Question

For a reaction with ${\mathbf{\Delta H}}^{\mathbf{°}}\mathbf{=}\mathbf{40}\mathbf{}\mathbf{kJ}\mathbf{/}\mathbf{mol}$, decide which of the following statements is (are) true. Correct any false statement to make it true. (a) ${\mathbf{\Delta G}}^{\mathbf{°}}$The reaction is exothermic; (b) for the reaction is positive; (c) ${\mathbf{K}}_{\mathbf{eq}}$ is greater than 1; (d) the bonds in the starting materials are stronger than the bonds in the product; and (e) the product is favored at equilibrium.

Short answer

Answer

1. False; The reaction is endothermic.
2. True.
3. False; ${\mathrm{K}}_{\mathrm{eq}}$is less than 1.
4. True.
5. False; The reactant is favored at equilibrium.

Step-by-step solution

Step-by-Step SolutionStep 1: Change in enthalpy (ΔH°) and change in free (ΔG°) energy  

A negative value of ${\mathbf{\Delta H}}^{\mathbf{°}}$for a reaction indicates that the products are favored while a positive value indicates that reactants (i.e., the starting materials) are favored.

Change in enthalpy (ΔH°) and change in free energy (ΔG°) 

${\mathrm{\Delta H}}^{°}$is directly related to ${\mathrm{\Delta G}}^{°}$and hence, the negative value of ${\mathrm{\Delta G}}^{°}$ also indicates that the products are favored.

Assigning true or false

(a) The reaction is exothermic

A positive value of ${\mathrm{\Delta H}}^{°}$corresponds to an endothermic reaction and hence the given statement is false.

The correct statement should be - The reaction is endothermic.

(b) ${\mathrm{\Delta G}}^{°}$ for the reaction is positive

True, since${\mathrm{\Delta H}}^{°}$is directly related to${\mathrm{\Delta G}}^{°}$, a positive value of${\mathrm{\Delta H}}^{°}$corresponds to a positive value of${\mathrm{\Delta G}}^{°}$.

(c) ${\mathrm{K}}_{\mathrm{eq}}$is greater than 1

False, as the positive value of${\mathrm{\Delta H}}^{°}$indicates that the reaction favors the reactants (i.e., the reaction proceeds backward).

The value of ${\mathrm{K}}_{\mathrm{eq}}$ for a backward reaction is always less than 1.

(d) The bonds in the starting materials are stronger than the bonds in the product.

True, Positive value of ${\mathrm{\Delta H}}^{°}$ indicates that the reactants or the starting materials are stronger than the bonds in the product.

(e) The product is favored at equilibrium.

False, the reactants are favored at equilibrium as ${\mathrm{\Delta H}}^{°}$is positive.