When a specific amount of acetone (C3H6O) is added to 100.0 g of pure water at 65°C, the vapor pressure of water over the solution is lowered by 1.556 kPa. Given the vapor pressure of water at 65°C is 25.022 kPa, what is the mass of acetone added?

The mass of acetone that must be added is 4.101 grams

Explanation:

The relative lowering of vapor pressure is directly proportional to the amount of dissolved solute.

The equation used to calculate relative lowering of vapor pressure follows:

where,

= relative lowering in vapor pressure  = 1.556 kPa

i = Van't Hoff factor = 1 (for non electrolytes)

= mole fraction of solute = ?

= vapor pressure of pure water = 22.022 kPa

Putting values in above equation, we get:

As, the mole fraction of acetone is 0.0707. This means that 0.0707 moles are present in the solution

To calculate the number of moles, we use the equation:

Molar mass of acetone = 58 g/mol

Moles of acetone = 0.0707 moles

Putting values in above equation, we get:

Hence, the mass of acetone that must be added is 4.101 grams

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.