Question 22 write the empirical formula for at least four ionic compounds that could be formed from the following ions:
(a) po4^3-,
(b) nh4^+,
(c) fe^3+,
(d) clo3^-

Empirical formula is the chemical formula of the simplest ratio of the number of atoms of each element present in a compound. Ionic compounds is formed when the complete transfer of electrons takes place from one element (usually metals) or group of atoms (polyatomic positive ions) to another element (usually non-metals) or group of atoms (polyatomic negative ions).

To form the ionic compounds of the given ions, we must combine a positive and a negative ion together.

Thus, the ionic compounds formed are

Learn more about ionic compounds here: link

We can use the criss-cross method to work out the formulas.  

Explanation:

The steps are

When we use this method, the formula for the compound formed from NH₄⁺ and PO₄³⁻ becomes (NH₄)₃PO₄.

The table below lists the formulas for the possible combinations.

the dependant variable is spilled water

the independent is the heat