Consider the following equilibrium. $$2X(g) + Y(g) \rightleftharpoons 2Z(g)$$ $\Delta H$ is positive. A catalyst is added to the equilibrium mixture at time $t$. The temperature and volume of the mixture remain constant. Which one of the following graphs best represents the change in the equilibrium ratio $\frac{[Z]}{[X]}$ ?

SSCE VCE Chemistry Rates of Chemical Reactions: Consider the following equilibri

Consider the following equilibrium - VCE - SSCE Chemistry - Question 2 - 2011 - Paper 1

Question 2

Consider the following equilibrium. $$2X(g) + Y(g) \rightleftharpoons 2Z(g)$$ $\Delta H$ is positive. A catalyst is added to the equilibrium mixture at time $t$. ... show full transcript

Worked Solution & Example Answer:Consider the following equilibrium - VCE - SSCE Chemistry - Question 2 - 2011 - Paper 1

Step 1

A catalyst is added to the equilibrium mixture at time $t$

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Answer

When a catalyst is introduced to a reaction at equilibrium, it speeds up both the forward and backward reactions equally but does not change the position of the equilibrium itself. Since the temperature and volume remain constant, the equilibrium constant will stay the same. Therefore, the ratio $\frac{[Z]}{[X]}$ will not change after the addition of the catalyst at time $t$ .

Thus, the graph that represents this behavior is one that shows a horizontal line, indicating that the equilibrium ratio remains constant over time.

Step 2

Which graph best represents the change in $\frac{[Z]}{[X]}$?

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Answer

Based on the analysis, the correct graph is option A, which illustrates a constant ratio for $\frac{[Z]}{[X]}$ after time $t$ , representing that the equilibrium ratio does not change with the addition of a catalyst.

Consider the following equilibrium - VCE - SSCE Chemistry - Question 2 - 2011 - Paper 1

Worked Solution & Example Answer:Consider the following equilibrium - VCE - SSCE Chemistry - Question 2 - 2011 - Paper 1

A catalyst is added to the equilibrium mixture at time $t$

Which graph best represents the change in $\frac{[Z]}{[X]}$?

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