Give one chemical test to distinguish between the following pairs of compounds :
Acetaldehyde and benzaldehyde

Explanation

Acetaldehyde gives positive iodoform test, whereas benzaldehyde won.t give the test.
`underset("Acetadehyde")([CH_(3)CHO]) underset(I_(2)+NaOH)overset(NaOI)to underset("Iodoform")(CH_(3)I)+HCOO^(-1)Na^(+)`
Also, acetaldehyde and benzaldehyde can be distinguished with the help of Fehling.s reagent. Acetaldehyde is oxidised to ethanoate ion and a red precipitate of cuprous oxide is obtained in the process. Whereas ben zaldehyde does not react with Fehling.s reagent.
`underset("Acetaldehyde")(C_(2)H_(5)CHO) +2Cu^(2+) +5OH^(-) to CH_(3)COO^(-) +Cu_(2)O +3H_(2)O`