Question

In Tollen's test for aldehyde, the overall number of electrons(s) transferred to the Tollen's reagent formula \[\ce{[Ag(NH3)2]+}\] per aldehyde group to form silver mirror is ______. (Round off to the nearest integer)

Options

• 1

• 3

• 4

• 2

Answer 1

In Tollen's test for aldehyde, the overall number of electrons(s) transferred to the Tollen's reagent formula \[\ce{[Ag(NH3)2]+}\] per aldehyde group to form silver mirror is 2.

Explanation:

Two half reactions are

\[\ce{[Ag(NH3)3]+ + e- -> Ag + 2NH3}\]

\[\ce{RCHO + 3OH- -> RCO^-_2 + 2H2O + 2e-}\]

Overall reaction is

\[\ce{2[Ag(NH3)2]+ + RCHO + 3OH- -> 2Ag + RCO^-_2 + 4NH3 + 2H2O}\]

Therefore, for 1 mol \[\ce{R - CHO}\], 2 mol of \[\ce{[Ag(NH3)2]+}\] is reduced.