15g ethanol is dissolved in enough water to make 150ml solution. The solution de

Question

15g ethanol is dissolved in enough water to make 150ml solution. The solution density is 0.981g/ml. (A) calculate the molality of ethanol in solution (B) calculate the mole fraction of ethanol and water in solution. 15g ethanol is dissolved in enough water to make 150ml solution. The solution density is 0.981g/ml. (A) calculate the molality of ethanol in solution (B) calculate the mole fraction of ethanol and water in solution. 15g ethanol is dissolved in enough water to make 150ml solution. The solution density is 0.981g/ml. (A) calculate the molality of ethanol in solution (B) calculate the mole fraction of ethanol and water in solution.

Explanation / Answer

A)

density = 0.981 g/ml

mass of ethanol = 15 g

moles = 15 / 46 = 0.326

volume = 150 mL = 0.15 L

Molarity = moles / volume = 0.326 / 0.150 = 2.17

Molarity = 2.17 M

B)

moles of ethanol = 0.326

mass of solution = 150 x 0.981 = 147.15 g

mass of solvent = 147.15 - 15 = 132.15 g

moles of water = 132.15 / 18 = 7.34

total moles = 7.34 + 0.326 = 7.666

mole fraction of ethanol = 0.326 / 7.666 = 0.0425

mole fraction of water = 7.34 / 7.666 = 0.958

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