$A$ first order reaction has a rate constant of $1.5 \times 10^{-3} \ s^{-1}$. How long will $5.0 \ g$ of this reactant take to reduce to $3.0 \ g$?

The rate constant of a first order reaction is $15 \times 10^{-3} \ s^{-1}$. How many seconds will $5.0 \ g$ of this reactant take to reduce to $3.0 \ g$?

$A$ radioactive substance decomposes such that after $100 \ min$,its concentration becomes $1/8$ of the original concentration. Calculate the rate constant $(k)$ and half-life time $(t_{1/2})$.

$A$ flask is filled with equal moles of $A$ and $B$. The half-lives of $A$ and $B$ are $100 \, s$ and $50 \, s$ respectively and are independent of the initial concentration. The time required for the concentration of $A$ to be four times that of $B$ is $.... \, s.$
(Given : $\ln 2 = 0.693$ )

The half-life of a first-order reaction $X \longrightarrow Y + Z$ is $3 \ minutes$. What is the time required to reduce the concentration of $X$ by $90 \%$ of its initial concentration?

In a $1^{st}$ order reaction,$75\%$ of the reactant is consumed in $1.388 \, h$. Find the rate constant of the reaction.