Calculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is 0.040. ( assume the density of water to be one).

Explanation

Molarity means, the number of moles of the solute in 1 litre of the solution.
Mole of `H_(2)O` in 1 litre `=(1000g)/(18) = 55.55` mole
For binary solution, `X_(1)+X_(2)=1`
`X_(H_(2)O) = 1 - X_(C_(2)H_(5)OH)`
`X_(H_(2)O)=1-0.040=0.96`
`X_(H_(2)O)=(n_(H_(2)O))/(n_(H_(2)O)+n_(C_(2)H_(5)OH))`
`0.96=(55.55)/(55.55+n_(C_(2)H_(5)OH))`
`53.328 + 0.96 n_(C_(2)H_(5)OH)=55.55`
`n_(C_(2)H_(5)OH)=(2.222)/(0.96) = 2.3145` mole
In 1 L solution 2.3145 mole `=2.3145`