Na₂C₂O₄ (sodium oxalate) a. What is the oxidation number of sodium in sodium oxalate? b. What is the oxidation number of carbon in sodium oxalate? c. What is the oxidation number of oxygen in sodium oxalate?
The Correct Answer and Explanation is:
To determine the oxidation numbers of sodium, carbon, and oxygen in sodium oxalate (Na₂C₂O₄), we need to follow basic rules for oxidation states.
a. Oxidation number of sodium in sodium oxalate:
Sodium (Na) is an alkali metal, and alkali metals always have an oxidation number of +1 in their compounds. Therefore, the oxidation number of sodium in Na₂C₂O₄ is +1.
b. Oxidation number of carbon in sodium oxalate:
In sodium oxalate, the oxalate ion is the central structure, which is C₂O₄²⁻. To find the oxidation number of carbon, we first need to consider the overall charge of the ion (C₂O₄²⁻) and the oxidation states of oxygen.
Each oxygen atom in oxalate typically has an oxidation number of -2. Since there are four oxygen atoms, their total contribution to the charge is 4 × (-2) = -8.
Now, the overall charge of the oxalate ion is -2, so the sum of the oxidation numbers of the two carbon atoms must balance the -8 from oxygen to make the total charge -2. Therefore, we can set up the following equation:
2 × (oxidation number of carbon) + (-8) = -2
Solving for the oxidation number of carbon:
2 × (oxidation number of carbon) = 6
The oxidation number of each carbon atom is +3.
c. Oxidation number of oxygen in sodium oxalate:
As mentioned earlier, oxygen generally has an oxidation number of -2 in most of its compounds, except in peroxides or with fluorine. In sodium oxalate, the oxygen atoms are part of the oxalate ion (C₂O₄²⁻), and thus, the oxidation number of oxygen remains -2.
Summary:
- The oxidation number of sodium is +1.
- The oxidation number of carbon is +3.
- The oxidation number of oxygen is -2.
