Question

What weight of sodium nitrate will separate when a saturated solution containing 50 gram of water is cooled from ${50}^{\circ }C$ to ${30}^{\circ }C$ ? The solubility of $NaN{O}_3$ at ${50}^{\circ }C$ and ${30}^{\circ }C$ is 114 g and 86 g respectively.

Answer 1

$100g$ of water will dissolve $114g$ of sodium nitrate at $50$ degree celsius and $86$ g at $30$ degree celsius.

1 g of water will dissolve $1.14$ g of sodium nitrate at 50 degree celsius and $0.86$ g at $30$ degree celsius.$50$ g of water will dissolve $1.14\times 50=57$ g of sodium nitrate at $50$ degree celsius and $0.86\times 50=43$ g at $30$ degree celsius.

Separation of sodium nitrate out of saturated solution is due to decrease in solubility of sodium nitrate in water with decrease in temperature.

Weight that will separate out from $50$ g of water $=57-43g=14$ g.