Chemistry 5070 · O Level · Exothermic and endothermic reactions
Exothermic and endothermic reactions — practice question
The balanced equation for the reaction of aluminium with dilute hydrochloric acid is given here. $2Al(s)+6HCl(aq)\rightarrow2AlCl_3(aq)+3H_2(g)$. Fig. 3.1 shows a reaction pathway diagram. Reactants: $2Al(s)+6HCl(aq)$. Products: $2AlCl_3(aq)+3H_2(g)$. The energy changes are marked A and B.
(a(i))[2]
Identify what the energy changes labelled A and B are.
(a(ii))[1]
Use the reaction pathway diagram to explain why energy is released in this reaction.
(b)[1]
Describe a chemical test for hydrogen and the observation if hydrogen is present.
(c)[3]
A sample of aluminium reacts completely with dilute hydrochloric acid. It produces a total of $366\text{ cm}^3$ of hydrogen, measured at r.t.p. Calculate the mass of the sample of aluminium. Give your answer to two significant figures.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “A represents activation energy (Ea)” …