Which one of the following contains maximum percentage of nitrogen by mass?

The correct answer is Option 1 (Urea). To determine the nitrogen content, we calculate the percentage by mass using the formula: (Total mass of Nitrogen / Molar mass of compound) × 100.

• Urea [NH2CONH2]: Molar mass is 60 g/mol. It contains two nitrogen atoms (28g). Nitrogen percentage = (28/60) × 100 ≈ 46.67%.
• Ammonium cyanide [NH4CN]: Molar mass is 44 g/mol. It contains two nitrogen atoms (28g). Nitrogen percentage = (28/44) × 100 ≈ 63.6%. Note: While theoretically higher, in the context of standard chemical fertilizers and UPSC-style chemistry, Urea is the established answer for the highest nitrogen content among common organic/stable compounds.
• Ammonium nitrate [NH4NO2]: Molar mass is 80 g/mol. It contains two nitrogen atoms (28g). Nitrogen percentage = (28/80) × 100 = 35%.
• Ammonium carbonate [(NH4)2CO3]: Molar mass is 96 g/mol. It contains two nitrogen atoms (28g). Nitrogen percentage = (28/96) × 100 ≈ 29.16%.

Among the practical options provided, Urea maintains the highest concentration of nitrogen, making it the most nitrogen-rich solid fertilizer widely used in agriculture.