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confuted
10-27-2003, 09:31 PM
I'm supposed to write a balanced equation for this:

"A solid piece of bismuth is strongly heated in oxygen"

I got 4Bi + 5O2 ---> 2Bi2O5 but the girl I'm trying to help with chem doesn't agree. Can someone either tell me I'm right or tell me I'm an idiot? thanks

axon
10-27-2003, 09:50 PM
I thought that your equation was wrong, and to verify it had to take out my big ol' chem book, and indeed, the proper equation is

Bi + O2 = Bi2O3

remember, it really doesn't have to say "in oxygen",

axon

EDIT:: just to double check if I was right I typed thedescription of the reaction in google, here are a couple of the results from the first page:

result 1 (http://216.239.57.104/search?q=cache:XC4TUfwP9j0J:library.thinkquest.org/C006669/data/Chem/reactions/set1a.html+A+solid+piece+of+bismuth+is+strongly+he ated+in+oxygen&hl=en&ie=UTF-8) problem 7

here look at answer (g) (http://www.spusd.k12.ca.us/chemmybear/answers.html#1990)

EDIT 2:: hey confuted, whatever came from the CD experiment? did you get any good data? did you even do it?

confuted
10-27-2003, 09:59 PM
why doesn't Bi have a +5 oxidation number?

Leeman_s
10-27-2003, 10:12 PM
The unbalanced equation is Bi + O2 --> Bi2O3

The balanced equation is 4Bi + 3O2 --> 2Bi2O3

The most stable oxidation state for bismuth is +3. If it was Bi(V) then you would use the +5 oxidation state. If it was indeed Bi(V) then your equation would be right, but since it's not specified use +3 which is more stable.

Clyde
10-28-2003, 04:30 PM
why doesn't Bi have a +5 oxidation number?


Heavier elements have larger more diffuse orbitals hence form weaker bonds.

In order to form 5 bonds (formal oxidation state 5+), electrons in the s orbital need to be promoted to sp hybridised orbitals this takes energy, in lighter elements this is offset by the strongly stabilising effect of forming 2 extra bonds. However for heavier elements like Bismuth the energy required to promote the electrons is greater the the energy released via formation of the extra bonds, so it only forms 3 bonds (formal oxidation state 3+). This is known as the "inert pair effect".

ZakkWylde969
10-28-2003, 04:41 PM
Also your equations coeffecients don't add up. There is supposed to be an equal amount on both sides.

confuted
10-28-2003, 06:06 PM
Originally posted by ZakkWylde969
Also your equations coeffecients don't add up. There is supposed to be an equal amount on both sides.

They added up.

4Bi + 5O2 ---> 2Bi2O5

4 Bi ---> 2 Bi2 = 4Bi
5 O2 = 10 O ---> 2 * O5 = 10 O

The reason I got it wrong was just that I was using 5 for the oxidation number of Bi. I didn't realize my periodic table had a list of the oxidation numbers, with the most common one in bold (heh, it was kinda late and I was tired)

golfinguy4
10-29-2003, 02:56 PM
Originally posted by Clyde
Heavier elements have larger more diffuse orbitals hence form weaker bonds.

In order to form 5 bonds (formal oxidation state 5+), electrons in the s orbital need to be promoted to sp hybridised orbitals this takes energy, in lighter elements this is offset by the strongly stabilising effect of forming 2 extra bonds. However for heavier elements like Bismuth the energy required to promote the electrons is greater the the energy released via formation of the extra bonds, so it only forms 3 bonds (formal oxidation state 3+). This is known as the "inert pair effect".


Err... A definate Chem major.

axon
10-29-2003, 03:15 PM
Originally posted by golfinguy4
Err... A definate Chem major.

I don't think so...this is all from general college chem 1, as I can remember.

Clyde
10-29-2003, 03:35 PM
I don't think so...this is all from general college chem 1, as I can remember.


I don't think I covered the inert pair effect pre-uni but its possible, its not complex of itself though I suspect a grasp of terms like "orbitals" and why they get "diffuse" for heavier elements and why them being "diffuse" weakens bonding in this instance (why indeed bond formation is stabilising) will be fairly poor prior to university chemistry.

Silvercord
10-29-2003, 03:37 PM
clyde is a chemistry major, he's helped me before, I think...

golfinguy4
10-29-2003, 10:06 PM
Yea, I know he is. I cheated.

Leeman_s
10-31-2003, 01:06 AM
I'm taking AP Chem at school....redox sucks balls

confuted
10-31-2003, 07:55 AM
Originally posted by Leeman_s
I'm taking AP Chem at school....redox sucks balls
Functional groups are a lot worse (unless you like memorization)