Dissolution of potassium and calcium in water equation and ORP.

Both reactions are redox reactions, since the reactions proceed with a change in the oxidation states of the elements that form the molecules of the reacting substances.
1) K (0) + H (+) 2O (2-) => K (+) O (2-) H (+) + H (0) 2;
reducing agent – K (0) -1e -> K (+) | 2 – oxidation;
oxidizing agent – 2H (+) + 2e -> H (0) 2 | 1 – recovery;
2K + 2H2O => 2KOH + H2 ↑.

2) Ca (0) + H (+) 2O (2-) => Ca (2 +) (O (2-) H (+)) 2 + H (0) 2;
reducing agent – Ca (0) -2e -> Ca (2+) | 1 – oxidation;
oxidizing agent – 2H (+) + 2e -> H (0) 2 | 1 – recovery;
Ca + 2H2O => Ca (OH) 2 ↓ + H2 ↑.