How many atoms of oxygen are in one formula unit of Al_2(SO_4)3Al2(SO4)3?

1 Answer
anor277
May 10, 2016

Well, clearly there are 12. Why?

Explanation:

Al_2(SO_4)_3Al2(SO4)3 formally derives from an aluminum trication, Al^(3+)Al3+, and a sulfate dianion, SO_4^(2-)SO2−4. Now ionic substances form to balance charges, and the only way to achieve neutrality for these net charges is to take 6 positive charges, i.e. (2xxAl^(3+))(2×Al3+), and 6 negative charges (3xxSO_4^(2-))(3×SO2−4).

If you count up all the atoms that carry these charges, there are (2xxAl+3xxS+3xx4xxO)(2×Al+3×S+3×4×O). Is this clear?

How would I form a salt from Ca^(2+)Ca2+ and phosphate anion, PO_4^(3-)PO3−4? What composition would give electrical neutrality?

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