Chemistry

The key here is figuring out the charge on the metal $M$ from the phosphate formula. Since $\text{HPO}_4$ is a polyatomic ion with a $-2$ charge (hydrogen phosphate), and it pairs with one $M$ atom in $\text{MHPO}_4$, the metal must be $+2$. Once you know the metal's charge, you can predict what formula its chloride will have—just swap in chloride ions ($\text{Cl}^-$) and balance the charges the same way.

The key here is figuring out the charge on the metal $M$ from the phosphate formula. Since $\text{HPO}_4$ is a polyatomic ion with a $-2$ charge (hydrogen phosphate), and it pairs with one $M$ atom in $\text{MHPO}_4$, the metal must be $+2$. Once you know the metal's charge, you can predict what formula its chloride will have—just swap in chloride ions ($\text{Cl}^-$) and balance the charges the same way.