Tollen’s reagent is used for the detection of aldehyde, when a solution of AgNO3 is added to glucose with NH4OH then gluconic acid is formed.
Ag++e−→Ag; E∘red=0.8V
C6H12O6+H2O→C6H12O7 (Gluconic acid) +2H++2e;E∘oxd=−0.05V
Ag(NH3)+2+e−→Ag(S)+2NH3;E∘=–0.337V
[Use 2.303×RTF=0.0592 and FRT=38.92 at 298 K]
(i) 2Ag++C6H12O6+H2O→2Ag(s)+C6H12O7+2H+. Find ln K of this reaction.
58.38
2Ag++2e→2Ag ΔG=−2F×0.8 (reduction half)
C6H12O6+H2O→C6H12O7+2H++2e ΔG=−2F×(−0.05)(oxidation half)2Ag++C6H12O6+H2O→2Ag+C6H12O7+2H+ ΔG0=−1.5F
ΔG0=−RTlnK
−1.5×F=–RT ln K
FRT=38.92 at 298 K
lnK=1.5×38.92≈58.32