This question asks about the characteristics of a chemical equilibrium in a reversible reaction. Understanding the dynamic nature of equilibrium is key to answering this question.
Correct Option: A) The rates of the forward and backward reactions become equal and the concentrations of reactants and products become constant. This statement accurately describes the two essential conditions for chemical equilibrium: equal rates of opposing reactions and constant concentrations of all species.
The question asks for the best description of chemical equilibrium in a closed vessel. We need to recall the fundamental characteristics of a chemical equilibrium, especially its dynamic nature.
Correct Option: B) Dynamic in nature, since both forward and reverse reactions continue to occur at equal rates
This option accurately describes chemical equilibrium. At equilibrium, the forward reaction (reactants to products) and the reverse reaction (products to reactants) proceed simultaneously at the same rate. This results in no net change in the concentrations of reactants and products, even though individual molecules are constantly reacting.
The question asks about the Law of Mass Action, a fundamental principle in chemical kinetics. We need to identify the correct statement that defines this law, specifically how it relates the rate of a chemical reaction to the concentrations of reactants.
The equilibrium constant (\(K_c\)) for a reversible reaction is defined by the ratio of the product of the concentrations of products to the product of the concentrations of reactants, with each concentration raised to the power of its stoichiometric coefficient in the balanced chemical equation.
Correct Option: D) \(K_c = [C]^c[D]^d / [A]^a[B]^b\). This option correctly represents the equilibrium constant expression according to the law of mass action.
This question tests the fundamental relationship between the equilibrium constant of a forward reaction and its reverse reaction. We need to recall how the expression for the equilibrium constant changes when a reaction is reversed.
Consider a general reversible reaction:
\[ aA + bB \rightleftharpoons cC + dD \]
The equilibrium constant, \(K_c\), for this forward reaction is given by the expression:
\[ K_c = \frac{[C]^c [D]^d}{[A]^a [B]^b} \]
Now, consider the reverse reaction:
\[ cC + dD \rightleftharpoons aA + bB \]
The equilibrium constant for this reverse reaction, \(K_c'\), is given by:
\[ K_c' = \frac{[A]^a [B]^b}{[C]^c [D]^d} \]
By comparing the expressions for \(K_c\) and \(K_c'\), we can see that \(K_c'\) is the reciprocal of \(K_c\):
\[ K_c' = \frac{1}{\frac{[C]^c [D]^d}{[A]^a [B]^b}} = \frac{1}{K_c} \]
Rearranging this relationship, we get:
\[ K_c = \frac{1}{K_c'} \]
Correct Option: A) Kc = 1/Kc'
The equilibrium constant (\(K_c\)) for a reversible reaction is a ratio of product concentrations to reactant concentrations, each raised to the power of their stoichiometric coefficients. When the stoichiometric coefficients of a balanced chemical equation are multiplied by a factor, the new equilibrium constant is related to the original constant by raising the original constant to the power of that factor.
Consider a general reversible reaction:
\[ aA + bB ightleftharpoons cC + dD \]The equilibrium constant (\(K_c\)) for this reaction is given by:
\[ K_c = \frac{[C]^c [D]^d}{[A]^a [B]^b} \]Now, if the entire equation is doubled (multiplied by 2), the new reaction becomes:
\[ 2aA + 2bB ightleftharpoons 2cC + 2dD \]The new equilibrium constant (\(K'\)) for this doubled reaction will be:
\[ K' = \frac{[C]^{2c} [D]^{2d}}{[A]^{2a} [B]^{2b}} \]This can be rewritten as:
\[ K' = \left( \frac{[C]^c [D]^d}{[A]^a [B]^b} \right)^2 \]By comparing this with the original \(K_c\) expression, we can see that:
\[ K' = (K_c)^2 \]B) K' = (Kc)^2. As derived, when the stoichiometric coefficients of a reaction are doubled, the new equilibrium constant is the square of the original equilibrium constant.