Question

Calcium sulphide yields the pure hydrogen sulphide gas when heated with dilute:
A.Hydrochloric acid
B.Sodium chloride
C.Nitric acid
D.Nitrous acid

Answer 1

Hint: the calcium sulphide is the chemical compound with the formula $CaS$. This white material crystallizes in the cubes like rock salt. $CaS$ Has been studied as a component in a process that would recycle gypsum, a product of the flue-gas desulfurization.

Complete answer:
As this is a directly opted question from a textbook, this becomes easy to answer,
Now that we know, if iron sulphide is used in the form of a mineral called pyrite, it could contain some impurities of arsenic. So, for the preparation of the arsenic-free hydrogen sulphide the below steps are used
Now as we look into the options in the questions we have to solve for each if we are not clear about the solution. But if we are aware and gone through the textbook we can directly write the following equation that proves that calcium sulphide with which on heating with the dilute yields pure hydrogen gas.
$CaS + 2HCl \to {H_2}S + CaC{l_2}$
Therefore, it is clear that calcium sulphide yields the pure hydrogen gas when treated with dilute hydrochloric acid.

Hence, the right option in this question is (A).

Note: as it was mentioned earlier that it is a direct question from a textbook. Hence it becomes easy as this will be studied in detail. But even though it seems direct, we tend to get confused. So to avoid that we have to note down certain important steps from above, like the equation. It gives us the clear picture on the question and we can proceed. This marks as the easy asked question to the level easy. These kind of questions are what brings us extra credit only when we aware of the concept