kJ

Question 3

3 marks
(a)

Explain the term activation energy.

(b)

Complete the two sentences about the energy changes that happen during a chemical reaction.

Breaking bonds in the reactants is ............................. because energy is .............................

Making bonds in the products is ............................. because energy is .............................