answer all questions\n1 multiple choice 2 points\nconsider the three - step mechanism for the reaction of a…

answer all questions\n1 multiple choice 2 points\nconsider the three - step mechanism for the reaction of a through intermediates b and c to produce d shown below.\na→b eₐ = 15 kcal/mol, δh° = 13 kcal/mol\nb→c eₐ = 10 kcal/mol, δh° = - 6 kcal/mol\nc→d eₐ = 2 kcal/mol, δh° = - 20 kcal/mol\nwhich of the three steps is rate - limiting?\nthe reaction of c to d.\nthe reaction of b to c.\nthe reaction of a to b.\nthe most exothermic step is rate - limiting\nall three steps occur at the same rate; there is no rate - limiting step.

answer all questions\n1 multiple choice 2 points\nconsider the three - step mechanism for the reaction of a through intermediates b and c to produce d shown below.\na→b eₐ = 15 kcal/mol, δh° = 13 kcal/mol\nb→c eₐ = 10 kcal/mol, δh° = - 6 kcal/mol\nc→d eₐ = 2 kcal/mol, δh° = - 20 kcal/mol\nwhich of the three steps is rate - limiting?\nthe reaction of c to d.\nthe reaction of b to c.\nthe reaction of a to b.\nthe most exothermic step is rate - limiting\nall three steps occur at the same rate; there is no rate - limiting step.

Answer

Answer:

C. The reaction of A to B.

Explanation:

Step1: Recall rate - limiting step concept

The rate - limiting step of a multi - step reaction is the step with the highest activation energy ($E_a$).

Step2: Compare activation energies

For $A\rightarrow B$, $E_a = 15$ kcal/mol; for $B\rightarrow C$, $E_a=10$ kcal/mol; for $C\rightarrow D$, $E_a = 2$ kcal/mol.

Step3: Determine rate - limiting step

Since 15 kcal/mol (for $A\rightarrow B$) is the highest activation energy among the three steps, the reaction of A to B is the rate - limiting step.