Question: is picric acid a strong acid?
Answer: A STRONG ACID is one whose conjugate base is MOST stable. In picric acid, the (NO2) groups exert -R(electron withdrawing resonance effect) and -I(electron withdrawing inductive effect). ... This is the reason why 2,4,6-trinitrophenol is regarded as a VERY STRONG acid(pka=1.02) even though it lacks a COOH group.