Question

Elementary step AH (kJ mol-1) E. (kJ mol-1) A+B > AB 80 100 AB > C -30 40 Ć → P -70 20 *You will need to decide which steps are reversible

Answer the following questions for the reaction sequence A + B --> AB --> C --> P. A table of energy values for this reaction sequence is found above.

1. Draw a diagram of the reaction profile. Label and include all enthalpy changes (delta H) and activation energies for all steps. Draw to scale.

2. Find the activation energy for the overall reaction A + B --> P. Also find the activation energy for the reverse reaction P --> A + B.

3. Find the rate determining step and write the rate law for it. If the rate determining step includes and intermediate, write the detailed steady state approximation (including all rate expressions) for that intermediate.

Answer 1

1) The activation energy is the amount of energy required to activate the reactant molecule.

We plot a graph by taking activation energy in kJ/mol on y - axes and reaction progress on x- axes. ​​​​​​

2) From the graph it's clear that the amount of energy given by A+B to get activated is 100kJ/mol similarly in backward reaction P required an 100kJ/mol of energy tonget activated hence both forward and backward has same amount of activation energy required.

3) Now we see that there are few intermediate formed during the reaction so we eliminate them by using the STEADY STATE APPROXIMATION PRINCIPLE (SSA) so we aplied it on the above elementary reaction as shown below