Question

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

Answer 1

Hint: We need to know that when the prevalence of interest are those of individual chemical elements, rather than of compounds or other substances, the term mass fraction can also refer to the ratio of the mass of an element to the total mass of a sample.

Complete answer:
To solve this question we must know the mass of water since it has two hydrogen atoms and one oxygen atom thus the total mass will be two plus sixteen which makes it eighteen. The number of neutrons in hydrogen is zero while in the case of oxygen it is eight, which is the difference between mass number and number of protons. Number of protons is equal to the atomic number of atoms or any compound. So after knowing the individual number of neutrons for hydrogen and oxygen we will add so as to get the total number of neutrons in water thus. Number of neutrons is equal to eight.
Water $\left( {{H_2}O} \right)$ =Total mass $ = 1 + 1 + 16 = 18g/mol$
No. of neutrons in $H = 0$ (in protium)
No. of neutrons in $O = 8$ i.e. $8g/mol$
Total neutrons in water $\left( {{H_2}O} \right) = \left( {2 \times 0} \right) + \left( {1 \times 8} \right) = 8g/mol$
% mass neutrons in water = $ \dfrac{8}{{18}} = 0.044 = 44.44\% $

Note:
We have to know that the water consists of a total of ten protons, eight neutrons, and ten electrons. Mole fraction is a ratio of moles to moles; molar concentration is a quotient of moles to volume. The mole fraction is one way of expressing the composition of a mixture with a dimensionless quantity; mass fraction (percentage by weight, wt%) and volume fraction (percentage by volume, volume%) are others.