Question

Question 22 Write the empirical formula for at least four ionic compounds that could be formed from the following ions:

Answer 1

Answer:

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

Explanation:

The steps are

1. Write the symbols of the anion and cation.
2. Criss-cross the numbers of the charges to become the subscripts of the other ion.
3. Write the formula with the new subscripts.
4. Divide the subscripts by their highest common factor.
5. Omit all subscripts that are 1.

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.

$\begin{array}{ccc}& \textbf{PO}_{4}^{3-} & \textbf{ClO}_{3}^{-}\\\textbf{NH}_{4}^{+} & \text{(NH _{4} ) _{3} PO _{4} } & \text{NH _{4} ClO}_{3}\\\textbf{Fe}^{3+} & \text{FePO}_{4} & \text{Fe(ClO _{3} )}_{3}\\\end{array}$