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Ch.15 - Chemical Equilibrium

Chapter 15, Problem 1a

(a) Based on the following energy profile, predict whether kf > kr or kf < kr. [Section 15.1]

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hi everyone for this problem. It reads using the energy profile given below identify whether the forward or the reverse reaction is faster. Okay. And we're given the energy as a function of time. One thing we're going to want to reference in order to solve this problem is the Iranians equation which shows the relationship between temperature and the rate constant. Okay. And the Iranians equation is K. Which is the rate constant is equal to a the frequency factor times the the function raised to negative activation energy over R. Which is the universal gas constant and T is temperature. Okay, so when we look at the Iranians equation and we're paying attention to the rate constant, the rate constant decreases with activation energy. And so the relationship is the higher the activation energy, the lower the rate of the reaction. Okay, so let's remember that activation energy is the difference between the threshold energy and the ground state energy of the reactant or product. So let's go ahead and identify activation energy for our forward and reverse reaction for our forward reaction where our reactant are turning into product. This is our activation energy here. Remember activation energy is the threshold, which is the highest point on the curve to the ground state energy of the reactant. Okay, so we're right here that this is our activation energy of the forward and our reverse is going to be when our products turn into reactant. And so our activation energy of the reverse is represented here. This is the highest point of the curve to the ground state energy of the product. So this is the activation energy of the reverse. Okay, you can see here that the reverse reaction has a smaller activation energy, which means it's going to be faster. Okay. And so in terms of which two are faster, the reverse reaction is faster than the forward. So our answer here is the rate of the forward is less than the rate of the reverse. Okay. And this is going to be our final answer, and that is it for this problem. I hope this was helpful.