Question

The volume of one mole of water at $277K$ is $18ml$. One $ml$ of water contains $20$ drops. The number of molecules in one drop of water will be $(N_A=6\times {10}^{23})$

• A. $1.07\times {10}^{21}$
• B. $1.67\times {10}^{21}$
• C. $2.67\times {10}^{21}$
• D. $1.67\times {10}^{20}$

Answer 1

The correct option is B $1.67\times {10}^{21}$

$1$ mole $=185ml$ (given)
$1ml=20drops$

$\therefore 1$ mole $=18\times 20$
$=3360drops$.

$1$ mole $=6.022\times {10}^{23}$ molecules

$\Rrightarrow 360drops=6.022\times {10}^{23}$ molecules

$\therefore 1drops=x$ molecules
$360\times x=1\times 6.022\times {10}^{23}$
$x=1.67\times {10}^{21}$ molecules

Hence, Option $B$ is the correct answer.