Fig. 1 shows an energy profile drawn for a reversible reaction used to make an organic chemical. Route P is the reaction without a catalyst. Route Q is the ...
Question 1 Report
Fig. 1 shows an energy profile drawn for a reversible reaction used to make an organic chemical. Route P is the reaction without a catalyst. Route Q is the same reaction when a catalyst is used. A student must decide whether adding a catalyst is a useful way to obtain a larger equilibrium yield.
The products have less energy than the reactants.
(a) Which route, P or Q, represents the catalysed reaction? [1]
(b) State the effect of a catalyst on activation energy. [1]
(c) Use Fig. 1 to state whether the forward reaction is exothermic or endothermic. [1]
(d) Explain why a catalyst makes equilibrium reached sooner. [3]
(e) State the effect of adding a catalyst on the position of equilibrium and on the equilibrium yield. [2]
(f) Give one reason why a catalyst is valuable in an industrial reaction even when it does not increase yield. [2]
(g) Name one condition that could change the position of equilibrium for a reaction involving gases. [2]
Answer Details
(a) Route Q is the catalysed route because its peak is lower than route P, showing a lower activation energy. [1]
(b) A catalyst lowers the activation energy. [1]
(c) The forward reaction is exothermic because the products have less energy than the reactants. [1]
(d) A lower activation energy means that more particles have sufficient energy to react when they collide. The forward reaction is therefore faster. The catalyst also speeds up the reverse reaction, so the forward and reverse rates become equal sooner and equilibrium is reached sooner. [3]
(e) A catalyst causes no change in the position of equilibrium and no change in equilibrium yield. It speeds both directions equally rather than favouring one direction. [2]
(f) A catalyst is valuable because it makes the reaction faster. This can allow a lower operating temperature, reducing energy costs, or increase production per hour. [2]
(g) Temperature or pressure can change the position of equilibrium in a reaction involving gases. [2]
Download The App On Google Playstore
Everything you need to excel in your exams
