Question

Metal carbonates react with dilute ${H_2}S{O_4}$ to produce:
A.Carbonic acids
B.Metallic oxides
C.Weak metallic oxides
D.$C{O_2}$ gas

Answer 1

Hint: We know that all metal carbonates are weak bases. In addition to dilute acid, a neutralization reaction takes place between the acid and base, which will result in the formation of salt and water. Comparing the reaction of metal carbonate and ${H_2}S{O_4}$ to a standard acid base reaction, we will get the products formed.

Complete step by step solution:
When an acid is reacted to a metal carbonate, a salt and water must be formed given the knowledge we have about acid base neutralization reactions. But in case of metal carbonates, we also observe the formation of a gas. The carbonate ion being unstable undergoes decomposition forming carbon dioxide gas. The production of the gas is detected by effervescence (bubbling) in the solution. It can also be tested by passing the gas formed through lime water turning the latter milky.
The overall products of the reaction of metal carbonates with dilute ${H_2}S{O_4}$ results in the formation of the metal sulphate, water and carbon dioxide gas.
The reaction can be represented as follows: $MC{O_3} + {H_2}S{O_4} \to MS{O_4} + C{O_2} + {H_2}O$
Where M is any suitable metal.

Thus, the correct answer is D.

Additional Information:
Carbonic acids are obtained in the reaction of metal hydrogen carbonates with dilute acid. The bicarbonate ion takes up hydrogen ions from the acid forming carbonic acid or hydrogen carbonate. However, the carbonic acid being unstable breaks down giving carbon dioxide and water.

Note:
Metal carbonates are basic in nature and their aqueous solutions are strongly alkaline. Since they release carbon dioxide gas which is easy to detect on reaction with acids, they can be used to check whether a compound is acidic or not.