CAIE IGCSE Chemistry Exothermic and Endothermic Reactions

Practise classifying energy changes from temperature or profile diagrams and calculating reaction enthalpy by comparing bonds broken with bonds formed.

Exam points

classify an exothermic or endothermic reaction from temperature change or the sign of enthalpy
read activation energy and overall energy change from a labelled reaction profile
calculate enthalpy change as energy to break reactant bonds minus energy released forming bonds

Covered syllabus points

5.1.1—An exothermic reaction transfers 5.1.2—An endothermic reaction takes in 5.1.3—Interpret reaction pathway diagrams 5.1.4—Transfer of thermal energy during a 5.1.5—Activation energy, Ea, as the minimum 5.1.6—And label reaction pathway diagrams 5.1.7—Bond breaking is an endothermic 5.1.8—Enthalpy change of a reaction using

[Maximum number: 1]

When an acid is added to an alkali, the temperature of the reaction mixture rises.
Which words describe this reaction?

decomposition and endothermic

decomposition and exothermic

neutralisation and endothermic

neutralisation and exothermic

[Maximum number: 1]

Which row describes the changes that occur in an endothermic reaction?

energy change

temperature

energy given out to
the surroundings

decreases

energy given out to
the surroundings

increases

energy taken in from
the surroundings

decreases

energy taken in from
the surroundings

increases

[Maximum number: 2]

(a)

The energy level diagram shows the energy profile for the reaction between zinc and dilute sulfuric acid.

Figure for Question (a) — CAIE IGCSE Chemistry

[ 2 ]

(i)

Draw an arrow on the diagram to represent the activation energy.

[ 1 ]

(ii)

Is the reaction endothermic or exothermic? Explain your answer.

[ 1 ]

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Covered syllabus points

5.1 Exothermic and endothermic reactions question 1

5.1 Exothermic and endothermic reactions question 2

5.1 Exothermic and endothermic reactions question 3

Question (a)

Question (i)

Question (ii)