Question

Hi guys, one question with a couple of parts!
What is the oxidation state for the atoms in the reaction:
2Al + 8H2O → 2H+1 + 3H2 + 2Al(OH)4-1
a) Elemental aluminum (Al)
b) One hydrogen atom in H2O
c) One oxygen atom in H20
d) Elemental hydrogen (H)
e) One aluminum atom in Al(OH)4-1
f) One oxygen atom in Al(OH)4-1
g) One hydrogen atom in Al(OH)4-1

Answer 1

oxidation state on homonuclear molecules or elemental species = 0

Answer 2

Oxygen = -2 always

Answer 3

you can figure out the rest by balancing the charges

Answer 4

Alright, so for a i got 0, b -3, c -2, d 1, e 2, f -2 and g 0. Are these right?

Answer 5

Let me see if I get this right: You suggest that hydrogen in water have the oxidation number -3?

Answer 6

I believe so

Answer 7

Okay.
We need an additional rule:
"The sum of oxidations numbers most equal to total charge of the molecule."
So when we look at water it have no charge... sense oxygen always get -2 each hydrogen most be what?

Answer 8

-5? And in that equation, which element was reduced and which
was oxidized?

Answer 9

And can verify my answers please?

Answer 10

Best you get some training, so I'm gonna start with water and we take them each by each.
H2O we take notice:
Total charge = 0
oxygen always -2
Hydrogen always +1
This also make sense we should say:
0=-2+2*x <-> x=+1

Answer 11

aluminum is right. again it does not have charge and is an elemental species.

Answer 12

Both hydrogens are positive one as well?

Answer 13

Yes. it is 2 times +1

Answer 14

Alright, so what about for e through g?

Answer 15

hello?

Answer 16

Sorry I was thinking. both e and g are wrong.

Answer 17

The oxidation state of oxygen is -2
the oxidation state of hydrogen is +1:
so we get:
Al(OH)4 -1
-1 = -8+4+x
Here is x the oxidation state of Al..
What is x?

Answer 18

Not quite.

Answer 19

\[-1=-8+4+x\]
\[x=-1+8-4=3\]

Answer 20

So aluminum was reduced, so which was oxidized?

Answer 21

which one are you working on?

Answer 22

g

Answer 23

I need the answer for g and then: In the equation above, which element was reduced and which element was oxidized?

Answer 24

The H on the compound is part of the hydroxide ion, which is OH^-

since O is -2 and theres a -1 charge on ion, H is +1

Answer 25

Awesome. so then which was oxidized and which was reduced?

Answer 26

they're both 0 when not part of a molecule, if one gains e then we say its reduced because it became more negative, the opposite is for oxidized.

Answer 27

I mean for all of the elements in the equations, it seems like aluminum gained electrons

Answer 28

!

Answer 29

we already did everything in the equation