Question

$\frac{3}{4}$ part of radioactive compound undergoes decay in 2h. Calculate its half-life time.

• A. $60min$
• B. $45min$
• C. $30min$
• D. $15min$

Answer 1

Answer: (A)

$60min$

$\lambda =\frac{2.303}{t}\log \frac{a}{a-x}$
$=\frac{2.303}{2}\log \frac{a}{a-\frac{3}{4}a}=\frac{2.303}{2}\log 4$
$=2.303\log 2=0.693h^{-1}$
$t_{1/2}=\frac{0.693}{\lambda }=\frac{0.693}{0.693}=1h=60min$