Question

Find the amount of water present, if the total number of protons is $1.8069\times {10}^{25}$.

• A. $108\text{g}$
• B. $10.8\text{g}$
• C. $54\text{g}$
• D. $36\text{g}$

Answer 1

The correct option is C $54\text{g}$

No. of protons in one molecule of $H_{2}O=8+2=10$ protons
No. of protons in one mole of $H_{2}O$
$=10\times 6.023\times {10}^{23}=6.023\times {10}^{24}protons$

Given number of protons $=1.8069\times {10}^{25}$

So, the number of moles of $H_{2}O$,
$=\frac{\text{Given number of protons}}{\text{number of protons present in one mole of}{H}_{2}O}$
$=\frac{1.8069\times {10}^{25}}{6.023\times {10}^{24}}=3\text{moles}$
Mass of one mole of $H_{2}O$ is $18\text{g}$
So, the mass of $H_{2}O=3\times 18=54\text{g}$
54 g of water is present.