Which of the following gas-phase reactions exhibits an equilibrium position that remains unaffected by pressure variations?
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Answer: B. N2 + O2 ⇌ 2NO
Explanation
Reactions possessing an equal number of gaseous reactant and product moles show pressure independence. For the reaction of nitrogen and oxygen, two reactant moles produce two nitric oxide product moles. Since net moles do not change, pressure variations cannot shift the chemical equilibrium position. Equilibrium shifts under pressure changes only when a net volume change of gases occurs. The stoichiometric sum of coefficients on both sides of this equation is identically balanced. Thermodynamic equilibrium expressions for this system contain pressure terms that mathematically cancel out.
This principle prevents unnecessary compression costs when operating certain high temperature gas processes. It is a classic textbook illustration of applying Le Chateliers principle to gaseous equilibria. Industrial designers must recognize pressure-neutral reactions to avoid inefficient equipment specifications. Option A has two ozone moles forming three oxygen moles, making its equilibrium pressure sensitive. Option C features two reactant moles forming one product mole, showing strong pressure dependence. Option D has three reactant moles forming two product moles, so pressure strongly affects its yield.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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