Final answer:
One of the ions forming compound A, which is likely magnesium phosphate (Mg3(PO4)2), in the reaction between magnesium hydroxide and phosphoric acid, is either Mg2+ or PO43-. Mg2+ comes from the dissociation of Mg(OH)2, and PO43- comes from the dissociation of H3PO4.
Step-by-step explanation:
The reaction presented is 3 Mg(OH)2 + 2 H3PO4 → compound A + H2O, and it involves the formation of a compound from magnesium hydroxide (Mg(OH)2) and phosphoric acid (H3PO4). To identify one of the ions that form compound A, we look into the dissociation reactions:
- Mg(OH)2 (s) ⇒ Mg2+ (aq) + 2OH- (aq)
- H3PO4 ⇒ 3H+ (aq) + PO43- (aq)
From these dissociation reactions, we can determine that Mg2+ and PO43- are the ions involved in forming compound A, which is likely Mg3(PO4)2, magnesium phosphate. The other possible ion, OH-, comes from the dissociation of Mg(OH)2, which is a weak base and somewhat insoluble in water, meaning it will not contribute significantly to the formation of compound A compared to the ions from the fully dissociated H3PO4.