Respuesta :
Answer : The mass percent of ethanol is, 10.38 % and the molality of ethanol is, 2.52 mole/kg
Explanation :
In wine, the solute and solvent are ethanol and water respectively.
Given :
12.8 % ethanol by volume means 12.8 mL ethanol present in 100 mL solution.
Volume of ethanol = 12.8 mL
Volume of solution = 100 mL
Volume of water = 100 - 12.8 = 87.2 mL
Density of ethanol = [tex]0.789g/cm^3=0.789g/mL[/tex]
Density of water = 1 g/mL
Now we have to calculate the mass of ethanol and water.
[tex]\text{Mass of ethanol}=\text{Density of ethanol}\times \text{Volume of ethanol}=0.789g/mL\times 12.8mL=10.1g[/tex]
and,
[tex]\text{Mass of water}=\text{Density of water}\times \text{Volume of water}=1g/mL\times 87.2mL=87.2g[/tex]
Now we have to calculate the total mass of 100 mL of wine.
Total mass of 100 mL of wine = 10.1 + 87.2 = 97.3 g
Now we have to calculate the mass percent of ethanol.
[tex]\text{Mass of percent of ethanol}=\frac{\text{Mass of ethanol}}{\text{Total mass of solution}}\times 100[/tex]
[tex]\text{Mass of percent of ethanol}=\frac{10.1g}{97.3g}\times 100=10.38\%[/tex]
The mass percent of ethanol is, 10.38 %
Now we have to calculate the molality.
[tex]Molality=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Mass of solvent}}[/tex]
Molar mass of ethanol = 46 g/mole
[tex]Molality=\frac{10.1g\times 1000}{46g/mole\times 87.2g}=2.52mole/kg[/tex]
The molality of ethanol is, 2.52 mole/kg
