The Student Room Group

Slightly confused by oxidation states/rules....

So....

The sum of the oxidation states of all the atoms or ions in a neutral compound is zero.

However, I also read that:

The sum of the oxidation states of all the atoms in an ion is equal to the charge on the ion

Let us say then we have the ionic compound Hydrochloric acid.

HCL

H = 1 and CL = -1 so together they give us 0. That satisfies the 1st rule and would also satisfy the 2nd rule because the overall charge of the ion is 0?

Am I intrepreting/applying the rules correctly?

Scroll to see replies

Yeah, it's right.

Could you work out the oxidation states of each atom in SO42-?
Reply 2
Original post by Serine Soul
Yeah, it's right.

Could you work out the oxidation states of each atom in SO42-?


SO42-

Formatting is key.
Original post by alow
SO42-

Formatting is key.

How do you do that? :colondollar:
Reply 4
Original post by apronedsamurai
So....

The sum of the oxidation states of all the atoms or ions in a neutral compound is zero.

However, I also read that:

The sum of the oxidation states of all the atoms in an ion is equal to the charge on the ion

Let us say then we have the ionic compound Hydrochloric acid.

HCL

H = 1 and CL = -1 so together they give us 0. That satisfies the 1st rule and would also satisfy the 2nd rule because the overall charge of the ion is 0?

Am I intrepreting/applying the rules correctly?


yuppp
but sometimes they change like
Fe in Fe2O3 has oxidation state of 3+
and in FeO it has an oxidation state of 2+
I think this is true for all transition metals.
Reply 5
Original post by Serine Soul
How do you do that? :colondollar:


click advanced and it'll come up with formatting options
clicking X2 = subscript and X2 = superscript
Reply 6
Original post by z33
click advanced and it'll come up with formatting options
clicking X2 = subscript and X2 = superscript


Ok, so I am getting a little confused by the half equations/oxidation numbers....

HNO3(aq) + H3AsO3 NO(g) + H3AsO4(aq) + H2O(l)

HNO3(aq) H =1 N = 5 and O = -6 (Because 3x-2) and -6+5+1 =0

H3AsO3 H=3 (3x1) As=5 (Because group 5) and O = -6 (3x2)

But that means 3+-6+5=+2....? :|

Or should it be H =3 O =-6 and As =+3 to balance it out?
(edited 8 years ago)
Original post by z33
click advanced and it'll come up with formatting options
clicking X2 = subscript and X2 = superscript


Ah I'm on the mobile browser version so the option isn't readily there. Thanks though!
Original post by apronedsamurai
Ok, so I am getting a little confused by the half equations/oxidation numbers....

HNO3(aq) + H3AsO3 NO(g) + H3AsO4(aq) + H2O(l)

Identify which elements have been oxidised or reduced first
Reply 9
Original post by apronedsamurai
Ok, so I am getting a little confused by the half equations/oxidation numbers....

HNO3(aq) + H3AsO3 NO(g) + H3AsO4(aq) + H2O(l)


well in HNO3, the N has an oxidation state of +5, and then in the products (NO), N has an oxidation state of +2, so it's been reduced

the oxidation of As before is +3, and after it's +5 so it's been oxidised
Original post by Serine Soul
Identify which elements have been oxidised or reduced first


I am working on the oxidation numbers to determine that.....
Original post by z33
well in HNO3, the N has an oxidation state of +5, and then in the products (NO), N has an oxidation state of +2, so it's been reduced

the oxidation of As before is +3, and after it's +5 so it's been oxidised


Nah, I knew that Z33, I was just making sure I had gotten the formatting right, and had then amended my post :smile:
Original post by z33
well in HNO3, the N has an oxidation state of +5, and then in the products (NO), N has an oxidation state of +2, so it's been reduced

the oxidation of As before is +3, and after it's +5 so it's been oxidised


HNO3(aq) + H3AsO3 NO(g) + H3AsO4(aq) + H2O(l)

HNO3(aq) H =1 N = 5 and O = -6 (Because 3x-2) and -6+5+1 =0

H3AsO3 H=3 (3x1) As=5 (Because group 5) and O = -6 (3x2)

But that means 3+-6+5=+2....? :|

Or should it be H =3 O =-6 and As =+3 to balance it out?
Reply 13
Original post by apronedsamurai
Nah, I knew that Z33, I was just making sure I had gotten the formatting right, and had then amended my post :smile:


oooooooooooooooooooooooh oops :blush:
Original post by apronedsamurai
I am working on the oxidation numbers to determine that.....


As a general rule of thumb O = -2, H = +1, with exceptions of course

Can you work that out now?
Original post by z33
oooooooooooooooooooooooh oops :blush:


Can you look over my new post please
Reply 16
Original post by apronedsamurai
HNO3(aq) + H3AsO3 NO(g) + H3AsO4(aq) + H2O(l)

HNO3(aq) H =1 N = 5 and O = -6 (Because 3x-2) and -6+5+1 =0

H3AsO3 H=3 (3x1) As=5 (Because group 5) and O = -6 (3x2)

But that means 3+-6+5=+2....? :|

Or should it be H =3 O =-6 and As =+3 to balance it out?


yeah it should be H = +3 and O = -6 because H is always +1 and O is always -2 so you work with them instead of As
Original post by apronedsamurai


Or should it be H =3 O =-6 and As =+3 to balance it out?

That's correct :yep:
Original post by z33
yeah it should be H = +3 and O = -6 because H is always +1 and O is always -2 so you work with them instead of As


PRSOM :colondollar:
Reply 19
Original post by apronedsamurai
PRSOM :colondollar:


:biggrin: :biggrin: :biggrin:

Quick Reply

Latest