The solubility of sodium bicarbonate in water is 9.6 g/100 g at 20°C and 16.4 g/100 g at 60°C. If a saturated solution of sodium bicarbonate at 60°C is cooled to 20°C, the percentage of the dissolved salt crystallized out will be

The percentage of salt crystallized out is calculated based on the difference in solubility between 60 degrees Celsius and 20 degrees Celsius per unit of solvent. Starting with 16.4 g of solute per 100 g of water at the higher temperature, dropping to 9.6 g means 16.4 minus 9.6 equals 6.8 g precipitates out of the 16.4 g initially dissolved. Calculating 6.8 divided by 16.4 and multiplying by 100 gives approximately 41.5 percent.