A solution is prepared by dissolving 20.2 ml of methanol (ch3oh) in 100.0 ml of water at 25oc. the final volume of the solution is 118 ml. the densities of methanol and water at this temperature are 0.782 g/ml and 1.00 g/ml, respectively. for this solution, calculate the molarity, molality, percent by mass, mole fraction, and mole percent.

Question

Chemistry

Janet Mann

27 April, 20:44

A solution is prepared by dissolving 20.2 ml of methanol (ch3oh) in 100.0 ml of water at 25oc. the final volume of the solution is 118 ml. the densities of methanol and water at this temperature are 0.782 g/ml and 1.00 g/ml, respectively. for this solution, calculate the molarity, molality, percent by mass, mole fraction, and mole percent.

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Lamont Manning · Answer 1

M (CH₃OH) = 20,2 ml · 0,782 g/ml.

m (CH₃OH) = 15,8 g.

n (CH₃OH) = 15,8 g : 32 g/mol.

n (CH₃OH) = 0,493 mol.

m (H₂O) = 100 ml · 1 g/ml.

m (H₂O) = 100 g.

n (H₂O) = 100 g : 18 g/mol.

n (H₂O) = 5,55 mol.

1) c (CH₃OH) = 0,493 mol : 0,118 dm³.

c (CH₃OH) = 4,18 mol/dm³.

2) b (CH₃OH) = 0,493 mol : 0,1 kg.

b (CH₃OH) = 4,93 mol/kg.

3) moll fraction = 0,493 mol : 6,043 mol = 0,081.

4) percent by mass = 15,8 g : 115,8 g = 0,136 = 13,6%.

5) 0,493 mol : 6,043 mol = 8,1%.