Question

Find the number of neutrons in $0.45$ g water, assuming that all the hydrogen atoms are $H^1$ atoms and all the oxygen atoms are $O^{16}$atoms.

• A. $1.1\times {10}^{23}$
• B. $1.2\times {10}^{23}$
• C. $1.3\times {10}^{23}$
• D. $1.4\times {10}^{23}$

Answer 1

Answer: (B)

$1.2\times {10}^{23}$

$0.45$ g water corresponds to $\frac{0.45}{18}=0.025$ moles.
This corresponds to $0.025\times 6.023\times {10}^{23}=1.506\times {10}^{22}$ molecules.
Thus, the total number of neutrons present is $8\times 1.506\times {10}^{22}=1.2\times {10}^{23}$ neutrons.