Question

Insoluble base reacts dilute acid with:
A. soluble salt + water
B. insoluble salt + acid
C. insoluble salt + base
D. soluble salt

Answer 1

Hint: The answer lies in the fact that reaction of insoluble or soluble reactant with acid can make soluble salts. Here we do titration and titration is only done for one case. The insoluble reactant used here is a base which may be metal oxide or metal carbonate.

Complete Solution :
We have studied about the acid – base reactions in our lower classes of chemistry. We have also studied that when acid and base react together they form salt along with by-products. When an insoluble base or reactants reacts with acid they also form salt but the salts are soluble in nature.
- Soluble salts are prepared when we treat an acid with a suitable insoluble reactant .The insoluble reactant (base) used here may be a metal oxide, a carbonate, or only a metal.
- The insoluble base used here depends upon the particular salt that is required.
- For example, if we have to make copper salt then we have to use copper oxide or carbonate to react with dilute acids only copper metal does not form copper salts with dilute acids. Flammable hydrogen is produced when we react with metal and acid.
- To make the soluble salt from the acids and insoluble base dilute acid is added to the container and then a powdered insoluble base is added in it which produces effervescence.
- After that filter the mixture to remove the excess powdered and then leave the solution so that the water in it can evaporate to obtain the pure salt.
Filtering is done as it removes the entire unreacted insoluble base from the solution.
So, after filtering, all the insoluble reactants are removed and leave only soluble salt and water and then the evaporation of water leaves behind only the pure salt. The reaction taking place is,
\[CuO+{{H}_{2}}S{{O}_{4}}\to CuS{{O}_{4}}+{{H}_{2}}O\]
Hence, water and soluble salts are formed when an insoluble base reacts with dilute acid.
So, the correct answer is “Option A”.

Note: All insoluble types of reactants (metals) do not react with dilute acid. The name of the salts depends upon both the acid and base. If we have taken Sulphuric acid reacting with Copper oxide then the salt formed is called a Copper sulphate.