The number of groups present in a tripeptide Asp–Glu–Lys is ____.

The incorrect statement is :

The decreasing order of reactivity of the following compounds towards nucleophilic substitution (S_N2) is :

An acidic solution of dichromate is electrolyzed for 8 minutes using 2A current. As per the following equation
Cr₂O₇^2- + 14H⁺ + 6e^– $$ \to $$ 2Cr³⁺ + 7H₂O
The amount of Cr³⁺ obtained was 0.104 g. The efficiency of the process(in%) is (Take : F = 96000 C, At. mass of chromium = 52) ______.