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Some Basic Concepts of Chemistry question

2017 · Shift 0 · Q13
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Some Basic Concepts of Chemistry question

2017 · Shift 0 · Q13

JEE MainChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
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 1H atoms are replaced by 2H atoms is:
  1. A
    37.5 kg
  2. B
    7.5 kg
  3. C
    10 kg
  4. D
    15 kg
View written solutionFree

Correct answer: B

  1. Mass of hydrogen in a 75 kg person

Given that hydrogen constitutes 10.0%10.0\%10.0% of the body mass,

mH=0.10×75=7.5 kgm_{\text{H}} = 0.10 \times 75 = 7.5\text{ kg}mH​=0.10×75=7.5 kg

  1. Effect of replacing 1H^1\text{H}1H by 2H^2\text{H}2H

Ordinary hydrogen 1H^1\text{H}1H has mass approximately 1 u1\text{ u}1 u, while deuterium 2H^2\text{H}2H has mass approximately 2 u2\text{ u}2 u.

So, if every hydrogen atom is replaced by deuterium, the mass of the hydrogen portion doubles.

Initial hydrogen mass:

7.5 kg7.5\text{ kg}7.5 kg

Final mass of deuterium replacing it:

2×7.5=15.0 kg2 \times 7.5 = 15.0\text{ kg}2×7.5=15.0 kg

  1. Weight gained

The increase in mass is:

15.0−7.5=7.5 kg15.0 - 7.5 = 7.5\text{ kg}15.0−7.5=7.5 kg

  1. Match with options

Thus, the person would gain

7.5 kg\boxed{7.5\text{ kg}}7.5 kg​

So the correct option is B.

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