Chapter 3: Rate Laws


Deriving -rA:

The forward rate is:

\( r'_{A_{\text{for}}} = \frac{-k_A P_A P_B}{1 + K_A P_A} \)

And the reverse rate law is:

\( r'_{A_{\text{rev}}} = \frac{k_{-A} P_C}{1 + K_A P_A} \)

The net rate for species A is the sum of the forward and reverse rate laws:

\( r_A = r_{A_{\text{net}}} = r_{A_{\text{for}}} + r_{A_{\text{rev}}} \)

Substituting for rfor and rrev:

\( r_A = \frac{-k_A P_A P_B}{1 + K_A P_A} + \frac{k_{-A} P_C}{1 + K_A P_A} \)

\( -r_A = \frac{k_A P_A P_B}{1 + K_A P_A} - \frac{k_{-A} P_C}{1 + K_A P_A} = \frac{k_A P_A P_B - k_{-A} P_C}{1 + K_A P_A} \)

\( K_P = \frac{P_{C_e}}{P_{A_e} P_{B_e}} = \frac{k_A}{k_{-A}} \)

\( -r'_{A} = \frac{k_A}{1 + K_A P_A} \left( P_A P_B - \frac{P_C}{K_P} \right) \)



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