For a first order reaction,the ratio of the time for $75 \% $ completion of a reaction to the time for $50 \% $ completion is $....$ . (Integer answer)

$A$ first order reaction is $75\%$ completed in $100 \ min$. How long will it take for its $87.5\%$ completion? (in $\min$)

At $298 \ K$,for a first order reaction $(A \rightarrow P)$ the following graph is obtained. The rate constant (in $s^{-1}$) and initial concentration (in $mol \ L^{-1}$) of '$A$' are respectively ($y$-axis $= \ln(a-x)$; $x$-axis $=$ time in sec).

The inactivation rate of a viral preparation is proportional to the amount of virus. In the first minute after preparation,$10 \%$ of the virus is inactivated. The rate constant for viral inactivation is $..... \times 10^{-3} \ min^{-1}$. (Nearest integer)
[Use : $\ln 10 = 2.303; \log_{10} 3 = 0.477; \text{property of logarithm} : \log x^y = y \log x$]

Half life of a first order reaction is $20 \ min$. The time taken to reduce the initial concentration of reactant to $(1/10)^{th}$ is $\qquad$ (in $min$)

Consider a certain reaction $A \rightarrow \text{Products}$ with $k = 2.0 \times 10^{-2} \ s^{-1}$. Calculate the concentration of $A$ remaining after $100 \ s$ if the initial concentration of $A$ is $1.0 \ mol \ L^{-1}$.