Question

The formula of the nitrate of a metal is \( M(NO_3)_2 \). What will be the formula of its phosphate?

• A. \( MPO_4 \)
• B. \( M_2PO_4 \)
• C. \( M_3(PO_4)_2 \)
• D. \( M(PO_4)_2 \)

Hint:

To balance the charges between the metal and phosphate ions, use the cross-multiplication method based on their respective valencies.

Answer 1

The Correct Option is C

The metal in the nitrate has a valency of 2, as indicated by the formula \( M(NO_3)_2 \). For the phosphate, the phosphate ion \( PO_4^{3-} \) has a valency of 3. To balance the charges, we need three \( M^{2+} \) ions for every two \( PO_4^{3-} \) ions. Therefore, the formula of the phosphate will be \( M_3(PO_4)_2 \).