AP Chemistry
5.11 Catalysis
5.7 Introduction to Reaction Mechanisms
5.6 Reaction Energy Profile
A student investigates the reversible reaction
\[ \text{A(aq)} \rightleftharpoons \text{B(aq)} \]
at \(298\ \text{K}\). The student assigns each catalyzed pathway one of the following labels: homogeneous nonenzymatic, heterogeneous, or enzymatic. The observations and measured activation energies are shown below.
Which statement correctly classifies pathways \(\text{P}\), \(\text{Q}\), and \(\text{R}\) and predicts how each catalyst affects the equilibrium ratio \(\dfrac{[\text{B}]}{[\text{A}]}\) relative to pathway \(\text{U}\)?
\[ \text{A(aq)} \rightleftharpoons \text{B(aq)} \]
at \(298\ \text{K}\). The student assigns each catalyzed pathway one of the following labels: homogeneous nonenzymatic, heterogeneous, or enzymatic. The observations and measured activation energies are shown below.
| Pathway | Observation | \(E_{a,\mathrm{f}}\) \((\text{kJ mol}^{-1})\) | \(E_{a,\mathrm{r}}\) \((\text{kJ mol}^{-1})\) |
|---|---|---|---|
| \(\text{U}\) | No catalyst is present. | \(80\) | \(50\) |
| \(\text{P}\) | \(\text{C(aq)}\) forms \(\text{AC(aq)}\) in an elementary step and is regenerated in a later step. | \(55\) | \(25\) |
| \(\text{Q}\) | \(\text{A(aq)}\) adsorbs onto \(\text{M(s)}\), reacts on its surface, and desorbs as \(\text{B(aq)}\). | \(45\) | \(15\) |
| \(\text{R}\) | A dissolved protein \(\text{E(aq)}\) binds \(\text{A(aq)}\) at a shape-specific active site, releases \(\text{B(aq)}\), and is regenerated. | \(40\) | \(10\) |
Which statement correctly classifies pathways \(\text{P}\), \(\text{Q}\), and \(\text{R}\) and predicts how each catalyst affects the equilibrium ratio \(\dfrac{[\text{B}]}{[\text{A}]}\) relative to pathway \(\text{U}\)?
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