A first-order heterogenous reaction $A \rightarrow B$ is carried out using a porous spherical catalyst. Assume isothermal conditions, and that intraphase diffusion controls the reaction rate. At a bulk $A$ concentration of $0.3 \mathrm{~mol} \mathrm{~L}^{-1}$, the observed reaction rate in a $3 \mathrm{~mm}$ diameter catalyst particle is $0.2 \mathrm{~mol} \mathrm{~s}^{-1} \mathrm{~L}^{-1}$ catalyst volume. At a bulk $A$ concentration of $0.1 \mathrm{~mol} \mathrm{~L}^{-1}$, the observed reaction rate, in $\mathrm{mol} \mathrm{s}^{-1} \mathrm{~L}^{-1}$ catalyst volume, in a $6 \mathrm{~mm}$ diameter catalyst particle, is
- $0.011$
- $0.033$
- $0.022$
- $0.005$