Mole of C3H7OH = Mass of C3H7OH (g) Molar mass of C3H7OH (g/mol) 142 g 60.09 g/mol = 2.3631 mol C3H7OH =
Mole of H2O = Mass of H2O (g) Molar mass of H2O (g/mol) 58.0 g 18.02 g/mol = 3.2186 mol H2O =
XC3H7OH = Mole of C3H7OH + Mole of H2O Mole of C3H7OH = 0.423 = 2.3631 mol + 3.2186 mol 2.3631 mol
XH2O = Mole of C3H7OH + Mole of H2O Mole of H2O = 0.577 = 2.3631 mol + 3.2186 mol 3.2186 mol
Alternative way: XC3H7OH + XH2O = 1.000 – 0.423 = 1.000 XH2O = 0.577
A sample of commercial concentrated hydrochloric acid is 11.8 M HCl and has a density of 1.190 g/mL. Calculate the mass %, molality, and mole fraction of HCl. EXERCISE – 31 1.2 SK015
Moles of HCl Volume of solution (in L) Assume: volume of solution = 1.0 L So, moles of HCl = 11.8 mol Molarity = (11.8 M) Mass of HCl = Mole of HCl x Molar mass of HCl = 11.8 mol x 36.45 g/mol = 430.11 g HCl
Density of solution = Mass of solution Volume of solution Mass of solution = 1.190 g/mL x 1000 mL = 1190 g solution
Mass % Mass of solute (HCl) Mass of solution = x 100 430.11 g 1190 g = x 100 = 36.2 %
Mass of solution = mass of HCl + mass of solvent Mass of solvent = 1190 g – 430.11 g = 759.89 g solvent = 0.760 kg solvent
Molality = Moles of solute (HCl) Mass of solvent (in kg) = 11.8 mol 0.760 kg = 15.5 m HCl solution
Moles of HCl = 11.8 mol Mass of solvent (H2O) = 759.89 g H2O Mole of H2O = Mass of H2O (g) Molar mass of H2O (g/mol) 759.89 g 18.02 g/mol = 42.17 mol H2O =
Moles of HCl = 11.8 mol Mole of H2O = 42.17 mol H2O Mole fraction of HCl Mole of HCl Mole of HCl + Mole of H2O = 11.8 mol 11.8 mol + 42.17 mol = = 0.219