For the exothermic reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), which of the following changes will increase the yield of SO3 at equilibrium?
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Correct answer
B. Decreasing the temperature
Principle or equation
Le Chatelier's principle: for an exothermic reaction, decreasing temperature shifts equilibrium toward products. Also, decreasing volume shifts toward fewer gas moles, but here increasing volume would shift left.
Why this answer is correct
The reaction has 3 moles of gas on the left and 2 on the right. Decreasing volume (not increasing) would favor products. Decreasing temperature favors the exothermic forward reaction. A catalyst does not shift equilibrium. Removing SO2 would shift left.
Example
If the reaction is at equilibrium and the temperature is lowered, the system will produce more SO3 to release heat.
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