Question

Calculate no. of atoms in $118$g of water.

• A. $1.18\times {10}^{25}$
• B. $1.18\times {10}^{24}$
• C. $1.18\times {10}^{22}$
• D. $1.18\times {10}^{26}$

Answer 1

The correct option is A $1.18\times {10}^{25}$

$118g$ water $=\frac{118}{18}moles$ of water

$(\frac{givenmass}{molarmass}=numberofmoles)=6.55moles$

$1mole$ has $N_A$ number of molecules.

$14.75moles=6.023\times 6.55\times {10}^{23}molecules=39.484\times {10}^{23}molecules$

$1$ water molecule has $3$ atoms.

$\therefore 118g$ water has $=39.484\times 3\times {10}^{23}$

$=118.45\times {10}^{23}atoms$

$=1.18\times {10}^{25}atoms$

Hence, te correct option is $\text{A}$