Question

A metal forms a compound M2HPO4 .Write the formula of metal nitrate and metal sulphate.

Answer 1

M₂HPO₄
Valency of phosphate ion (PO₄²⁻): 2
There are 2 metal atoms in given molecule
∴ Valency of metal is 1

Valency of
Nitrate: 1
Sulphate: 2

So,
Metal Nitrate: MNO₃
Metal Sulphate: M₂SO₄

Answer 2

Answer: The formula of metal nitrate is $MNO_3$ and metal sulphate is $M_2SO_4$

Explanation: For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.  

Here the metal forms an ionic compound with polyatomic anion $HPO_4^{2-}$ with the formula $M_2HPO_4$. As the valencies of ions are crossed whlie writing the formula, that means the valency of metal is +1.

Thus the metal with valency of +1 combines with nitrate $NO_3^-$ to form $MNO_3$ and combines with sulphate $SO_4^{2-}$ to form $M_2SO_4$.