Question

Which of the following is/are correct about equilibrium:

• A. Addition of a catalyst does not affect the equilibrium composition of a reaction mixture
• B. $\frac{dlnK}{dT}=\frac{{\Delta }_r{H}^{\circ }}{R{T}^2}$ represents the temperature dependence of the equilibrium constant
• C. If ${\Delta }_{r}G<0$, the reaction is at equilibrium.
• D. Equilibrium constant K is dimensionless

Answer 1

Answer: (A), (B), (D)

The correct options are
A Addition of a catalyst does not affect the equilibrium composition of a reaction mixture
B $\frac{dlnK}{dT}=\frac{{\Delta }_r{H}^{\circ }}{R{T}^2}$ represents the temperature dependence of the equilibrium constant
D Equilibrium constant K is dimensionless

A catalyst increases the rate of forward and reverse reactions that pass through the same transition state and does not affect equilibrium. It lowers the activation energy for the forward and reverse reactions by exactly the same amount.

Equation, $\frac{dlnK}{dT}=\frac{{△}_r{H}^o}{R{T}^2}$ is called as van't Hoff equation and represents the temperature dependence of the equilibrium constant.

${\Delta }_{r}G<0$, for spontaneous reaction
${\Delta }_{r}G>0$, for non spontaneous reaction
${\Delta }_{r}G=0$, for reaction at equilibrium

The equilibrium constant is expressed in terms of activities and because ratios, they are dimensionless numbers. This makes the thermodynamic equilibrium constant dimensionless as well.