Unit-9 Chemical Equilibrium
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Unit-9 Chemical Equilibrium
Answer: In a reversible reaction both forward and reverse reactions take place; the Haber process (N2 + 3H2 ⇌ 2NH3) is a classic example.
Answer: Guldberg and Waage proposed the law of mass action which states that the rate of a reaction is proportional to the product of the active masses of the reactants.
Answer: In dynamic equilibrium the forward and reverse reactions proceed at equal rates, so no net change occurs in concentrations.
Answer: Kc = [products]^coefficient / [reactants]^coefficient, giving [NH3]^2 divided by [N2] times [H2]^3.
Answer: Increasing temperature favours the endothermic direction, which is the reverse reaction here, so the equilibrium shifts towards the reactants.
Answer: Combustion reactions such as burning magnesium go to completion and cannot be reversed easily, so they are irreversible.
Answer: Kc changes only with temperature; it is independent of concentration, pressure, catalyst and initial amounts.
Answer: A catalyst speeds up both forward and reverse reactions equally, so the equilibrium position remains unchanged.
Answer: Pressure change has no effect when the number of moles of gaseous reactants equals the number of moles of gaseous products (2 = 2 here).
Answer: According to Le Chatelier's principle, increasing a product concentration shifts the equilibrium towards the reactants to reduce the added amount.
Answer: At equilibrium the forward and reverse reaction rates are equal and the concentrations of reactants and products become constant.
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Answer: Increasing reactant concentration shifts the equilibrium towards the products to consume the added reactant, according to Le Chatelier's principle.
Answer: A closed system is necessary so that neither reactants nor products can escape and equilibrium can be established.
Answer: A large Kc means the concentration of products is much greater than that of reactants, so products are favoured.
Answer: Increasing temperature favours the endothermic (heat-absorbing) direction, which for an endothermic reaction is the forward direction.
Answer: The Haber process combines nitrogen and hydrogen to produce ammonia: N2 + 3H2 ⇌ 2NH3.
Answer: According to Le Chatelier's principle, increasing pressure favours the side with fewer gas molecules to reduce pressure.
Answer: Neutralization of a strong acid and base goes essentially to completion, so it is treated as an irreversible reaction.
Answer: Equilibrium is dynamic and can be reached by starting either with reactants alone or with products alone.
Answer: Pure solids and pure liquids have constant active mass and are not included in the Kc expression, so only CO2 appears.