Question

The yield of the product in the reaction
\[ A_2(g) + 2B(g) \rightleftharpoons C(g) + Q\,kJ \] would be higher at

• A. high temperature and high pressure
• B. high temperature and low pressure
• C. low temperature and high pressure
• D. low temperature and low pressure

Hint:

Exothermic reaction: low temperature favours products. If gaseous moles decrease, high pressure favours products.

Answer 1

The Correct Option is C

Step 1: Analyze effect of temperature (Le Chatelier principle).
Reaction gives \(+Q\,kJ\) on product side, so reaction is exothermic.
For exothermic reactions, lowering temperature shifts equilibrium towards products.
Step 2: Analyze effect of pressure.
Reactant moles of gas:
\[ 1 + 2 = 3 \] Product moles of gas:
\[ 1 \] Since products have fewer moles, increasing pressure shifts equilibrium towards products.
Step 3: Combine both effects.
To maximize product yield:
- low temperature (favours exothermic direction)
- high pressure (favours fewer moles side)
Final Answer: \[ \boxed{\text{low temperature and high pressure}} \]