The concentration of a substance undergoing a chemical reaction becomes one-half of its original value after time,regardless of the initial concentration. The reaction is an example of a

$A$ first order reaction is $75 \%$ completed in $60 \ min$. The time required for its $50 \%$ completion is: (in $min$)

$A$ substance $A$ decomposes by a first order reaction starting initially with $[A]_0 = 2.00 \, M$ and after $200 \, \min$,$[A]_t = 0.15 \, M$. For this reaction,what is the value of the rate constant $k$?

Gaseous cyclobutene isomerizes to butadiene in a first order process which has a $k$ value of $3.3 \times 10^{-4} \ s^{-1}$ at $153^{\circ}C$. The time in minutes it takes for the isomerization to proceed $40\%$ to completion at this temperature is ..........
(Rounded off to the nearest integer)

$t_{87.5}$ is the time required for the reaction to undergo $87.5 \%$ completion and $t_{50}$ is the time required for the reaction to undergo $50 \%$ completion. The relation between $t_{87.5}$ and $t_{50}$ for a first order reaction is $t_{87.5} = x \times t_{50}$. The value of $x$ is $......$. (Nearest integer)

The reaction $A + B \xrightarrow{k}$ product is first order with respect to $A$ and zero order with respect to $B$. If $a_0$ and $a_t$ are the concentrations of $A$ at $t = 0$ and after time $t \, sec$ respectively,then select the correct relationship -