Some Basic Concepts of Chemistry - Result Question 12
####12. The most abundant elements by mass in the body of a healthy human adult are oxygen $(61.4 %)$, carbon $(22.9 %)$, hydrogen $(10.0 %)$, and nitrogen $(2.6 %)$. The weight which a $75 kg$ person would gain if all ${ }^{1} H$ atoms are replaced by ${ }^{2} H$ atoms is
(a) $15 kg$
(b) $37.5 kg$
(c) $7.5 kg$
(d) $10 kg$
(2017 JEE Main)
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Solution:
- Given, abundance of elements by mass oxygen $=61.4 %$, carbon $=22.9 %$, hydrogen $=10 %$ and nitrogen $=2.6 %$
Total weight of person $=75 kg$
$$ \text { Mass due to }{ }^{1} H=\frac{75 \times 10}{100}=7.5 kg $$
${ }^{1} H$ atoms are replaced by ${ }^{2} H$ atoms,
Mass due to ${ }^{2} H=(7.5 \times 2) kg$
$\therefore$ Mass gain by person $=7.5 kg$
