Chemistry 30

Use a solubility curve to determine the solubility of the following compounds at the temperatures given.

For each of the following solutions, classify the solution as unsaturated, saturated, or supersaturated.

What is the solubility of ammonium chloride, NH₄Cl, at 100°C? Express this both as g ·100mL^-1 and as mol·L^-1

Solution:

From the Solubility Curve table we find that the solubility of NH₄Cl at 100°C is approximately 75 g ·100mL^-1.

To convert this to molarity (mol·L^-1) we will need to know the molar mass of NH₄Cl (a refresher):

Next, we need to convert 75 g ·100mL^-1 (= 750 g ·1000mL^-1 = 750 g ·1L^-1) to mol·L^-1, the units for molarity

Begin by converting 75 g ·100mL^-1 to g ·L^-1 which will simply our conversion to molarity (mol·L^-1):

Next

Solution

At that temperature any mass up to approximately 32g could be dissolved in 100mL of water.

Solution

At 80°C, approximately 50g of KCl will dissolve in 100g of water. At 40°C only 38g of KCl will dissolve in 100g of water. Therefore, when the solution is cooled from 80°C to 40°C, approximately 12g of potassium chloride will come out of solution, forming a solid.