Question

The electrolysis of acidified water is an example of:
(A) Reduction
(B) Oxidation
(C) Redox reaction
(D) Synthesis

Answer 1

Hint: The water containing a small amount of acid dissolved in it is called acidified water. And we can say that the chemical decomposition produced by passing electric current through a solution containing ions is called electrolysis. Redox reaction is a reaction where both oxidation and reduction takes place.

Complete-step- by- step answer:
As we know that water is a very poor conductor of electricity, but it has some hydrogen ions and hydroxide ions. These ions are formed when a small proportion of water molecules naturally dissociate. If water is acidified with a little amount of dilute sulphuric acid, then following process occurs:
Ions are attracted to the cathode, gain electrons and form hydrogen gas.
                                         \[\begin{align}
                                        & {{H}^{+}}+{{e}^{-}}\to H \\
                                        & H+H\to {{H}_{2}} \\
                                         \end{align}\]

Ions are attracted to the anode, loose electrons and form oxygen gas.
                                         \[\begin{align}
                                        & O{{H}^{-}}\to OH+{{e}^{-}} \\
                                        & OH+OH\to {{H}_{2}}O+O \\
                                        & O+O\to {{O}_{2}}\uparrow \\
                                         \end{align}\]
The overall balanced reaction for the process can be written as:

\[\begin{align}
  & 2{{H}_{2}}O\left( l \right)\to 2{{H}_{2}}\left( g \right)+{{O}_{2}}\left( g \right) \\
 & \\
\end{align}\]
Here we can say that the electrolyte is dilute sulphuric acid which, during electrolysis is split into hydrogen and oxygen gases. Theoretically into a 2:1 ratio by gas volume. Or in simple words, we can say that the volume of hydrogen given off is twice the volume of oxygen given off.

So, the correct option is (C), that is it is an example of redox reaction.

Additional Information:
As we have discussed about the most familiar example of electrolysis of decomposition of water into hydrogen and oxygen by means of electric current. In some way the same process can be used to decompose compounds other than water.
It is also found that sodium, chlorine, magnesium, and aluminium are four elements that are produced commercially by the process of electrolysis.

Note: At cathode, cations are attracted, gain electrons and form hydrogen gas. And anions are attracted to the anode, loose electrons and form oxygen gas. Here is an important thing to note is that the volume of hydrogen gas given off is more than that of oxygen gas.