# Question #20e6a

##### 1 Answer

Here's what I got.

#### Explanation:

Start with what you know for sure, which is that oxygen has an oxidation number of

Remember that the sum of the oxidation numbers of *each atom* that is part of a compound **must be equal** to the **net charge** of said compound.

For water, you will have

#"H"_ 2 stackrel(color(blue)(-2))("O")#

Since you have **each** of them to get

#2 xx (+1) + 1 xx (-2) = 0#

Therefore, you will have

#stackrel(color(blue)(+1))("H")_ 2 stackrel(color(blue)(-2))("O")#

Do the same for sulfur dioxide. You will have

#"S" stackrel(color(blue)(-2))("O")_2#

Since you have

#1 xx (+4) + 2 xx (-2) = 0#

Therefore, you will have

#stackrel(color(blue)(+4))("S")stackrel(color(blue)(-2))("O")_2#

Finally, move on to the *permanganate ion*,

#"Mn" stackrel(color(blue)(-2))("O") _4""^(-)#

This time, the ion sum of the oxidation numbers must be equal to

#1 xx (+7) + 4 xx (-2) = -1#

Therefore, you will have

#stackrel(color(blue)(+7))("Mn") stackrel(color(blue)(-2))("O") _4""^(-)#