Question

Calculate the vapor pressure of a solution containing 25.2 gg of glycerin (C3H8O3)(C3H8O3) in 124 mLmL of water at 30.0 ∘C∘C. The vapor pressure of pure water at this temperature is 31.8 torrtorr. Assume that glycerin is not volatile and dissolves molecularly (i.e., it is not ionic) and use a density of 1.00 g/mLg/mL for the water.

Answer 1

Answer:

29.256 torr.

Explanation:

Number of moles

Glycerin:

Molecular weight of glycerin = (12*3) + (1*8) + (16*3)

= 36 + 8 + 48

= 92 g/mol

Number of moles = mass/molar mass

= 25.2/92

= 0.274 mol

Water:

Converting g/ml to g/l,

1000 ml = 1 l

= 1 g/ml * 1000 ml/1l

= 1000 g/l

Mass = (density * volume)

= 1000*0.124

= 124 g.

Molar mass of water = (1*2) + 16

= 18 g/mol

Number of moles = mass /molar mass

= 126/18

= 6.89 mol

P°solution = xsolvent * P°solvent

Where,

xwater = xsolvent = mole fraction of water.

Mole fraction is defined as the number of moles of a component of a solution divided by the total number of moles present in that solution.

xwater = mole of water/total mole of solution

Total mole = 6.89 + 0.274

= 7.164 moles

xwater = 6.89/7.164

= 0.962

P°solution = xsolvent * P°solvent

P°solution = 31.8 * 0.962

= 29.256 torr