Question

In alkaline medium $Cl{O_2}$ oxidizes to ${H_2}{O_2}$ and ${O_2}$ and itself gets reduced to $C{l^ - }$ . How many moles of ${H_2}{O_2}$ are oxidized by $1$ mole of $Cl{O_2}$ ?
(A) $1$
(B) $1.5$
(C) $2.5$
(D) $3.5$
(E) $5$

Answer 1

The laws of chemical combination indicate the need to balance the chemical equations in such a manner that the number of atoms of each element remain same on the reactant as well as the product side which ensures that the total mass of reactants and the total mass of products remains unchanged and equal.

Complete answer:
The chemical reactions follow the laws of chemical combination and one of these laws known as the law of definite proportion states that the atoms combine to form molecules only in specific proportions. Another such law is called the law of Conservation of mass that states that the mass remains conserved throughout the reaction. This means that no new element can be formed in a chemical reaction. Thus the atoms of each element are only present in a fixed amount and the reaction only causes a rearrangement of atoms.
The balanced chemical reaction involving $Cl{O_2}$ can be written as follows:
$2Cl{O_2} + 5{H_2}{O_2} + 2O{H^ - } \to 2C{l^ - } + 5{O_2} + 6{H_2}O$
The equation suggests that $Cl{O_2}$ acts as an oxidizing agent and the $O{H^ - }$ ions are used in the reaction to provide an alkaline medium. $Cl{O_2}$ itself reduces to chloride ions.
The moles of products produced and the reactants consumed in a reaction can be calculated by keeping the ratio of stoichiometric coefficients of a balanced chemical equation in mind.
Thus, two moles of $Cl{O_2}$ react with five moles of hydrogen peroxide and produce five moles of oxygen. When dealing with one mole of $Cl{O_2}$ , half the number of hydrogen peroxide molecules react and half the number of oxygen molecules are produced.
Therefore, one mole of $Cl{O_2}$ oxidizes $2.5$ moles of ${H_2}{O_2}$ to give the same number of moles of oxygen.
The correct option is (c).

Note:
The process of oxidation involves the loss of electrons and reduction involves acceptance of electrons. The chemical agent that itself gets reduced but facilitates the oxidation of another reactant is called the oxidizing agent.