To determine the oxidation number of phosphorus in K2HPO4, we first need to understand the oxidation states of the other elements present in the compound.
1. **Potassium (K)** is an alkali metal and has an oxidation number of +1.
2. **Hydrogen (H)** typically has an oxidation number of +1 in compounds.
3. **Oxygen (O)** usually has an oxidation number of -2.
Given the formula K2HPO4, we can calculate the oxidation number of phosphorus (P) as follows:
The compound contains:
- 2 potassium (K) atoms: 2 x +1 = +2
- 1 hydrogen (H) atom: 1 x +1 = +1
- 4 oxygen (O) atoms: 4 x -2 = -8
Now, if we let the oxidation number of phosphorus be represented as x, we can set up the equation for the overall charge of the compound. Since K2HPO4 is neutral, the sum of all oxidation numbers must equal 0:
x + (+2) + (+1) + (-8) = 0
x – 5 = 0
x = +5
Therefore, the oxidation number for phosphorus in K2HPO4 is +5.