Question

Which of the following chemical reactions corresponds to the acid dissociation constant, ka2, for phosphoric acid (H3PO4)?

H3PO4 (aq) + H2O (l) ↔ H2PO4-(aq) + H3O+(aq)

H2PO4-(aq) + H2O (l) ↔ HPO42-(aq) + H3O+(aq)

H2PO4-(aq) + 2 H2O (l) ↔ PO43-(aq) + 2 H3O+(aq)

H2PO4-(aq) + H3O+(aq) ↔ H3PO4 (aq) + H2O (l)

HPO42-(aq) + H2O (l) ↔ PO43-(aq) + H3O+(aq)

PO43-(aq) + H3O+(aq) ↔ HPO42-(aq) + H2O (l)

Answer 1

A was wrong... I think it may be d?

Answer 2

B?
H2PO4-(aq) + H2O (l) ↔ HPO42-(aq) + 1 H3O+(aq)