Question

A solution contains 200 g ppm $CaC{O}_3$. If there is $\frac{x\times N_A}{{10}^6}$ $CaC{O}_3$ molecules per gram, what is the value of $x$?

Answer 1

Given, a solution contains $200$ g parts per millimoles (out of ${10}^6$ g)

$=\frac{200}{100}$moles of $CaC{O}_3$ per million gram $=2moles=2000$ millimoles $CaC{O}_3$ per million gram

This implies $\frac{2000}{{10}^6}=2\times {10}^{-3}$ millimoles per gram.

$2$ moles $CaC{O}_3$

$=2\times N_A$ molecules $CaC{O}_3$ per million gram

$=\frac{2\times N_A}{{10}^6}$ molecules per gram.

Hence, the value of $x$ is $2.$