Question

Ordinary water contains one part of heavy water per 6000 parts by weight.The number of heavy watermolecules present in a drop of water of volume 0.01 ml is (Density of water is 1 g/ml)

• A. 2.5 X 1016
• B. 2.5 X 1017
• C. 5 X 1016
• D. 7.5 X 1016

Answer 1

The correct option is C

5 X 1016

$\frac{H_{2}O}{6000}$ $\frac{D_{2}O}{1}$

0.01 x

$x=\frac{1\times 0.01}{6000}=1.66\times {10}^{-6}$

$20gm\to 6.023\times {10}^{23}$

$1.66\times {10}^{-6}\to x$

$x=\frac{1.66\times {10}^{-6}\times 6.023\times {10}^{23}}{20}=5\times {10}^{16}$