Question

an acid (x) reacts with a base (y) to produce mg₃(po₄)₂. what are x and y?
○ x = h₃po₃; y = mg(oh)₂
○ x = h₃po₄; y = mg(oh)₂
○ x = h₃po₄; y = ca(oh)₂
○ x = h₃po₃; y = ca(oh)₂

Explanation:

1. Recall the reaction of acid and base (neutralization): Acid + Base → Salt + Water. The salt here is \( \ce{Mg3(PO4)2} \), so we need an acid providing \( \ce{PO4^{3-}} \) and a base providing \( \ce{Mg^{2+}} \).
2. Analyze the acid: To form \( \ce{PO4^{3-}} \) in the salt, the acid should be phosphoric acid (\( \ce{H3PO4} \)) (since \( \ce{H3PO3} \) gives \( \ce{PO3^{3-}} \), not \( \ce{PO4^{3-}} \)).
3. Analyze the base: To form \( \ce{Mg^{2+}} \) in the salt, the base should contain \( \ce{Mg^{2+}} \), so \( \ce{Mg(OH)2} \) (not \( \ce{Ca(OH)2} \), which would give \( \ce{Ca^{2+}} \) leading to a different salt like \( \ce{Ca3(PO4)2} \)).
4. Check the reaction: \( 2\ce{H3PO4} + 3\ce{Mg(OH)2}

ightarrow \ce{Mg3(PO4)2} + 6\ce{H2O} \), which produces the required salt.

Answer:

B. \( X = \ce{H3PO4} \), \( Y = \ce{Mg(OH)2} \)