Can someone please check-over my answers to these Chemistry problems?

Question

What are the oxidation numbers of K, Cl, and O in KClO₃?

A. K = +2, Cl = +4 and O = –2

B. K = +1, Cl = +5 and O = –2

C. K = +3, Cl = +3 and O = –2

D. K = +1, Cl = –5 and O = –2

E. None of the Above

What is the oxidation number of O in PO₄^3–?

A. 0

B. –1

C. –2

D. –3

E. None of the Above

What are the oxidation numbers of P and H in PH₄⁺?

A. P = +3 and H = –1

B. P = –3 and H = +1

C. P = –2 and H = +1

D. P = –1 and H = +1

E. P = +1 and H = –1

Answer 1

Hi Jesset. Your answers are correct. You can use algebra to solve these.

For KClO_3,. K has a charge of +1, therefore the ClO₃ ion has a negative charge.  Oxygen always has a -2 charge (with a couple exceptions).

K + Cl + 3(O) = 0

+1 + Cl + 3(-2) = 0

1 + Cl -6 = 0

Cl – 5 = 0

Cl = 5

For the PO₄^3– ion, oxygen always has a -2 charge (with a couple of exceptions).

 For the PH₄⁺ ion, H has a positive charge therefore P has a charge of -3.