Question

If the activation energy for the forward reaction is \( 150 \, \text{kJ/mol} \) and that of the reverse reaction is \( 260 \, \text{kJ/mol} \), what is the enthalpy change for the reaction?

• A. \( 410 \, \text{kJ/mol} \)
• B. \( -110 \, \text{kJ/mol} \)
• C. \( 110 \, \text{kJ/mol} \)
• D. \( -410 \, \text{kJ/mol} \)

Hint:

In exothermic reactions, the activation energy of the reverse reaction is higher than that of the forward reaction, resulting in a negative enthalpy change (\( \Delta H \)).

Answer 1

The Correct Option is B

The enthalpy change \( \Delta H \) for a reaction is given by the difference between the activation energies of the forward reaction (\( E_a^\text{f} \)) and the reverse reaction (\( E_a^\text{r} \)): \[ \Delta H = E_a^\text{f} - E_a^\text{r}. \] Substitute the given activation energies: \[ \Delta H = 150 - 260 = -110 \, \text{kJ/mol}. \] Since \( \Delta H \) is negative, it indicates that the reaction is exothermic, meaning it releases heat. Final Answer: \[ \boxed{-110 \, \text{kJ/mol}} \]