Some Basic Concepts of Chemistry 1 Question 12
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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 $75 \mathrm{~kg}$ person would gain if all ${ }^{1} \mathrm{H}$ atoms are replaced by ${ }^{2} \mathrm{H}$ atoms is
======= ####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 $75 \mathrm{~kg}$ person would gain if all ${ }^{1} \mathrm{H}$ atoms are replaced by ${ }^{2} \mathrm{H}$ atoms is
3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed (a) $15 \mathrm{~kg}$
(b) $37.5 \mathrm{~kg}$
(c) $7.5 \mathrm{~kg}$
(d) $10 \mathrm{~kg}$
(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 $=75 \mathrm{~kg}$
$$ \text { Mass due to }{ }^{1} \mathrm{H}=\frac{75 \times 10}{100}=7.5 \mathrm{~kg} $$
${ }^{1} \mathrm{H}$ atoms are replaced by ${ }^{2} \mathrm{H}$ atoms,
Mass due to ${ }^{2} \mathrm{H}=(7.5 \times 2) \mathrm{kg}$
$\therefore$ Mass gain by person $=7.5 \mathrm{~kg}$
