Question

The vapor pressure of ethanol is 54.68 mm Hg at 25oC.

How many grams of chlorophyll , C55H72MgN4O5, a nonvolatile, nonelectrolyte (MW = 893.5 g/mol), must be added to 207.6 grams of ethanol to reduce the vapor pressure to 53.60 mm Hg ?

ethanol = CH3CH2OH = 46.07 g/mol.

Answer 1

delta P = 54.68-53.60 = 1.08 mm
delta P = 1.08 = Xchlor*P^o_solvent
1.08 = Xchlor*54.68
Solve for X chlorophyll

Then Nc = mols chlorophyll
and Netoh = mols ethanol

(Nc)/(Nc+Netoh) = X chlorophyll from above.
Solve for Nc

Then convert to grams.
g chlorophyll = mols chlorophyll x molar mass chlorophyll.
Post your work if you get stuck.