Question

Question 19
What is the fraction of the mass of water due to neutrons?

Answer 1

Mass of one mole (Avogadro Number) of neutrons ~ 1 g

Mass of one neutron $=\frac{1}{AvogadroNumber\left(N_A\right)}g$
Mass of one molecule of water $\frac{Molarmass}{N_A}=\frac{18}{N_A}g$
There are 8 neutrons in one atom of oxygen
Mass of 8 neutrons $=\frac{8}{N_A}$
Fraction of mass of water due to neutrons = $\frac{8}{18}$