Question 8 — Determine the formula unit mass - Questions at the end of the chapter - Chapter 9 - Atomic Foundations of Matter (Exploration)

Last updated at July 20, 2026 by

Question 8
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.
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  • (i) NH₄NO₃ = 14 + 4 + 14 + 48 = 80 u .
  • (ii) H₃PO₄ = 3 + 31 + 64 = 98 u .
  • (iii) NaHCO₃ = 23 + 1 + 12 + 48 = 84 u .

Atomic masses: H=1, C=12, N=14, O=16, Na=23, P=31.

Formula Unit Masses
NH4NO3 equals 80 u H3PO4 equals 98 u NaHCO3 equals 84 u
Back to: 9.8 Formula Unit Mass of Ionic Compounds
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