A first order reaction has a rate constant `1.15xx10^(-3)s^(-1)`. How long will `5g` of this reactant take to reduce to `3g`` ?

Explanation

For the first order reaction,
`t = 2.303/k log a/(a-x)`
`a=5g, (a-x) = 3g, k = 1.15 xx 10^(-3)s^(-1)`
`t= 2.303/(1.15 xx 10^(-3)s^(-1)) log (5g)/(3g) = 2.303/(1.15 xx 10^(-3)s^(-1))(log 5-log3)`
`=(2.303)/(1.15 xx 10^(-3)s^(-1))(0.6990 - 0.4771)`
`=(2.303)/(1.15 xx 10^(-3)s^(-1)) xx 0.2219 = 444s`