The standard free energy of activation of a reaction A is 71.5 kJ mol–1 (17.1 kc

Question

The standard free energy of activation of a reaction A is 71.5 kJ mol–1 (17.1 kcal mol–1) at 298 K. Reaction B is one hundred million times faster than reaction A at the same temperature. The products of each reaction are 10.0 kJ mol–1 (2.39 kcal mol–1) more stable than the reactants. (a) What is the standard free energy of activation of reaction B? (b) What is the standard free energy of activation of the reverse of reaction A? (c) What is the standard free energy of activation of the reverse of reaction B?

Explanation / Answer

a)What is the standard free energy of activation of reaction B?

Solution :- Lets first calculate the rate constant for the reaction A

Delta Go = - RT ln k

(71.5 kJ per mol-1*1000 J/1 kJ) = - 8.314 J per mol K * 298 K * ln K

(71.5 kJ per mol-1*1000 J/1 kJ) /( - 8.314 J per mol K * 298 K) = ln K

-28.8589 = ln K

Anti ln(28.8589) = K

2.93*10^-13 = K

Now it says that rate reaction B is 100 million times faster than reaction A at the same temperature

Therefore K for the reaction B = 2.93*10^-13 * 100 million = 2.93*10^-5

Now lets calculate standard free energy of activation for the reaction B

Delta Go = - RT ln K

           = - 8.314 J per mol K * 298 K * 2.93*10^-5

           = 25860 J per mol

Lets convert it to kJ

25860 J per mol * 1 kJ / 1000 J = 25.86 kJ per mol

Therefore the standard free energy of activation for the reaction B is 25.86 kJ /mol

(b) What is the standard free energy of activation of the reverse of reaction A?

Solution :-

When the reaction is reversed then the standard free energy of activation value remains the same but the sign changes

Therefore the standard free energy for the reverse of reaction A is -71.5 kJ/mol

(c) What is the standard free energy of activation of the reverse of reaction B?

Solution :-

When the reaction is reversed then the standard free energy of activation value remains the same but the sign changes

Therefore the standard free energy for the reverse of reaction B is -2586 kJ/mol

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.