પાણીના મોલ \(=\frac{1000}{18}\)
ઇથેનોલના મોલ-અંશ \(=\frac{\frac{W}{46}}{\frac{W}{46}+\frac{1000}{18}}\)
\(\therefore 0.2=\frac{1}{5}=\frac{\frac{W}{46}}{\frac{18 W+46000}{46 \times 18}}\)
\(\therefore 18\,W +46000=90\,W\)
\(\therefore W=\frac{46000}{72}=\frac{5750}{9}\)
\(=638.89\,g\)
(આપેલ છે: આણ્વિય દળ ${C}=12, {H}=1, {O}=16 {u}$ )