[istrydummy]

So i have done some experiments and now i have to describe my observations and give an explanation of the reaction which occurs. I also have to give chemical equations where i can.

1)
A solution of sodium metavanadate in 6M sulphuric acid was made to give a yellow colour. And then zinc granules were added.

Observations: Fizzing bubbles coming from the  Zinc granules. Solution turns lime green > to a sky blue colour> slightly exothermic (test tube is warm) > solution turns turquoise > solution turns back to lime green.

Explanation: I dont know why sulphuric acid is used in the first place. Is it used to dissociate the sodium metavanadate? I also dont know why Zn is fizzing...Isn't sodium  more reactive than Zn? Shouldnt nothing happen?

Chemical equations:    NaVO₃ + Zn  Zn(VO₃)₂ Is this the right quation or is there is also a reaction between sodium metavanadate and suphuric aicd?



2)
a)To Iron (II) Sulphate  a few drops of Phenanthroling was added.[/color]

Observations: Pale orange colour ( Fanta drink)

Explanation: does it have something to do with the complex formed?

Chemical equations: I really need help in this part. I think a (tris)-1,10-Phenanthroline Iron (II) compound is formed, but i aint sure.



b) To Iron (II) Sulphate a few drops of  Potassium thiocyanate was added.

Observations: Pale orange colour ( Fanta drink)


Explanation: does it have something to do with the complex formed?

Chemical equations: i need help on this part.




c)To Iron (III) sulphate  a few drops of Phenanthroling was added.

Observations: a cloudy red colour was observed

Explanation: does it have something to do with the complex formed?

Chemical equations: i need help on this part.


3)
A solution of aq potassium permanganate is made to give a deep purple solution. Same volume of sodium hydroxide  is added and eventually the solution was poured onto a filter paper.

Observations: On the filter paper, colour change was from purple  > green > brown

Explanation: Purple colour due to permanganate being ⁷⁺ charge. I dont know why the green colour is formed. I think the brown colour is formed due to oxidizing cellulose, but im not sure.

Chemical equations: MnO⁻ + OH ^-     KOH + NaMnO₄ Is this the right equation?  If yes, which is it the NaMnO₄ that gives the colour changes?


4)
A solution of Nickel (II) Sulphate was made and to it a few drops of dimethylglyoxime in ethanol solution was added.

Observations: A milky clear colour > pale pink colour> and when dimethylglyoxime was added in excess a very deep pink/red precipitate was formed.

Explanation: I dont know what the role of ethanol is in this reaction and how adding dimethylglyoximeeffects the reaction.

Chemical equations: is some sort of Nickel-dimethylglyoxime complex formed?

?      Ni(II)(DMG)₂



As you can see there are three parts to my problems , given in colours. The parts i have no clue about i am very struggling with and need help with.I have written in each section what areas i need help with. If you help me fill the spaces i need, it would be greatly appreciated.
 


Thank you for your consideration.

PS: If you think you can help, can you please put the number of question before your answer, so it would be easy to understand which part of the problems you are acknowledging.
 

[istrydummy]

Er....anyone? . I have done my best , but cant do anymore. Need help ^^^

[istrydummy]

Maybe its my bad way of asking the questions. If it is, then sorry and i will make it a bit simpler to understand.




1)
A solution of sodium metavanadate in 6M sulphuric acid was made to give a yellow colour. And then zinc granules were added.

Questions:
a) What is the role of the sulphuric acid? . Is it used to dissociate the sodium metavanadate? I also dont know why Zn is fizzing...Isn't sodium more reactive than Zn? Shouldnt nothing happen?

b) NaVO₃ + Zn_(s)   Zn(VO₃)₂ Is this the right quation or is there is also a reaction between sodium metavanadate and suphuric aicd?


2)
To Iron (II) Sulphate  a few drops of Phenanthroline was added.

Questions:
a) I think a (tris)-1,10-Phenanthroline Iron (II) compound is formed, but im not sure how to right the full equation.

FeSO₄  + ?      (tris)-1,10-Phenanthroline Iron (II)

b) the solution turns a fanta (drink) orange colour. Is it the complex giving it the colour characteristic?


3)
 To Iron (II) Sulphate a few drops of  Potassium thiocyanate was added.

Questions:

SCN⁻ + Fe³⁺   [Fe(NCS)(H₂O)₅]^2+.   Is this the right equation? i feel like i am confusing Fe ³⁺ with Fe ²⁺

4)
A solution of aq potassium permanganate is made to give a deep purple solution. Same volume of sodium hydroxide  is added and eventually the solution was poured onto a filter paper.


Questions:

a)There are 3 colour changes. From purple to green to brown. I know why i have purple , its due to the permanganate +7. I dont know why i get the green colour and im not sure about the brown colour ( cellulose)?

b) MnO⁻ + OH ^-     KOH + NaMnO₄ Is this the right equation?

[Borek]

Maybe its my bad way of asking the questions. If it is, then sorry and i will make it a bit simpler to understand.

I am afraid problem is - you are showing complete ignorance yet you seem to be working with some advanced concepts. In effect everybody is afraid of answering, as explaining everything from the very beginning is a task for textbook or lecture, not for us. We can help you understanding once you already know something.

Let's see parts of the first part.

[1)
A solution of sodium metavanadate in 6M sulphuric acid was made to give a yellow colour. And then zinc granules were added.

