Question

What is formed when carboxylic acids react with metals and metal carbonates?

Answer 1

Hint: We have to know that the carboxylic acids are those which contain the\[ - {\text{COOH}}\] group as a functional group. Metals are generally electropositive in nature. We should have a basic knowledge that acids react with active metals to liberate hydrogen gas.

Complete answer:
We have to remember that when carboxylic acid reacts with active metals, the products formed are salt and hydrogen gas is liberated. The presence of hydrogen gas can be tested if the burning splinter is brought near the mouth of the test tube, the hydrogen gas will burn with a pop sound.
The following reaction of carboxylic acid i.e acetic acid with metals is shown below:
\[2{\text{C}}{{\text{H}}_3}{\text{COOH}} + {\text{Mg}} \to {\left( {{\text{C}}{{\text{H}}_3}{\text{COO}}} \right)_2}{\text{Mg}} + {{\text{H}}_2}\]
\[2{\text{C}}{{\text{H}}_3}{\text{COOH}} + {\text{Na}} \to {\left( {{\text{C}}{{\text{H}}_3}{\text{COO}}} \right)_2}{\text{Na}} + {{\text{H}}_2}\]
When carboxylic acid reacts with metal carbonates, the products formed are metal carboxylate, carbon dioxide and water. The metal carbonate used in the reaction is sodium carbonate and the acid used is acetic acid.
The following reaction is shown below:
\[2{\text{C}}{{\text{H}}_3}{\text{COOH}} + {\text{N}}{{\text{a}}_2}{\text{C}}{{\text{O}}_3} \to {\text{C}}{{\text{H}}_3}{\text{COONa}} + {{\text{H}}_2}{\text{O}} + {\text{C}}{{\text{O}}_2}\]

Additional information:
Test for hydrogen gas: When a burning candle is brought near the gas, the gas burns with a pop sound. Acetic acid is a common name used for ethanoic acid. Acetic acid is generally a weak acid which undergoes only partial ionization. Acids are those compounds which in its aqueous solution gives hydronium ions i.e \[{{\text{H}}_3}{{\text{O}}^ + }\]. It can also be written as \[{{\text{H}}^ + }\] ions.

Note:
Keep in mind that when acids react with active metals, hydrogen gas is liberated and this hydrogen gas burns with a pop sound when a burning splinter is brought near the mouth of a test tube.