Question

When a base combine with metal it forms metal salt/base and release:
(a)- Oxygen
(b)- Hydrogen
(c)- Carbon dioxide
(d)- Nitrogen

Answer 1

Hint: The strength of the base to combine with a metal must be strong like sodium hydroxide (NaOH), only then the reaction will occur. The gas releases in this reaction have a pop sound and with this sound, we can identify the gas.

Complete answer:
Metals are those elements that are present on the left side of the periodic table. Mostly the metals belong to group 1 (alkali metals) and group 2 (alkaline earth metals). There are many properties of metals like electropositive nature, malleable, ductile, heat conductivity, electricity conductivity; their oxides are basic, etc.
Since the metals have basic nature, they do not react with the base. A base is a compound that can either have an ionizable hydroxyl ion or has the ability to accept a proton.
But if the strength of the base is very strong, then its reaction with a metal can occur. So, a base like sodium hydroxide (NaOH) can be used to react with a metal.
So, when a strong base like (NaOH) reacts with a metal, there is the formation of metal salt/base and gas which makes a pop sound. This pop sound is the characteristic of the evolution of hydrogen gas. Therefore, the gas that evolved in the reaction is hydrogen gas.

Hence, the correct answer is an option (b)- Hydrogen.

Note:
If we use a weak base to react with metal then the reaction will not occur. The metal in the reaction will be in the elemental form. The pop sound can be identified when the burning candle is brought near the test tube.