Question

The half-life of tritium is 12.5 years. What mass of tritium of initial mass 64 mg will remain undecayed after 50 years ?

• A. 32 mg
• B. 8 mg
• C. 16 mg
• D. 4 mg

Answer 1

Answer: (D)

4 mg

Answer 2

$m =\frac{ m _{0}}{2^{ n }}$ $t = nT$ $50= n \times 1.25$ $\Rightarrow n =4$ $\therefore m =\frac{ m _{0}}{2^{4}}$ $=\frac{64}{16}$ $=4 \, mg$