Question

In the reaction $2Ba{O_2} \to 2BaO + {O_2}$, the oxidation number of Barium
A. Decreases from +4 to +2
B. Decreases from +2 to 0
C. Increases from +4 to -2
D. Does not change

Answer 1

For solving this question, first we need to understand the concept of oxidation number. The oxidation state, sometimes referred to as oxidation number, describes the degree of oxidation of an atom in a chemical compound.

Complete answer:
For the calculation of oxidation number we need to keep in mind the following things:
The oxidation number of a free element is always 0.
The oxidation number of a monatomic ion equals the charge of the ion.
The oxidation number of H is +1, but it is -1 in when combined with less electronegative elements.
The oxidation number of O in compounds is usually -2, but it is -1 in peroxides.
Now, we will consider the equation mentioned in the question:
$2Ba{O_2} \to 2BaO + {O_2}$
Here, we need to determine the oxidation number of Ba so we will write it in the reaction.
$2Ba{O_2} \to 2BaO + {O_2}$
From this reaction, the oxidation state of barium remains the same. It means that the oxidation number of Barium remains +2 throughout the reaction. Thus, the oxidation number of oxygen changes. In barium peroxide, it is −1, and in barium oxide, it is −2 and in oxygen, it is 0.
Therefore, the option D is correct.

Note:
With the help of oxidation numbers, chemists can keep track of electrons within a given compound. Also, we can use the guidelines to assign oxidation numbers to atoms in a compound. The change in oxidation state during a reaction tells us that there is a transfer of electrons.