Part 2 I. The density of a 50% water and 50% hanol mixture, by mass, is 0.913 g/
ID: 548688 • Letter: P
Question
Part 2 I. The density of a 50% water and 50% hanol mixture, by mass, is 0.913 g/mL. Note: the molar masses of water by mass, and ethanol are 18 0 g and 460g the universal gas constant R is 0.0821 L-atm/mol-K. Calculate the molality of this solution assuming that water 8 and 4çQ g the universal gas constant R is 0,0821 L-atm/molK. a. is the solvent in this case. b. Calculate the molarity of this solution assuming that water is the solvent in this case. c. Calculate the mole fractions of water and ethanol in this solution. Calculate the total vapor pressure of this solution if the vapor pressure of pure water at 25 °C is 0.03 atm and the vapor pressure of ethanol is O.0724 atm. Assuming that water is the solvent, calculate the osmotic pressure of this solution at 25 °C. e.Explanation / Answer
Given 50 % water and 50 % ethanol by mass
assuming 100 g basis
50 g of water , 50 g of ethanol
molar mass of water. 18 g/mol and ethanol is 46 g/mol
NO. of moles of water = 50 g / 18 g/mol = 2.78 moles and for ethanol = 50 g / 46 g/mol = 1.09 moles
Total no. of moles = 2.78 + 1.09 = 3.87 moles
Mole fraction of water Xa = 2.78 moles / 3.87 moles = 0.718
Mole fraction of ethanol Xb = 1.09 moles / 3.87 moles = 0.282
Vapor pressure of water Pa = 0.03 atm
Vapor pressure of ethanol Pb = 0.0724 atm
Total Vapor pressure of solution Po = Pa * Xa + Pb * Xb = 0.03 atm * 0.718 + 0.0724 atm * 0.282 = 0.042 atm
Answer for (d) 0.042 atm
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Given
Total mass of solution = 100 g (basis as taken in (d))
Volume of solution = Mass * density = 100 g * 0.913 g/ml = 91.3 ml = 0.0913 L
No. of moles of ethanol in 100 g of solution = 1.09 moles
Molarity of ethanol = 1.09 moles / 0.0913 L = 11.94 mol/L ( or M)
Osmotic pressure Pi = i MRT
i - vant hoff factor of ethanol = 1
M - molarity of solution = 11.94 M (or mol/L)
R - universal gas constant = 0.08206 L.atm /mol.K
T - temperature of solution = 25 C = 298 K
Pi = 1 * 11.94 mol/L * 0.08206 L.atm/mol.K * 298 K = 291.95 atm
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