Dinitrogen tetroxide (N2O4) breaks down into nitrogen dioxide (NO2). If the
reaction is reversible and endothermic, which condition will give the largest
yield of NO2?
High temperature and high pressure.
High temperature and low pressure.
Low temperature and high pressure.
Low temperature and low pressure.
The reversible endothermic reaction N₂O₄(g) ⇌ 2NO₂(g) favors the largest yield of nitrogen dioxide (NO₂) under high temperature and low pressure. This condition shifts the equilibrium rightward per Le Chatelier’s principle, as heat drives the endothermic forward reaction and reduced pressure favors more gas moles on the product side.
Reaction Overview
The decomposition increases gas moles from 1 (N₂O₄) to 2 (NO₂), making it endothermic overall. High temperature supplies energy to break N₂O₄ bonds, boosting NO₂ production. Low pressure relieves product-side crowding, further promoting dissociation.
Option Analysis
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High temperature and high pressure: High temperature aids the endothermic shift to NO₂, but high pressure pushes back toward fewer-mole N₂O₄, reducing yield.
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High temperature and low pressure: Ideal combo—temperature favors endothermic direction, low pressure supports mole increase for maximum NO₂.
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Low temperature and high pressure: Worst case; low temperature favors exothermic reverse (N₂O₄ formation), high pressure reinforces fewer moles.
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Low temperature and low pressure: Low temperature hinders endothermic forward reaction despite low pressure helping moles; net low NO₂ yield.
