Calculation of formula mass of Potassium Chlorate, baking soda, Ammonium nitrate and urea

Self-Assessment Exercise 1.4: 1. Potassium Chlorate (KClO₃) used commonly for the laboratory preparation of oxygen gas (O₃). Calculate its formula mass.

2. When baking soda, NaHCO_₃ is heated, carbon dioxide is released, which is responsible for the rising of cookies and bread. Determine the formula masses of baking soda and carbon dioxide.

3. Following compounds are used as fertilizers. Determine their formula masses. (i) Urea, (NH₂)_₂CO (ii) Ammonium nitrate, NH4NO₃

Solution

1. Formula mass of KClO₃ = 1 × Atomic mass of K + 1 × Atomic mass of Cl + 3× Atomic mass of O

= 1 × 39 + 1 × 35.5 + 3 × 16

= 122.5 amu

2. Formula mass of NaHCO₃ = 1× Atomic mass of Na + 1 × Atomic mass of H + 1 × Atomic mass of C + 3 × Atomic mass of O

= 1 × 23 +1 ×1 + 1 ×12 + 3×16

= 23 + 1+ 12+ 48

= 84 amu

3. (i) Formula mass of Urea (NH₂)₂CO = 2 ( Atomic mass of N + 2 × Atomic mass of H) + 1× Atomic mass of C + Atomic mass of O

= 2 (14+ 2 × 1) + 1 × 12 + 16

= 2 (16) +12 +16

= 32 + 28

= 60 amu

(ii) Formula mass of NH₄NO₃ or N2H₄O₃ = 2 (Atomic mass of N)+ 4 × Atomic mass of H + 3× Atomic mass of O

= 2 (14) + 4 × 1 + 3 × 16

= 28 + 4+ 48

= 80 amu

Representative Particles of Elements and Compounds

The term that represents the species present in a substance is called representative particles.

For examples, the term atoms, molecules and formula units are used to represent the particles of element, molecular compound and ionic compound. So, these terms are representative particles of elements, molecular compound and ionic compounds, respectively.

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