Question

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

Options

• 7.5 mol

• 8.5 mol

• 9.5 mol

• 10.5 mol

Answer 1

7.5 mol

Explanation:

ΔT_f = K_f m

ΔTf = `"K"_"f" ("n"_2 xx 1000)/"w"_1`

`14 = 1.86 xx ("n"_2 xx 1000)/1000`

`"n"_2` = 7.5 mol