Kjeldahl's method estimates nitrogen by digesting the compound with concentrated sulphuric acid to convert nitrogen into ammonium sulphate, then liberating ammonia with alkali and absorbing it in a known amount of standard acid; the acid neutralised is equivalent to the ammonia, and hence to the nitrogen. The milliequivalents of acid neutralised equal volume times normality: 20 mL × 1.0 N = 20 meq of HCl, which equals 20 meq of NH_3 and therefore 20 meq of nitrogen. Mass of nitrogen = 20 × 14 / 1000 = 0.28 g, since the equivalent mass of nitrogen here equals its atomic mass 14. Percentage of nitrogen = (0.28 / 1.4) × 100 = 20%. Option 28% wrongly uses the nitrogen mass as the percentage directly without dividing by sample mass. Option 10% would arise from halving the acid equivalents. Option 40% would result from using a 0.7 g sample instead of 1.4 g. This calculation follows the standard NCERT formula %N = 1.4 × N_acid × V_acid / mass. Plausibility check: a 20% nitrogen content is chemically reasonable for many amides and amines, confirming the magnitude is sensible.