In a first-order reaction, the initial concentration of $A$ is $0.5 \mathrm{~mol} \mathrm{~L}^{-1}$. After 20 minutes, the concentration reduces to $0.4 \mathrm{~mol} \mathrm{~L}^{-1}$. The rate constant is (in $\mathrm{min}^{-1}$ ).

The activation energy for a reaction is $9.0 \mathrm{~K} \mathrm{cal} \mathrm{mol}^{-1}$. The increase in the rate constant when its temperature is increased from 298 K to 308 K is

$A(g) \longrightarrow B(g)$ is a first order reaction. The initial concentration of $A$ is $0.2 \mathrm{~mol} \mathrm{~L}^{-1}$. After 10 minutes the concentration of $B$ is found to be $0.18 \mathrm{~mol} \mathrm{~L}^{-1}$. The rate constant (in $\min ^{-1}$ ) for the reaction is

Which is correct about zero order reaction?