Ca(s) + CrO₄^2–(aq) → Cr(OH)₃(s) + Ca²⁺(aq)

oxidation/reduction under basic conditions

[Ca(s) → Ca²⁺(aq) + 2 e^–] × 3

[CrO₄^2–(aq) + 5 H⁺(aq) + 3 e^– → Cr(OH)₃(s) + H₂O(l)] × 2

3 Ca(s) + 2 CrO₄^2–(aq) + 10 H⁺(aq) → 2 Cr(OH)₃(s) + 3 Ca²⁺(aq) + 2 H₂O(l)

10 H₂O(l) → 10 H⁺(aq) + 10 OH^–(aq)

3 Ca(s) + 2 CrO₄^2–(aq) + 8 H₂O(l) → 2 Cr(OH)₃(s) + 3 Ca²⁺(aq) + 10 OH^–(aq)