Questions:
a) What is the role of the sulphuric acid? . Is it used to dissociate the sodium metavanadate?

Acids are not used to "dissociate" anything. If somethings dissociates, it dissociates just in the presence of water.

I also dont know why Zn is fizzing...

Reactive metal in the presence of strong acid.

Isn't sodium more reactive than Zn?

Zinc is metallic, sodium is in cationic form. You are comparing apples and oranges.

Shouldnt nothing happen?

Even if there were no metavanadate, zinc should react with sulfuric acid.

b) NaVO₃ + Zn_(s)   Zn(VO₃)₂ Is this the right quation or is there is also a reaction between sodium metavanadate and suphuric aicd?

No, it is not the correct equation, it is not even close to the real processes happening in the solution.

[istrydummy]

Maybe its my bad way of asking the questions. If it is, then sorry and i will make it a bit simpler to understand.

I am afraid problem is - you are showing complete ignorance yet you seem to be working with some advanced concepts. In effect everybody is afraid of answering, as explaining everything from the very beginning is a task for textbook or lecture, not for us. We can help you understanding once you already know something.

Let's see parts of the first part.

[1)
A solution of sodium metavanadate in 6M sulphuric acid was made to give a yellow colour. And then zinc granules were added.

Questions:
a) What is the role of the sulphuric acid? . Is it used to dissociate the sodium metavanadate?

Acids are not used to "dissociate" anything. If somethings dissociates, it dissociates just in the presence of water.

I also dont know why Zn is fizzing...

Reactive metal in the presence of strong acid.

Isn't sodium more reactive than Zn?

Zinc is metallic, sodium is in cationic form. You are comparing apples and oranges.

Shouldnt nothing happen?

Even if there were no metavanadate, zinc should react with sulfuric acid.

b) NaVO₃ + Zn_(s)   Zn(VO₃)₂ Is this the right quation or is there is also a reaction between sodium metavanadate and suphuric aicd?

No, it is not the correct equation, it is not even close to the real processes happening in the solution.

Ouch. This comment was a kick in my backside, and it humbled me. So, thanks for that. ( Sincerely ). It needed to be said.

I will try to explain my thinking and please tell me where i am going wrong.:

Vanadium has oxidation states in its compounds of +5 , +4 , +3 , +2.
So the source of the + 5 state is the Sodium metavanadate ( NaVO₃) which is a yellow solution. The zinc in sulphuric acid acts as a reducing agent.

The main ion present at the beginning of the experiment is VO₂⁺, more accurately written as [VO₂(H₂O)₄ ]⁴⁺ .

Observations

The solution turns from yellow(+5)  to green to blue(+4)  to turquoise (+3)  to purple (+2) and then back to turquoise then to blue etc, ( due to re-oxidation).
The values are the oxidation states.

The ions in presence of water molecules:

The Vanadium (V) ion = [VO₂(H₂O)₄ ]⁴⁺  Yellow
The vanadium (VI)ion = [VO₂(H₂O)₅ ]²⁺ Blue
The vanadium (III)ion= [V(H₂O)₆ ]³⁺  Turquoise/Green
The vanadium (II)ion = [V(H₂O)₆ ]²⁺ Purple

Are these right? I have a feeling the last two are off, somehow.

Explaining in terms of half-cell equations:

Basically , i combined the red-ox potentials for the vanadium half reaction and the zinc to get for the initial reduction:

2VO₂+ _(aq) + 4H⁺ _(aq) + Zn_(s)  2VO²+ _(aq) + 2H₂O + Zn²⁺ _(aq)

And so on for the rest. If i got this one right, then im sure i have the others right aswell. Just need to check this one ^^.


Thanks for your consideration.

[Borek]

The main ion present at the beginning of the experiment is VO₂⁺, more accurately written as [VO₂(H₂O)₄ ]⁴⁺

This can't be right, water molecules are neutral, so if you start with VO₂⁺ you end with [VO₂(H₂O)₄ ]⁺

[istrydummy]

The main ion present at the beginning of the experiment is VO₂⁺, more accurately written as [VO₂(H₂O)₄ ]⁴⁺

This can't be right, water molecules are neutral, so if you start with VO₂⁺ you end with [VO₂(H₂O)₄ ]⁺

O yes. My bad. Thanks. But does the rest look ok?

[Borek]

No idea, but I believe inorganic chemistry textbooks will contain more information about vanadates that I have in my head.

[istrydummy]

I have managed to do most of the questions i asked on this thread, but i am confused on two of them:

1) Iron (II) Sulfate + a few drops of potassium Thiocyanate solution.

When i did this experiment, i notices a pale orange ( fanta drink)  colour appearing.


Question :

SCN⁻ + Fe²⁺    [Fe(NCS)(H2O)5]^+.
Is this the right equation which would explain this reactions?


2) Iron (III) Sulfate + a few drops of phenanthroline.

When i did this experiment i noticed a cloudy red colour appearing.

Fe³⁺ + 3 Phen  [Fe(Phen)₃]³⁺

Question:
Is this the right equation which would explain this reactions?

Thanks.

PS: If you have any source of info on any of these reactions, could you post the link?. I have researched everywhere but finding info on these reactions seems to be limited.

[gggggggggg]

It looks like. Not 100% sure though..