Energy is conserved in chemical reactions. What is meant by the term ‘conservation of energy’?

• energy is created in chemical reactions

• energy is used up in chemical reactions

• no energy is transferred in a chemical reaction

• the amount of energy in the universe at the end of a chemical reaction is the same as before the reaction takes place

A student carried out an investigation into the temperature change when citric acid reacts with sodium hydrogen carbonate. The student’s results are shown in Table 1. What type of reaction takes place between citric acid and sodium hydrogen carbonate?

• endothermic

• exothermic

• isothermic

• thermal decomposition

Which of the following is an example of an exothermic reaction?

• combustion

• cooking an egg

• photosynthesis

• thermal decomposition

Which variable would not affect the temperature change in a reaction between a metal carbonate and an acid?

• the volume of acid

• the concentration of the acid

• the mass of metal carbonate

• the room temperature

In an investigation into the temperature change during a chemical reaction, how can the transfer of energy to the surrounding air be minimised?

• carry out the reaction in a glass beaker

• carry out the reaction in a polystyrene cup

• use a higher concentration of reactants

• use a thermometer with a higher resolution

A group of students carried out an investigation into the reaction between sodium hydroxide and hydrochloric acid. The students’ results are shown in Table 2.

What is the mean temperature change to 2 significant figures?

• 11°C

• 12°C

• 13°C

• 47°C

What is activation energy?

• the energy that the reactant particles have at the start of a reaction

• the energy that is released in a chemical reaction

• the energy needed to get particles moving

• the energy needed for a reaction to occur

Figure 1 shows a reaction profile for an exothermic chemical reaction. Which label in Figure 1 represents the activation energy?

• W

• X

• Y

• Z

Figure 1 shows a reaction profile for an exothermic chemical reaction. Which label in Figure 1 represents the energy of the reactants?

• W

• X

• Y

• Z

Figure 1 shows a reaction profile for an exothermic chemical reaction. Which label in Figure 1 represents the overall energy change of the reaction?

• W

• X

• Y

• Z