Question

When sodium reacts with excess of oxygen. oxidation number of oxygen changes from

• A. $0$ to $-1$
• B. $0$ to $-2$
• C. $-1$ to $-2$
• D. $+1$ to $-1$

Answer 1

The correct option is A $0$ to $-1$

When sodium reacts with excess of oxygen, it leads to the formation of sodium peroxide.

$2Na+O_2\to N{a}_2{O}_2$

Hence there is a change in oxidation state from 0 to -1.