Question

What is the oxidation number of phosphorus (P) in phosphoric acid (H3PO4)?

-7
+1
+5
+7

Answer 1

Hey there!:

H is always +1 so the H's have a +3 charge.

O is always -2 so the O's have a -8 charge .

Now, suppose oxidation state for P = X , then :

+3 + X + (-8) = 0 (because of neutral molecule)

x = 8 - 3

x = + 5

So, X = +5 oxidation state.

Answer C

Hope that helps!