Oxidation state?!?!? (1 Viewer)

[Prawnchip]

One test used for random breath testing in NSW involved crystals of potassium dichromate reacting with ethanol. In this reaction the orange dichromate ion, Cr2O2− 7, changes to the green chromium ion, Cr 3+. Which statement is true for this reaction?


(A) Chromium has lost electrons and reached a lower oxidation state.
(B) Chromium has lost electrons and reached a higher oxidation state.
(C) Chromium has gained electrons and reached a lower oxidation state.
(D) Chromium has gained electrons and reached a higher oxidation state.



plz help

 

[HeroicPandas]

One test used for random breath testing in NSW involved crystals of potassium dichromate reacting with ethanol. In this reaction the orange dichromate ion, Cr2O2− 7, changes to the green chromium ion, Cr 3+. Which statement is true for this reaction?


(A) Chromium has lost electrons and reached a lower oxidation state.
(B) Chromium has lost electrons and reached a higher oxidation state.
(C) Chromium has gained electrons and reached a lower oxidation state.
(D) Chromium has gained electrons and reached a higher oxidation state.



plz help

Alright

Cr₂O₂^-7 -------------> Cr³⁺

We need to find the oxidation state of this bad-ass: Cr₂O₂^-7

Oxygen has an oxidation state of -2

This is polyatomic ion, hence oxidation states will ADD up to its CHARGE, in this case, its -7

There are 2 oxygens, hence total sum of the oxygen is 2 x -2 = -4

Hence chromium is -3

(sorry if this is a crappy explanation)

-3 --> 3+

Increase in oxidation state means oxidation has occured, which is lost of electrons

hence answer is B

 

[Prawnchip]

Alright

Cr₂O₂^-7 -------------> Cr³⁺

We need to find the oxidation state of this bad-ass: Cr₂O₂^-7

Oxygen has an oxidation state of -2

This is polyatomic ion, hence oxidation states will ADD up to its CHARGE, in this case, its -7

There are 2 oxygens, hence total sum of the oxygen is 2 x -2 = -4

Hence chromium is -3

(sorry if this is a crappy explanation)

-3 --> 3+

Increase in oxidation state means oxidation has occured, which is lost of electrons

hence answer is B

It's supposed to be C ://///

 

[maalaka]

the orange dichromate ion, Cr2O2− 7

You have either read it wrong or written it wrong, either way dichromate is Cr2O7 2- (seven oxygens with a negative two charge not two oxygens with a negative seven charge)

this means that the Chromate has a oxidation state of 6+ hence the answer has to be C

 

[ocatal]

You have either read it wrong or written it wrong, either way dichromate is Cr2O7 2- (seven oxygens with a negative two charge not two oxygens with a negative seven charge)

this means that the Chromate has a oxidation state of 6+ hence the answer has to be C

+1

 

[bedpotato]

You have either read it wrong or written it wrong, either way dichromate is Cr2O7 2- (seven oxygens with a negative two charge not two oxygens with a negative seven charge)

this means that the Chromate has a oxidation state of 6+ hence the answer has to be C

Yeah, this is right.

THe oxidation state of chromium goes from 6+ --> 3+
So, it has gained 3 electrons and the oxidation state has decreased.

 

[HeroicPandas]

It's supposed to be C ://///

the way u typed it confused me

Thought it was (Cr2O2)(7-) instead of (Cr2O7)(2-)

 

[someth1ng]

There's [ SUP]/[ /SUP] and [ SUB]/[ /SUB].

Use those in future.

 

[Prawnchip]

the way u typed it confused me

Thought it was (Cr2O2)(7-) instead of (Cr2O7)(2-)

oh woops sorry!
thanks so much for the help HeroicPandas