half yearly exam questions – atomic foundations of matter – Discussion Forum

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Virat

Asked: September 9, 2026In: Class 9 Science

Determine the formula unit mass of the following substances. (i) Ammonium nitrate (NH4NO3), used as a nitrogen fertiliser, which is essential for plant growth. (ii) Phosphoric acid (H3PO4), used to make phosphate fertiliser and detergents. (iii) Sodium hydrogencarbonate (NaHCO3), used to relieve acidity and helps in digestion.

The calculated formula unit masses are 80 u for ammonium nitrate NH4NO3, 98 u for phosphoric acid H3PO4 and 84 u for sodium hydrogencarbonate NaHCO3, found by adding the individual atomic masses.