How much ethyl alcohol must be added to 1 litre of water so that the solution will freeze at `- 14^@C` ? (Kf for water = `1.86^@C`/mol)

Options

A. 7.5 mol
B. 8.5 mol
C. 9.5 mol
D. 10.5 mol

Answer

A

Explanation

`Delta T_(f) = K_(f)m`
`Delta T_(f) = K_(f) (n_(2) xx 1000)/(W_(1))`
`14 = 1.86 xx (n_(2) xx 1000)/(1000)`
`n_(2) = 7.5` mol