Question

$\times {10}^{24}$ hydrogen atoms are present in $18$ gms of water.

• A. 1.2
• B. 1.20

Answer 1

Answer: (A), (B)

Water has a molar mass of $18.01528\text{g}/\text{mol}\approx 18\text{g}/\text{mol}$.
So, in $18\text{g}$ of water, there will be
$\frac{18\text{g/}}{18\text{g/}/\text{mol}}=1\text{mol}$

Since water has a chemical formula of $H_{2}O$, there will be $2$ moles of hydrogen in every mole of water.

In one mole of water, there will exist approximately $6.02\cdot {10}^{23}$ water molecules.

So, there will be a total of $6.02\cdot {10}^{23}\cdot 2\approx 1.2\cdot {10}^{24}$ hydrogen atoms.