Separate samples of a solution of an unknown soluble ionic compound are treated with kcl, na2so4, and naoh. a precipitate forms only when na2so4 is added. which cations could be present in the unknown soluble ionic compound?

Ba⁺², Sr⁺², Ca⁺², and Ra⁺²

Explanation:

If a precipitate is formed, then the ionic compound (a salt or a base) will not be soluble in water. That compound is formed by a metal cation and the anions of the substances given: Cl⁻, SO₄⁻² and OH⁻. With Cl⁻ and SO₄⁻² it will form a salt, and with OH⁻ it will form a base.

The insoluble substance is formed only with SO₄⁻², and most compounds formed with this anion are soluble, the exceptions are the cations Ba⁺², Sr⁺², Ca⁺², Ra⁺², and Pb⁺². The salt formed between Pb⁺² and Cl⁻ is also insoluble, so, Pb⁺² can't be one of the cations.

The soluble base is the ones formed by metals from the groups I and II, all the others are insoluble and would form a precipitated. Ba, Sr, Ca and Ra are from group 2, so they form soluble bases.

Then, the possible cations are: Ba⁺², Sr⁺², Ca⁺², and Ra⁺².

a corroding iron, if that's one of your choices

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.