Question

46 g of ethyl alcohol is dissolved in 18 g of water. Calculate the mole fraction of ethyl alcohol. (at. wt. of C = 12, O = 16, H = 1).

Answer 1

Given: Mass of ethyl alcohol (C₂H₅OH) = 46 g

Mass of water (H₂O) = 18 g

Molar mass of C₂H₅OH = (2 × 12) + (6 × 1) + (1 × 16)

= 24 + 6 + 16

= 46 g/mol

Molar mass of H₂O = 2 × 1 + 16

= 18 g/mol

Moles of ethyl alcohol = `46/46` = 1 mol

Moles of water = `18/18` = 1 mol

`chi_"ethyl alcohol" = "Moles of alcohol"/("Moles of alcohol" + "Moles of water")`

= `1/(1 + 1)`

= 0.5

∴ Mole fraction of ethyl alcohol is 0.5.