Chemistry - Naming Ionic Compounds

Question

What is the chemical formula for the compound formed between iron(III) and the bromate ion?

What is the chemical formula for the compound formed between iron(III) and the sulfate ion?

Answer 1

An easy way to find the subscripts is to use the criss cross method.

Fe³⁺ BrO₃^1- criss cross the superscripts to make them subscripts. So 1 goes with Fe and 3 goes with BrO3

Fe(BrO₃)₃ Iron(III) bromate

Fe³⁺ SO₄^2- criss cross the 3 and the 2. So 3 goes with SO4 and 2 goes with Fe

Fe₂(SO₄)₃ Iron(III) sulfate

Answer 2

Hi Angie,

To start off, recall that molecules and compounds that are neutral have net zero charge.

We know that iron(III) is Fe (+3)

Bromate is BrO₃^-, so we will need to have Fe_x(BrO₃)_y, such that x and y give a net neutral compound. We know that Fe is +3, so to balance it, we must have a -3 charge on the anionic part, which results in Fe(BrO₃)₃.

If we look at what sulfate, we know that sulfate is SO₄^2-. Try to balance this one out.

If you do the second one correctly, you should get a fractional unit. However, we want whole numbers for our x and y; therefore, we would multiply by the smallest whole number that can get us there. (Hint: It should be two.)

Hope this helps!

-Winn