VCE Chemistry Question Thread

[warya]

Why, in terms of potential difference/voltage/electronegativity, does the strongest oxidant react with the strongest reductant? Having difficulty explaining it using those terms

[RazzMeTazz]

I don't really understand this question from my Heinemann textbook:

A student working in the laboratory spilled an iodine solution over the bench, causing a dark brown stain to form. Suggest how the student could remove the iodine stain.

The answer is: "The brown stain contains iodine (I2). A reductant stronger than I– ions would react with iodine. By referring to the electrochemical series, you can see that a solution containing Sn2+ ions might react and cause the stain to be removed."

Does this mean that I- ions do not have the brown stain associated with I2? Also, since the solution contains Sn2+ and no solid Sn, I don't see how the I2 could be reduced to form I-?

Thanks

[jyodesh.com]

Why, in terms of potential difference/voltage/electronegativity, does the strongest oxidant react with the strongest reductant? Having difficulty explaining it using those terms

The stronger an oxidant, the greater chemical potential energy it contains. Thus it has a greater capacity to generate an electronic potential difference when used in an electrochemical cell.
In other words the atoms of a strong reductant has electrons that they're holding on to that theyd rather get rid of. The atoms of a strong oxidant wants to get more electrons. The difference in this electrical potential describes how much these two chemicals want electrons and thus the direction at which electrons will move and the energy at which they move. This energy associated with a certain amount of electrical charge is called its voltage

[jyodesh.com]

Does this mean that I- ions do not have the brown stain associated with I2?

Yeah thats what its suggesting

Also, since the solution contains Sn2+ and no solid Sn, I don't see how the I2 could be reduced to form I-?

Solid tin isnt actually needed for the reduction of I2 to occur. Yes solid tin is a stronger reductant than Sn2+, but Sn2+ is still strong enough to be reduced to Sn4+. I think the reason why they said to use Sn2+ instead of solid tin is because Sn2+ would be present in an aqueous solution allowing reaction to occur because rubbing a stain with solid tin would just be ridic

[lzxnl]

The stronger an oxidant, the greater chemical potential energy it contains. Thus it has a greater capacity to generate an electronic potential difference when used in an electrochemical cell.
In other words the atoms of a strong oxidant have electrons that they're holding on to that theyd rather get rid of. The atoms of a strong reductant wants to get more electrons. The difference in this electrical potential describes how much these two chemicals want electrons and thus the direction at which electrons will move and the energy at which they move. This energy associated with a certain amount of electrical charge is called its voltage

You can make analogies between acid-base and redox chemistry. Think of pKas and pKbs (measure of basicity) as analogs of the electrode potentials. In either case, reactive things react together as that reaction has the biggest equilibrium constant.

[RazzMeTazz]

Yeah thats what its suggesting

Solid tin isnt actually needed for the reduction of I2 to occur. Yes solid tin is a stronger reductant than Sn2+, but Sn2+ is still strong enough to be reduced to Sn4+. I think the reason why they said to use Sn2+ instead of solid tin is because Sn2+ would be present in an aqueous solution allowing reaction to occur because rubbing a stain with solid tin would just be ridic

Oh, okay, so the Sn2+ could be further oxidised to something like Sn4+ ?

[Sundal]

Do we need to be able to explain the specifics of how a bomb calorimeter and solution calorimeter work? Is it sufficient just to be able to know enough to do questions involving calorimeters -  relating to enthalpy changes?

Also to calculate the heat of vaporisation, would a bomb calorimeter be  used, not a solution calorimeter?

Cheers

[IntelxD]

The stronger an oxidant, the greater chemical potential energy it contains. Thus it has a greater capacity to generate an electronic potential difference when used in an electrochemical cell.
In other words the atoms of a strong oxidant have electrons that they're holding on to that theyd rather get rid of. The atoms of a strong reductant wants to get more electrons. The difference in this electrical potential describes how much these two chemicals want electrons and thus the direction at which electrons will move and the energy at which they move. This energy associated with a certain amount of electrical charge is called its voltage

Shouldn't it be the other way around with oxidants and reductants?

[jyodesh.com]

Shouldn't it be the other way around with oxidants and reductants?

Holy shit you are ABSOLUTELY CORRECT MAH BAHD (edit time eheh)

Oh, okay, so the Sn2+ could be further oxidised to something like Sn4+ ?

yeah the half equation for this reaction is in the data book

[Sundal]

Are potential difference/volts/emf all the same thing?
Cheers

[paper-back]

Are potential difference/volts/emf all the same thing?
Cheers

Pretty much

[Sundal]

Are galvanic cell/ volatic cell/ daniell cell all the same thing?

Do they all refer to cells in with spontaneous redox reactions occurring?

Cheers again

[HighTide]

Are galvanic cell/ volatic cell/ daniell cell all the same thing?

Do they all refer to cells in with spontaneous redox reactions occurring?

Cheers again

Galvanic and voltaic are the same. Daniell cell is a type of galvanic cell (basically the same) but with copper and zinc. All three are electrochemical cells. Yes, all three are spontaneous.

[odeaa]

Do we have to memorise the reactions in all the different types of cells? Or just the Laclanche? Study design is a bit vague here

Cheers

[jyodesh.com]

Do we have to memorise the reactions in all the different types of cells? Or just the Laclanche? Study design is a bit vague here

Cheers

You do not have to remember any reactions in any cells for the exam including Leclanche. If the half equation isnt in the data book it will be given to you.
If youre teacher says you need to know it for a SAC then you should probably learn it then