A `0.535` gm mixture of ethanol and acetaldehyde when heated with Fehling's solution gave `1.2` gm of a red precipitate. What is the percentage of acetaldethyde in the mixture ?

Explanation

Let three be x gm of `CH_(3)CHO` and `(0.535-x gm)` of `C_(2)H_(5)OH`.

(Only aldehyde reacts with Fehiling's solution, not alcohol)
1 mol of `underset((44gm))(CH_(3)CHO=1)` mol of red ppt. of `underset((143gm))(Cu_(2)O)`
143 gm of precipitate is obtained from 44 gm of `CH_(3)CHO`. `1.2` gm of precipitate is obtained from:
`implies (4)/(143)xx1.2~~0.348` gm of `CH_(3)CHO`
`%` of `CH_(3)CHO=(0.368)/(0.535)xx100~~68.8%`