CIE iGCSE Co-Ordinated Science C5.1 Exothermic and endothermic reactions Exam Style Questions Paper 4
Question
Ammonia is made from the reaction of nitrogen and hydrogen in the Haber process.
N2 + 3H2 2NH3
(a) State the sources of the nitrogen and hydrogen used in the Haber process.
nitrogen …………………………………………………………………………………………………………………….
hydrogen …………………………………………………………………………………………………………………..
(b) Fig. 5.1 shows the energy level diagram for the reaction between nitrogen and hydrogen.
(i) Draw an arrow on Fig. 5.1 to show the energy change in the reaction.
Label your arrow A.
(ii) Draw an arrow on Fig. 5.1 to show the activation energy of the reaction.
Label your arrow B.
(iii) Explain if Fig. 5.1 represents an exothermic or endothermic reaction.
Use ideas about bond breaking and bond making in your answer.
(c) 58.8kg of nitrogen gas reacts with hydrogen gas to make 142.8kg of ammonia gas.
N2 + 3H2 2NH3
Calculate the volume occupied by 142.8kg of ammonia gas.
The volume of one mole of any gas is 24dm3 at room temperature and pressure (r.t.p.).
volume of ammonia gas = ………………………………………….. dm3
▶️Answer/Explanation
Ans : 5(a) nitrogen – (from the) air ;
hydrogen – from the reaction of methane / natural gas with steam ;
5(b)(i)
5(b)(ii)
5(b)(iii) (exothermic because)
energy change is negative / energy is given out in the reaction / energy of reactants is higher than energy of products ;
bond breaking is endothermic / owtte ;
bond making is exothermic / owtte ;
more energy is given out (in bond making) than is taken in (in bond breaking) ;
5(c) Mr of NH3 = 17 ;
moles of NH3 = 142 800 ÷ 17 = 8400 ;
volume of NH3 = 8400 ×24 = 201 600 (dm3) ;