Question

what will the mole fraction of ethanol in a sample of spirit containing 85%ethanol by mass​

Answer 1

Answer : The mole fraction of ethanol in a sample of spirit is, 0.690

Explanation :

85 % ethanol by mass means, 85 grams of ethanol present in 100 grams of solution.

Mass of ethanol in solution = 85 g

Mass of solution = 100 g

Mass of water = 100 - 85 = 15 g

Molar mass of ethanol = 46 g/mole

Molar mass of water = 18 g/mole

Now we have to calculate the moles of ethanol and water.

$\text{Mole of ethanol}=\frac{\text{Mass of ethanol}}{\text{Molar mass of ethanol}}=\frac{85g}{46g/mole}=1.85mole$

$\text{Mole of water}=\frac{\text{Mass of water}}{\text{Molar mass of water}}=\frac{15g}{18g/mole}=0.83mole$

Now we have to calculate the mole fraction of ethanol.

$\text{Mole fraction of ethanol}=\frac{\text{Mole of ethanol}}{\text{Mole of ethanol}+\text{Mole of water}}$

$\text{Mole fraction of ethanol}=\frac{1.85mole}{1.85mole+0.83mole}=0.690$

Therefore, the mole fraction of ethanol in a sample of spirit is, 0.690