Question

The reaction, $X + 2Y + Z \to N$ occurs by the following mechanism
(i) $X + Y \rightleftharpoons M$ (very rapid equilibrium)
(ii) $M + Z \to O$ (slow)
(iii) $O + Y \to N$ (very fast)
What is the rate law for this reaction?

• A. Rate $= k\left[Z\right]$
• B. Rate $= k\left[X\right]\left[Y\right]^{2}\left[Z\right]$
• C. Rate $= k\left[N\right]$
• D. Rate $= k\left[X\right]\left[Y\right]\left[Z\right]$

Answer 1

Answer: (D)

$K_{C} =\frac{\left[M\right]}{\left[X\right]\left[Y\right]} \Rightarrow \left[M\right] = K_{C} \left[X\right]\left[Y\right]$
Rate $= K'\left[M\right]\left[Z\right] =K' K_{c} \left[X\right]\left[Y\right]\left[Z\right]$
$ = K\left[X\right]\left[Y\right]\left[Z\right]$