Question

Assign oxidation numbers to the underlined element in the following species:

H₄P₂O₇

Answer 1

H₄P₂O₇

+1	x	-2
H4	P2	O7

Then, we have

4(+1) + 2(x) + 7(-2) = 0

⇒ 4 + 2x - 14 = 0

⇒ 2x = +10

⇒ x = + 5

Hence, the oxidation number of P is + 5.