VCE Chemistry Question Thread

[conic curve]

Correct me if I'm wrong, but isn't a cathode the positive electrode and the anode the negative electrode?

Cathode is negative and anode is positive 

[vox nihili]

Correct me if I'm wrong, but isn't a cathode the positive electrode and the anode the negative electrode?

Just to add: remember it's the reverse in electrolysis

[sweetiepi]

My bad! I totally forgot about electrolysis ^_^ (if anybody needs me, I'll be hiding in the Forum Games )

[HasibA]

predicting products at each electrodes for electrolysis; what's the quickest way to predict them? not possible to predict without a electrochem series (at leaast in VCE) , correct?

[HopefulLawStudent]

Is "electrophoresis" in the study design???

[vox nihili]

Is "electrophoresis" in the study design???

Find out for yourself.

[HopefulLawStudent]

That was the first place I checked.

There's a brief mention of it in the study design as an "example of learning activities" or something along those lines for Outcome 2 for Unit 1/2 but no actual mention of it in the key knowledge section for Units 3/4.

BUT

My teacher said that we need to know it but my tutor said we didn't so I'm a bit confused and so I wanted a third opinion.

[jyce]

That was the first place I checked.

There's a brief mention of it in the study design as an "example of learning activities" or something along those lines for Outcome 2 for Unit 1/2 but no actual mention of it in the key knowledge section for Units 3/4.

BUT

My teacher said that we need to know it but my tutor said we didn't so I'm a bit confused and so I wanted a third opinion.

You most definitely do NOT need to about electrophoresis. You used to have to prior to 2013.

[Sine]

pretty much there is actually no knowledge of biotech stuff needed even though many schools still teach it. Althoug ith may be useful to have a rough understanding in the event that they actually explain/teach you techniques such as gel electrophoresis, PCR, DNA profiling etc and make you answer some questions using that and your knowledge of biochemistry.

[Adequace]

When ionic compounds dissociate in water do we have to put the h2o on top of the -> sign? Also, when an acid donates a proton to form a hydronium ion, is this a reaction or is it still considered dissociation?

Getting conflicting answers between my teacher and the textbook.

[zsteve]

When ionic compounds dissociate in water do we have to put the h2o on top of the -> sign? Also, when an acid donates a proton to form a hydronium ion, is this a reaction or is it still considered dissociation?

Getting conflicting answers between my teacher and the textbook.

Nope, don't need the \(\ce{H2O}\), showing (aq) states is fine. As long as it's clear we're getting dissolution.
There's not a clear distinction between the terms 'dissociation' and 'reaction', and in my opinion it's probably unhelpful to think that 'dissociation' and 'reaction' are distinctly different things. Rather, 'dissociation' is when we've got a compound breaking up without chemical rearrangement, technically also a reaction.

For the record, an acid donating a proton is most accurately described as a deprotonation reaction

[Adequace]

Thanks zsteve.

[Sine]

In extended response questions are we allowed to reference the data book? For example say from the electrochemical series  X is a stronger reductant than Y therefore it is oxidised.

[Maz]

In extended response questions are we allowed to reference the data book? For example say from the electrochemical series  X is a stronger reductant than Y therefore it is oxidised.

yeah you could, but I would also add in the E⁰ values as well.

[Sine]

yeah you could, but I would also add in the E⁰ values as well.

thanks

For example
Say in this electrolytic cell there is no membrane seperating the reduction and oxidation
At the Anode we have : \(\ce{2H2O(l)->O2(g) + 4H+(aq) +4e-}\)
At the Cathode we have : \(\ce{2H2O(l) + 2e- -> H2(g) + 2OH-(aq)}\)
Overall is : \(\ce{2H2O(l) -> O2(g) + 2H2(g)}\)
How do we test that the reaction has occured. Can we use universal indicator since H+ is produced at the anode changing pH and like wise with OH-  at the cathode but i'm thinking OH- and H+ react to produce H2O thus no change in pH.
Will they react fast enough for us to be unable to do the test?
Would the only way to check is to observe O2(g) and H2(g) bubbles formed?