Which of the following specific nitrogen-containing compounds will give a positive Prussian blue col — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Azobenzene contains an azo group ($-N=N-$). While it contains both carbon and nitrogen and will successfully form $NaCN$ during sodium fusion (yielding a positive Lassaigne's test), compounds with azo groups cannot be quantitatively converted to $(NH_4)_2SO_4$ upon digestion with concentrated $H_2SO_4$. Hence, Kjeldahl's method fails for azobenzene.