VCE Chemistry Question Thread

[idontknow2298]

sorry I mean't more than 1 branch
Here's an example: CH3BrCHCH2CH2CH2OH
Would OH be numbered first or Br?
Thank you

[lzxnl]

There is a hierarchy of chemical functional groups:
Acid > amide > ester > nitrile > aldehyde/ketone > alcohol > amine > alkene > alkyne > alkane = halogen

You always put halogens at the front, but you don't always put alcohols at the front. Anything with a higher priority than an alkane will have a special ending at the end. So your molecule has a hydroxyl -> must put -ol at the end. The bromine goes at the front.
The rule is, the numbering should first and foremost reduce the number of what you have at the end. In this case, your molecule would be called 4-bromopentan-1-ol.

[idontknow2298]

sorry, what does "the numbering should first and foremost reduce the number of what you have at the end" mean?

[lzxnl]

sorry, what does "the numbering should first and foremost reduce the number of what you have at the end" mean?

So, there are two ways I could have named this molecule. I could have labelled the hydroxy group as 1 or 5 depending which side I counted from. As the hydroxyl label is at the end, I need to number the molecule such that the hydroxyl label is smaller, so I label it 1.

[idontknow2298]

Oh, I get it now, thank you so much! 

[idontknow2298]

Hi everyone, I just want to ask how do you use the electrochemical series to determine whether a redox reaction will happen or not?

[keltingmeith]

Hi everyone, I just want to ask how do you use the electrochemical series to determine whether a redox reaction will happen or not?

I reckon the easiest way is to calculate the electrode potential of a cell constructed of just those two things. If the potential is positive, the reaction will happen. If the potential is negative, it won't. (not quite as clear cut as that, but it works for VCE)

[HighTide]

Hi everyone, I just want to ask how do you use the electrochemical series to determine whether a redox reaction will happen or not?

If you have a diagonal going from top left to bottom right, a redox reaction occurs. Top right to bottom left= no redox reaction occurs.

[idontknow2298]

When looking for the diagonal, where would I start? For example zinc and aluminium chloride, would I start with Zn2+ or Zn, and then move diagonally to Al or Cl?

[ally12579]

When looking for the diagonal, where would I start? For example zinc and aluminum chloride, would I start with Zn2+ or Zn, and then move diagonally to Al or Cl?

You use the reactants that you have to work out if they would reaction. As you have Zn and Al3+, you would draw a diagonal line between the two. If the line has a negative gradient (using the electrochemical series from the textbook or VCAA data booklet, not necessarily for other electrochemical series) the reaction will happen, if it is a positive gradient, then the reaction will not occur.
Hope this helps 

[idontknow2298]

But for when lead nitrate solution is poured into a beaker containing zinc granules, isn't Zn(s) diagonal to Pb 2+ in a negative gradient on the electrochemical series? How come there is no reaction?

[lzxnl]

If there's no reaction, your first thought should be, maybe the reaction is just slow.
The electrochemical series tells you nothing about reaction rates.

[idontknow2298]

Hi everyone, I would like some help with this question please:
What mass of aluminium fluoride, AlF3 would be required to make 100mL of a solution that has fluoride ion concentration of 0.300M?

[keltingmeith]

Hi everyone, I would like some help with this question please:
What mass of aluminium fluoride, AlF3 would be required to make 100mL of a solution that has fluoride ion concentration of 0.300M?

Have they given you any other information? (in particular, I'm looking for a K value, might be labelled as Ksp)

[lzxnl]

Have they given you any other information? (in particular, I'm looking for a K value, might be labelled as Ksp)

Wiki says AlF3 isn't particularly soluble
You could use that