The vapor pressure of ethanol is 54.68 mm Hg at 25°C. How many grams of chlorophyll, C55H72MgN4O5, a nonvolatile, nonelectrolyte (MW = 893.5 g/mol), must be added to
174.9 grams of ethanol to reduce the vapor pressure to 53.25 mm Hg ?
ethanol = CH3CH2OH = 46.07 g/mol.
___g chlorophyll?

88.19 g

Explanation:

From Raoult's law;

P° - P/P° = XB

XB = mole fraction of solute = number of moles of solute(n)/number of moles of solute(n) + number of moles of solvent (N)

But N>>n

So,

XB = number of moles of solute/number of moles of solvent

Number of moles of solute = mass of solute (WB)/molar mass of solute (MB)

number of moles of solvent = mass of solvent (WA)/molar mass of solvent (MA)

Hence;

P° - P/P° = WB/MB * MA/WA

WB = (P° - P/P°) (MB * WA/MA)

Substituting values;

WB = (54.68 - 53.25/54.68) * (893.5 * 174.9/46.07)

WB = 88.19 g