CE Chemistry - Electrolysis

vctwl

Using carbon electrodes, what will happen if molten copper(II) dichromate is under electrolysis?

sorry ... 加番
呢個先係我想問gei問題

[ Last edited by vctwl on 13-2-2005 at 07:39 PM ]

bobby_zamora

Originally posted by vctwl at 2005-2-10 08:38 PM:
Using carbon electrodes, what will happen if copper(II) dichromate is under electrolysis?

...............
Cu2Cr2O7????

does it exist...?
if really...then i will say nothing will happen
both Cu+ and Cr2O72- will carry out reduction and not current will be formed

Newcastle Fans

Originally posted by bobby_zamora at 2005-2-11 22:48:

...............
Cu2Cr2O7????

does it exist...?
if really...then i will say nothing will happen
both Cu+ and Cr2O72- will carry out reduction and not current will be formed

...... Cu(II) = Cu2+
copper(II) dichromate should be CuCr2O7

[ Last edited by Newcastle Fans on 11-2-2005 at 11:09 PM ]

Newcastle Fans

There will be deposition of reddish brown solid of Cu at the cathode
and... there'll be some green solution around the anode?
just a guess

[ Last edited by Newcastle Fans on 11-2-2005 at 11:10 PM ]

bobby_zamora

Originally posted by Newcastle Fans at 2005-2-11 11:06 PM:
CuCr2O7
...... Cu(II) = Cu2+
copper(II) dichromate should be CuCr2O7

[ Last edited by Newcastle Fans on 11-2-2005 at 11:09 PM ]

shxx
miss out the II

bobby_zamora

Originally posted by Newcastle Fans at 2005-2-11 11:07 PM:
There will be deposition of reddish brown solid of Cu at the cathode
and... there'll be some green solution around the anode?
just a guess

[ Last edited by Newcastle Fans on 11-2-2005 at 11: ...

no...i don't think so...
Cu2+ to copper..is reduction...
green solution..is cr3+..
cr2o7 to cr3+ still is reduction..
2 reduction..happen in a chemical cell??

vctwl

主要問題係:
1. dichromate 無 acidified
2. copper(II) 同 dichromate 都係 oxidizing agent
3. 無 reaction?
4. 照通電?

martinsy39

ther are 4 kinds of ions in the solution: Cu2+,Cr2O72-,H+,andOH-
according to electrochemical series, Cu2+ and OH- will be discharged.
half equation: Cu2+ +2e- ->2Cu
                    4OH- ->O2 + 2H2O + 4e-
reddish brown solid will deposit on the cathode, and colourless gas bubbles will be produced on the anode

[ Last edited by martinsy39 on 13-2-2005 at 01:00 PM ]

vctwl

Originally posted by martinsy39 at 2005/2/13 12:46 PM:
ther are 4 kinds of ions in the solution: Cu2+,Cr2O72-,H+,andOH-
according to electrochemical series, Cu2+ and OH- will be discharged.
half equation: Cu2+ +2e- ->2Cu
                    4OH- ...

sorry
我想問 molten ...

[ Last edited by vctwl on 13-2-2005 at 07:42 PM ]

2076

Originally posted by vctwl at 2005-2-13 01:16 PM:


molten bor

上面都無講

2076

Originally posted by martinsy39 at 2005-2-13 12:46 PM:
ther are 4 kinds of ions in the solution: Cu2+,Cr2O72-,H+,andOH-
according to electrochemical series, Cu2+ and OH- will be discharged.

but Cr2O7^2- is a stronger oxidizing agent than Cu^2+

vctwl

Originally posted by 2076 at 2005/2/13 05:19 PM:


上面都無講

sorry

martinsy39

Originally posted by 2076 at 2005-2-13 05:22 PM:


but Cr2O7^2- is a stronger oxidizing agent than Cu^2+

i think anion will not act as an oxidizing agent in electrolysis, just like NO3-
Also, what is the difference between molten copper2 dichromate and not molten one?

2076

Originally posted by martinsy39 at 2005-2-13 09:08 PM:

Also, what is the difference between molten copper2 dichromate and not molten one?

Molten係pure
唔molten係個chemical溶左落水度, 有H+同OH-(orO^2-)
唔知係咪咁

martinsy39

then if molten
cathode: Cu2+ +2e- ->2Cu
anode: Cr2O72- + 14H+ + 6e- ->2Cr3+ +7H2O

2076

Originally posted by martinsy39 at 2005-2-13 10:51 PM:
then if molten
cathode: Cu2+ +2e- ->2Cu
anode: Cr2O72- + 14H+ + 6e- ->2Cr3+ +7H2O

最主要問題係, anode係lose electrons既地方, 點可以進行reduction?

所以搞咁耐, 我認為係無反應的

martinsy39

yes, you are right