Final answer:
The oxidation state of phosphorus in H3PO3 is +3.
Step-by-step explanation:
The oxidation state of phosphorus in H3PO3 can be determined by assigning oxidation states to the other elements in the compound. In H3PO3, hydrogen (H) always has an oxidation state of +1 (Rule 3), and oxygen (O) usually has an oxidation state of -2 (Rule 4).
Since the overall charge of the compound is 0, the sum of the oxidation states of all elements must equal 0.
The compound has a total of 3 hydrogen atoms, each with an oxidation state of +1. The oxidation state of oxygen can be calculated as (-2) x (number of oxygen atoms) = (-2) x (2) = -4.
Using the sum of the oxidation states rule, we can calculate the oxidation state of phosphorus: (+1 x 3) + (-4) + oxidation state of phosphorus = 0. Solving for the oxidation state of phosphorus, we find that it is +3.