What is the fraction of the mass of water due to neutrons?
The mass of 1 mole of a substance is equal to its relative atomic or molecular mass in grams.
Mass of one mole of neutrons = 1g
Mass of one neutron = 
No of neutrons in H = 0
No of neutrons in O = 8
Total neutrons in water (H2O) = 2 × 0 + 1 × 8 = 8
Mass of 8 neutrons = 
The molar mass of water = 18g
Mass of one molecule of water = 
Fraction of mass of water due to neutrons = 
= 0.444 = 44.44%
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