Concept:To shift a reaction in the backward (reactant) direction, we must manipulate conditions against the thermodynamic and stoichiometric flow of the forward reaction.
Solution:- Temperature: The forward reaction is exothermic (produces heat). Adding heat (increasing temperature) creates an excess on the product side, forcing the equilibrium to shift backward to consume it.
- Pressure: There are 3 moles of gaseous reactants (\( 2\text{NO} + 1\text{O}_2 \)) and only 2 moles of gaseous products (\( 2\text{NO}_2 \)). Decreasing pressure shifts equilibrium toward the side with more moles of gas to restore pressure. This side is the reactant side (left).
- Therefore, combining both Decreasing pressure and increasing temperature effectively forces the reaction backward.
Why other options are incorrect:Decreasing temperature (Options B/C) favors the forward exothermic reaction. Increasing pressure (Option D) favors the forward reaction (fewer moles).
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