16) Chemical equation: Ca + H₃PO₄ → Ca₃(PO₄)₂ + H₂.
Oxidation reaction: Ca⁰ → Ca⁺² + 2e⁻ /×3.
3Ca⁰ → 3Ca⁺² + 6e⁻
Reduction reaction: 6e⁻ + 2H₃⁺¹ → 3H₂⁰.
Calcium change oxidation number from 0 to +2 (oxidation) and hydrogen change oxidation number from +1 to 0 (reduction).
Balanced chemical equation: 3Ca + 2H₃PO₄ → Ca₃(PO₄)₂ + 3H₂.
Calcium is stronger reducing agent than hydrogen, gives electrons easier.
This is example of single displacement reaction.
Single displacement is reaction where neutral element metal or nonmetal become an ion as it replaces another ion in a compound.
17) Balanced chemical equation:
3Ca(s) + 2H₃PO₄(aq) → Ca₃(PO₄)₂(aq) + 3H₂(g).
Ionic equation: 3Ca + 6H⁺ + 2PO₄³⁻ → 3Ca²⁺ + 2PO₄³⁻ + 3H₂.
Net ionic equation: 3Ca + 6H⁺ → 3Ca²⁺ + 3H₂.
A spectator ion is an ion that exists as a reactant and a product in a chemical equation.
A spectator ion is phospate anion PO₄³⁻.
