A chemical reaction reactants ⇌ productsis shifted towards the products both by increase of pressure and rise in temperature then the forward reaction is
Correct answer: D. endothermic with ∆ n negative
- A. endothermic with ∆n positive
- B. exothermic with ∆ n negative
- C. exothermic with ∆ n positive
- D. endothermic with ∆ n negative
Explanation
According to Le Châtelier's principle, if a system at equilibrium is subjected to stress, the system will shift its equilibrium position in a way that tends to relieve the stress. Increasing the pressure on a system at equilibrium will shift the equilibrium towards the side of the reaction with a fewer number of moles of gas. This is because increasing the pressure favors the reaction that reduces the overall volume of the system. Increasing the temperature of a system at equilibrium will shift the equilibrium towards the endothermic reaction. This is because increasing the temperature provides energy to the system, which favors the reaction that absorbs energy. Therefore, if a chemical reaction is shifted towards the products both by an increase in pressure and a rise in temperature, then the forward reaction must be endothermic and have a smaller number of moles of gas on the product side. This means that the correct answer is (D), endothermic with Δn negative.
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About Chemical Equilibrium
Reversible reactions reach dynamic equilibrium when forward and reverse rates become equal, and Le Chatelier's principle predicts the effect of changing concentration, pressure or temperature. The chapter also covers solubility product, the common ion effect, buffer action and the conditions used in Haber's process, with equilibrium shifts distinguished from changes in the equilibrium constant.
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