JEE Main 2017 Chemistry question
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 75kg person would gain if all H atoms are replaced by H atoms is
Answer: (A)
Solution
Mass of hydrogen = 10% of 75 kg = 7.5 kg. Replacing H by H doubles this mass, so the gain is 7.5 kg.