Exothermic & Endothermic Reactions Practice Questions

Which two reaction mixtures show exothermic reactions?

Give a reason for your answer.

Calculate the temperature change for reaction mixture B.

Temperature change = .......... °C

Name the type of reaction taking place in mixture A.

Tick (✓) the one process below that is endothermic.

Name one everyday use of an exothermic reaction.

Some sports injury packs contain citric acid and sodium hydrogencarbonate, which react together when the pack is squeezed.

Explain why this reaction is useful in a sports injury pack.

Is the reaction shown in Figure 1 exothermic or endothermic?

Give a reason for your answer.

Which arrow, A or B, shows the activation energy of the reaction?

What is meant by 'activation energy'?

Give the independent variable and the dependent variable in this investigation.

Give one variable the student should control in this investigation.

The highest temperature was reached when 25 cm$^3$ of sodium hydroxide solution had been added.

What does this tell you about the reaction at this point?

Explain why the temperature decreased after 25 cm$^3$ of sodium hydroxide solution had been added.

Use data from the table in your answer.

Describe a method the student could use.

Your method should give valid results.

Suggest two changes the student could make to the apparatus to reduce the energy transferred to the surroundings.

What is meant by an endothermic reaction?

Figure 2 shows part of the reaction profile for the thermal decomposition of calcium carbonate.

Complete Figure 2.

You should:

• complete the profile line
• label the activation energy
• label the overall energy change.

Energy is conserved in chemical reactions.

Compare the energy of the products with the energy of the reactant in this reaction.

Calculate the energy needed to break all the bonds in the reactants.

Energy = .......... kJ/mol

Calculate the energy released when all the bonds in the products are formed.

Energy = .......... kJ/mol

Calculate the overall energy change for this reaction and state whether the reaction is exothermic or endothermic.

Overall energy change = .......... kJ/mol

Draw and label a reaction profile for this reaction on Figure 3.

You should show:

• the relative energies of the reactants and products
• the activation energy
• the overall energy change.

What is meant by an exothermic reaction?

Give one hazard of using hand warmer B.

A hill walker needs a hand warmer for a 5-hour winter walk.

Use the data in the table to explain which hand warmer is more suitable.

The student made two errors when drawing the reaction profile.

Describe the two errors.

Explain, in terms of energy, why the products of an endothermic reaction must have more energy than the reactants.

Calculate the energy needed to break all the bonds in the reactants.

Energy = .......... kJ/mol

Calculate the overall energy change for this reaction.

State whether the reaction is exothermic or endothermic.

Overall energy change = .......... kJ/mol

Calculate the mean temperature rise for the $0.20$ mol dm$^{-3}$ copper sulfate solution.

You should ignore any anomalous result.

Mean temperature rise = .......... °C

Predict the mean temperature rise the student would obtain using $0.30$ mol dm$^{-3}$ copper sulfate solution.

Explain how you worked out your answer.

Predicted temperature rise = .......... °C

Explain why a more concentrated copper sulfate solution gives a greater temperature rise in this investigation.

The soup is at 15 °C before the can is used. It must be served at between 50 °C and 65 °C, within 5 minutes of the button being pressed.

Evaluate which reaction is the most suitable for the company to use in the self-heating can.

Use the information in the table.