Question

Hydrogen is a good reducing agent.
What do you understand by the above statement?

Answer 1

Reducing agents is the compound or element that loses an electron and reduces the subsequent reactant. In this process, the reducing agent is oxidized. A good reducing agent will lose an electron easily to expel the oxygen from the compound.

Complete answer:
The basic definition of Reduction is formed across hydrogen which is if a compound gains hydrogen and loses oxygen it is said to be reduced.
Hydrogen as we know is an element with only one electron and one proton. When hydrogen acts as a reducing agent it loses one electron to form $H^+$. The lost electron is gained by one of the reactants/compounds. This means that the compound is reduced by hydrogen. Hydrogen acts as an electron donor.
There are many reducing agents such as $H_2$, Li, CO, Fe, Zn, etc. Out of them, hydrogen is said to be a good reducing agent because when hydrogen reacts with metallic oxides of iron, copper, zinc, lead, etc. it removes the oxygen present in the metallic oxides. The removal of oxygen from the metallic oxides means that they are reduced to their corresponding metal.
It is one of the most common ways of extraction. The hydrogen gas is passed over hot metal oxides to reduce the latter to a metal.
Let us look at an example of Copper oxide.
When hydrogen gas passes over copper oxide, the copper oxide is reduced as it gains an electron and the oxygen is removed from it. It results in the formation of Copper metal and oxygen is liberated.
$CuO\text{ + }{{\text{H}}_{2}}\text{ }\to \text{ Cu + }{{\text{O}}_{2}}$
Therefore, Hydrogen is said to be a good reducing agent.

Note:
Do not confuse what happens during oxidation and reduction. In simple words- a reducing agent reduces the other compound by giving an electron and itself gets oxidized by losing an electron. Similarly, an oxidizing agent oxidizes the other compound by taking an electron and itself gets reduced by accepting an electron.