The half-life of a substance in a certain enzyme-catalysed reaction is $138 \; s$. The time required for the concentration of the substance to fall from $1.28 \; mg \; L^{-1}$ to $0.04 \; mg \; L^{-1}$ is ....... $s$.

The reaction $N_{2}O_{5} \longrightarrow 2NO_{2} + \frac{1}{2}O_{2}$ is first order in $N_{2}O_{5}$ having rate constant $6.2 \times 10^{-4} \ s^{-1}$. What is the value of rate of reaction when concentration of $N_{2}O_{5}$ is $1.25 \ mol \ L^{-1}$?

$A$ first order reaction is $50 \%$ complete in $16 \ min$. How much time is required to complete $87.5 \%$ of the reaction (in $min$)?

The integrated rate law equation for a first-order gas-phase reaction $A(g) \rightarrow B(g) + C(g)$ is given by (where $P_i$ is the initial pressure and $P_t$ is the total pressure at time $t$):

If compound $A$ reacts with $B$ following first order kinetics with rate constant $2.011 \times 10^{-3} \ s^{-1}$. The time taken by $A$ (in seconds) to reduce from $7 \ g$ to $2 \ g$ will be $.........$ (Nearest Integer) $[\log 5=0.698, \log 7=0.845, \log 2=0.301]$

If the rate constant is $1.155 \times 10^{-3} \ s^{-1}$,after how many seconds will the concentration of the reactant be reduced to half in a first-order reaction?