Write balanced equations for these reactions using the lowest whole-number coefficients. States of matter are optional:
a. CO₃²⁻ + H₂O → HCO₃⁻ + OH⁻
b. HCO₃⁻ + H₂O → H₂CO₃ + OH⁻
c. H₂CO₃ → CO₂ + H₂O