1. P₂O₅ → oxidation number of phosphorous is +5 and Oxygen is -2.
2. (SO₄)²⁻ → oxidation number of sulfur is +6 and Oxygen is -2.
3. KClO₃ → oxidation number of Potassium is +1, Chlorine is +5, and Oxygen is -2.
4. NH₄Cl → oxidation number of Nitrogen is -3, Hydrogen is +1, and Chlorine is -1
5. (NH₄)₂S → oxidation number of Nitrogen is -3, Hydrogen is +1, and Sulfur is -2
Explanation:
General Rules for assigning oxidation numbers
The oxidation number of a free element is always 0.
The oxidation number of a mono-atomic ion equals the charge of the ion.
The alkali metals (group I) always have an oxidation number of +1.
The alkaline earth metals (group II) are always assigned an oxidation number of +2.
Oxygen almost always has an oxidation number of -2, except in peroxides (H₂O₂) where it is -1 and in compounds with fluorine (OF₂) where it is +2.
Hydrogen has an oxidation number of +1 when combined with non-metals, but it has an oxidation number of -1 when combined with metals.
The algebraic sum of the oxidation numbers of elements in a compound is zero.
The algebraic sum of the oxidation states in an ion is equal to the charge on the ion.
Using the above rules:
1. P₂O₅
∵ it is a neutral compound its total charge is 0.
Also, we know that oxygen has an oxidation number of -2.
Let oxidation number of P be x
∴ 2(x)+5(-2)=0 → 2x=+10 → x=+5
∴oxidation number of phosphorous is +5.
2. SO₄²⁻:
∵ it is a charged ion its total charge is -2.
Also, we know that oxygen has an oxidation number of -2.
Let oxidation number of S be x
∴ (x)+4(-2)= -2 → x=+6
∴oxidation number of sulfur is +6.
3. KClO₃:
∵ it is a neutral compound its total charge is 0.
Also, we know that oxygen has an oxidation number of -2 and the oxidation number of K (group I) is +1
Let oxidation number of Cl be x
∴ (+1) + (x) + 3(-2) = 0 → x=+5
∴oxidation number of Chlorine is +5.
4. NH₄Cl:
∵ it is a neutral compound its total charge is 0.
Also, we know that chloride has an oxidation number of -1
Hydrogen has an oxidation number of +1 when combined with non-metals
Let oxidation number of N be x
∴ (x) + 4(+1) + (-1) = 0 → x=-3
∴oxidation number of Nitrogen is -3.
5. (NH₄)₂S:
∵ it is a neutral compound its total charge is 0.
Also, we know that chloride has an oxidation number of -1
Ammonium ion (NH₄⁺) has an oxidation number of +1
Let oxidation number of N be x
∴ 2(+1) + (x) = 0 → x= -2
∴oxidation number of sulfur is -2.
