Question

Metals react with acids and produce _________ gas.

Answer 1

Try to understand the role of mineral acid in the above reaction. They are used as a protonating agent as they release hydrogen ions in aqueous solution. To solve the question, take a simple metal, say zinc and write its reaction with an acid like sulphuric acid. The above reaction is a redox reaction i.e. one atom gets oxidized and another atom will be reduced.

Complete step-by-step answer:
Metals are good reducing agents as they easily get oxidised. This is because they have electrons which can be easily released.
The hydrogen ions in the aqueous solution of the acid accept these electrons and hence get reduced. This leads to the formation of molecular hydrogen.
We will now consider a metal, let's say zinc. We will now write its reaction with a strong mineral acid like sulphuric acid.
$Z{{n}_{(s)}}+{{H}_{2}}S{{O}_{4}}\to \text{ }Z{{n}^{2+}}+S{{O}_{4}}^{2-}+{{H}_{2\uparrow }}$
The reaction given above is a redox reaction i.e. oxidation and reduction takes place simultaneously in a single reaction.
Therefore, from the above reaction we can conclude that the gas released is hydrogen.

The correct answer is option (D).

Note: The reaction of metals with acids is a standard reaction to check the presence of metal in a given solution. However, some metals react with bases as well and release hydrogen gas. These metals are called amphoteric metals. Examples of some amphoteric metals are zinc, aluminium etc. The reaction between zinc and a base( in this case sodium hydroxide) is given below:
$Z{{n}_{(s)}}+2NaOH\to \text{ }N{{a}_{2}}Zn{{O}_{2}}+{{H}_{2}}$