Answer: 11.2 days
Explanation:
Expression for rate law for first order kinetics is given by:
[tex]t=\frac{2.303}{k}\log\frac{a}{a-x}[/tex]
where,
k = rate constant
t = age of sample
a = let initial amount of the reactant
a - x = amount left after decay process
a) for completion of half life:
Half life is the amount of time taken by a radioactive material to decay to half of its original value.
[tex]t_{\frac{1}{2}}=\frac{0.693}{k}[/tex]
[tex]k=\frac{0.693}{5.6days}=0.124days^{-1}[/tex]
b) for completion of 75% of reaction
[tex]t=\frac{2.303}{0.124}\log\frac{100}{100-75}[/tex]
[tex]t=\frac{2.303}{0.124}\log\frac{100}{25}[/tex]
[tex]t=11.2days[/tex]
The time for which she has to perform the experiment is 11.2 days
