1. Assign Oxidation Numbers

* K (Potassium): +1 in all compounds (alkali metals always have +1)

* O (Oxygen): -2 in all compounds (except peroxides)

* H (Hydrogen): +1 in all compounds (except metal hydrides)

* P (Phosphorus): We need to calculate this.

2. Calculate the Oxidation Number of Phosphorus

* In H3PO4:

* 3(+1) + x + 4(-2) = 0 (The sum of oxidation numbers in a neutral compound is 0)

* x = +5

* In K3PO4:

* 3(+1) + x + 4(-2) = 0

* x = +5

3. Analyze the Changes

* Potassium (K) and Oxygen (O) maintain the same oxidation numbers throughout the reaction.

* Phosphorus (P) remains at +5 in both H3PO4 and K3PO4.

Conclusion:

No element increases its oxidation number in this reaction. The oxidation number of phosphorus remains constant.