Chemistry: Post your doubts here!

[My Name]

View attachment 58131
25 a and b
I guess I know the answer, but I am not sure if I am 100% correct.
a) From all three Cr2+ has least positive E(std) value. Hence it needs the strongest reducing agent (more -ve E(std) value agent) to reduce it.
b) From all three Ag has most posivtive E(std) value. Hence it needs the strongest oxidising agent (more +ve E(std) value agent) to oxidise it.
M I corrct? If not then do correct me. Thanks.
Metanoia
DarkEclipse
Dark Destination
awesomaholic101
FranticAmaze
My Name

Didn't get the tag.
I think you're answers are right.
Doesn't the book have answers at the back?
awesomaholic101 FranticAmaze Midnight dream Lola_sweet What do you say?

 

[awesomaholic101]

Didn't get the tag.
I think you're answers are right.
Doesn't the book have answers at the back?
awesomaholic101 FranticAmaze Midnight dream Lola_sweet What do you say?

Those answers better be right .. Coz I would say that too and I don't want to be wrong

 

[Metanoia]

View attachment 58131
25 a and b
I guess I know the answer, but I am not sure if I am 100% correct.
a) From all three Cr2+ has least positive E(std) value. Hence it needs the strongest reducing agent (more -ve E(std) value agent) to reduce it.
b) From all three Ag has most posivtive E(std) value. Hence it needs the strongest oxidising agent (more +ve E(std) value agent) to oxidise it.
M I corrct? If not then do correct me. Thanks.
Metanoia
DarkEclipse
Dark Destination
awesomaholic101
FranticAmaze
My Name

Yes. That is correct. You can also use O level chemistry to check your answer- in decreasing reactivity of metals, Chromium, Iron and Silver.

So the most stable ion is Cr2+ and the most stable metal is Ag.

They will require the strongest reducing agent and oxidizing agent respectively to under changes.

 

[nehaoscar]

Anyone with the new 2016 coursebook, please can you tell me if High-performance liquid chromatography (HPLC) is given in the text book??
It's not in the syllabus so do I need it??

 

[The Sarcastic Retard]

Yes. That is correct. You can also use O level chemistry to check your answer- in decreasing reactivity of metals, Chromium, Iron and Silver.

So the most stable ion is Cr2+ and the most stable metal is Ag.

They will require the strongest reducing agent and oxidizing agent respectively to under changes.

THanks....

 

[Saad the Paki]

Q3. Help please. The answer is B.

 

[Metanoia]

Q3. Help please. The answer is B. View attachment 58386

Eqn 1 is reduction.
Eqn 2 is oxidation.

You need to make sure the number of electrons are the same before combining or comparing.

Therefore you need to multiply eqn 2 throughout by 2.

 

[HumptyR]

Let the Q1 be solved.

 

[nehaoscar]

Find AS organic chemistry reagents chart here:
https://www.xtremepapers.com/commun...c-chemistry-reagents-chart.42668/#post-949384

 

[HumptyR]

 

[holoholo]

When concentrated nitric acid, HNO3, is added to copper turnings, a brown gas is evolved. Use data from the Data Booklet to construct an ionic equation for this reaction.
which equation of copper should i use and why ?

 

[HumptyR]

When concentrated nitric acid, HNO3, is added to copper turnings, a brown gas is evolved. Use data from the Data Booklet to construct an ionic equation for this reaction.
which equation of copper should i use and why ?

Well you should use this eq. :Cu + 4H+ + 2NO3– → Cu2+ + 2NO2 + 2H2O. Because it is ionic :3

 

[holoholo]

why can't we use Cu+ instead of Cu2+ ?

 

[HumptyR]

why can't we use Cu+ instead of Cu2+ ?

Well, IDK :3 But i guess we can't use Cu+ simply because NO2 and H2O need e- :3

 

[nehaoscar]

why can't we use Cu+ instead of Cu2+ ?

What does the ms say? Usually they allow both reactions ...

 

[nehaoscar]

Well, IDK :3 But i guess we can't use Cu+ simply because NO2 and H2O need e- :3

Even Cu+ has e-

 

[HumptyR]

Even Cu+ has e-
View attachment 58619

But according to the eq H2O and NO2 require two e-

 

[nehaoscar]

But according to the eq H2O and NO2 require two e-

Hmm yeah ... But can't you multiply the Cu+ eqn by 2 so to get 2e-?

 

[HumptyR]

Hmm yeah ... But can't you multiply the Cu+ eqn by 2 so to get 2e-?

Copper is oxidized by concentrated nitric acid, HNO3, to produce Cu2+ ions; the nitric acid is reduced to nitrogen dioxide, a poisonous brown gas with an irritating odor. The question says brown gas is formed so here i win.

 

[nehaoscar]

Copper is oxidized by concentrated nitric acid, HNO3, to produce Cu2+ ions; the nitric acid is reduced to nitrogen dioxide, a poisonous brown gas with an irritating odor. The question says brown gas is formed so here i win.

What I'm saying is why can't it be this equation too:
NO3- + 2H+ + Cu = NO2 + H2O + Cu+
Here NO2 is also formed...

So can't it be either or equations?
---> 2NO3- + 4H+ + Cu = 2NO2 + 2H2O + Cu2+
---> NO3- + 2H+ + Cu = NO2 + H2O + Cu+