Question

What salts does calcium form with sulphide dianion, and with hydrogen sulphide anion?

Answer 1

Hint: We know that anions are negative and Sulphur has a valency of 2. So it forms a Sulphide dianion that is $ {{S}^{-2}} $ . Hydrogen sulphide ( $ {{H}_{2}}S $ ) forms $ {{H}^{+}} $ cation and $ {{S}^{-2}} $ anion. So, Calcium will react with sulphide dianion, and with hydrogen sulphide anion to form two different products.

Complete Step By Step Answer:
Calcium forms $ C{{a}^{+2}} $ ion to combine with $ {{S}^{-2}} $ i.e. Sulphide dianion. When calcium reacts with $ {{S}^{-2}} $ it forms calcium sulphide. The di positive charge of calcium requires two negative charges to cancel out and form a neutral salt. Thus it forms calcium sulphide as the product.
$ C{{a}^{+2}}\text{ + }{{\text{S}}^{-2}}\text{ }\to \text{ Ca}{{\text{S}}_{(s)}} $
Now, the Hydrogen Sulphide anion is represented as $ H{{S}^{-}} $ .
So lets the reaction between $ C{{a}^{+2}} $ and $ H{{S}^{-}} $ (hydrogen sulphide anion) which results in the formation of calcium hydrogen sulphide. Calcium has 2 positive charges and hydrogen sulphide anion has one negative charge. So, it cannot be neutralized completely.
$ C{{a}^{+2}}\text{ + H}{{\text{S}}^{-}}\text{ }\to \text{ Ca}{{\left( HS \right)}_{2}} $
Ca has a valency of 2 and hydrogen sulphide anion has a valency of 1. Hence, calcium hydrogen sulphide has the formula $ \text{Ca}{{\left( HS \right)}_{2}} $ .
Final answer: Therefore, calcium forms Calcium sulphide salt with sulphide dianion and Calcium hydrogen sulphide salt with hydrogen sulphide anion.

Note:
$ {{H}_{2}}S $ can form two salts. One could be $ {{S}^{-2}} $ and the other one could be hydrogen sulphide $ H{{S}^{-}} $ . So, we can relate both the above chemical reactions with the reaction with hydrogen sulphide salts. The overall reaction with both the salts would be the same as the one with sulphide dianion and hydrogen sulphide anion. Also, remember salts are produced when an acid and base react or an anion or cation come together.