Question

A 40-ml vial is filled with 20 mL of water and sealed at 20°C. Then I spike 3.0 μL of Methyl Chloride (CH₃Cl) into the vial and shake it until the Methyl Chloride distributes itself between the air and water.

Where will the Methyl Chloride end up? Explain?

(a) Mostly in the air

(b) Mostly in the water

(c) Equal amounts in the air and water

Answer 1

When 3uL of methyl chloride is dissolved in 20mL water in 40 mL vial it will end up equally in the air and water.

Since methyl chloride is highly soluble in water ap-prox 303 ml / 100 ml at 20^oC , the shaking will cause most of it to dissolve in water.

Now the vapour pressure of the methyl chloride is also very high approx 3800 mmHg , so it is highly volatile .

The evaporization of it will cause its significant amounts in air too , and hence it will be present in both air and water equally .