VCE Chemistry Question Thread

[larissaaa_]

In the general gas equation pV = nRT, what unit is the pressure in? Like atm or kPa or Pa? And so do we have to change it to a particular unit before we do calculations?

[julijulib]

In the general gas equation pV = nRT, what unit is the pressure in? Like atm or kPa or Pa? And so do we have to change it to a particular unit before we do calculations?

Must always be in kPa! 

[larissaaa_]

Must always be in kPa! 

Thank you!

[megt]

Any thoughts about the comparable difficulty of NEAP and VCAA chem exams? Thanks

[Swagadaktal]

Any thoughts about the comparable difficulty of NEAP and VCAA chem exams? Thanks

They are much more convoluted

But VCAA abuses its students with some convoluted questions - but not to the extent of neap

[MandhreeE]

The lactic acid should be in an aqueous state, due to it being dissolved in water. It seems that in the previous study design, VCAA would state that acids added to water will be liquids. In the current study design exams depict them as aqueous.

Thank you so much! this really helps so i just keep doing what i have been taught and only include aqueous and gas in the equilibrium expression?
Thanks!

[MandhreeE]

Hey guys!
Would my response to this question "Explain how a catalyst increase the rate of this reaction" by correct?
I know VCAA are quite specific.

"By providing an alternative reaction pathway with a lower activation energy, meaning that more particles have sufficient energy to overcome this new activation energy and thus collide more frequently and successfully and thus increase the rate of reaction"

Thank you!!

[MandhreeE]

another question sorry!

What level of detail do we need to know about DNA? like do we need to know about the 3' to 5' and that they are semi-conservative? Also, do we need to know about DNA replication?

Thank you

[keltingmeith]

Hey guys!
Would my response to this question "Explain how a catalyst increase the rate of this reaction" by correct?
I know VCAA are quite specific.

"By providing an alternative reaction pathway with a lower activation energy, meaning that more particles have sufficient energy to overcome this new activation energy and thus collide more frequently and successfully and thus increase the rate of reaction"

Thank you!!

I think you've rambled a bit much. I reckon that if you had just stated the molecules have sufficient energy to overcome the barrier, you would've been fine - the rambling with collision theory isn't necesarrily wrong, however it's a bad habit to have in chemistry. Too often, I see students rambling, trying their best to say everything they need to to get the marks, and then they say something that IS wrong or irrelevant, and lose marks as a result. How many marks is it worth? Remember, you usually only need to say one thing per mark.


Oops, sorry, missed your second one. You should use the edit function next time!

another question sorry!

What level of detail do we need to know about DNA? like do we need to know about the 3' to 5' and that they are semi-conservative? Also, do we need to know about DNA replication?

Thank you

I don't know what semi-conservative means OR anything about DNA replication, so probably not. The study design only specifically mentions the primary and secondary structures of DNA (primary=sugar-phosphone ester backbone, with four base pairs running along it, made by covalent bonds, secondary=hydrogen bonding between base pairs), as well as the reactions that make them (i.e., condensation reactions. This is the same for all biomolecules you've learned about, btw). Anything else is too much biology for VCAA's liking.

[sweetcheeks]

Hey guys!
Would my response to this question "Explain how a catalyst increase the rate of this reaction" by correct?
I know VCAA are quite specific.

"By providing an alternative reaction pathway with a lower activation energy, meaning that more particles have sufficient energy to overcome this new activation energy and thus collide more frequently and successfully and thus increase the rate of reaction"

Thank you!!

Be careful when talking about collisions. A catalyst won't increase the number of collisions, only the number (or proportion) of successful collisions.

[MandhreeE]

THANK YOU!  melting meithy and sweetcheeks

[ciaran3105]

I had a multiple choice question that asked when will a galvanic cell stop producing electrical energy?
The two most logical answers were "no ions will be present in the salt bridge" and "the cell reaction will be at equilibrium".
I feel as though both of these answers are correct but the equilibrium answer was the correct one.
Could someone please explain why so?

Thanks!!

[guest123]

I had a multiple choice question that asked when will a galvanic cell stop producing electrical energy?
The two most logical answers were "no ions will be present in the salt bridge" and "the cell reaction will be at equilibrium".
I feel as though both of these answers are correct but the equilibrium answer was the correct one.
Could someone please explain why so?

Thanks!!

There will always be ions in the salt bridge. They just stop migrating after the cells stops producing electrical energy. But they are not the reason that the cell stops so the equilibrium is more correct as it is the reason why the cell stops. The ions just stop migrating as a consequence

[guest123]

I had a multiple choice question that asked when will a galvanic cell stop producing electrical energy?
The two most logical answers were "no ions will be present in the salt bridge" and "the cell reaction will be at equilibrium".
I feel as though both of these answers are correct but the equilibrium answer was the correct one.
Could someone please explain why so?

Thanks!!

There will always be ions in the salt bridge. They just stop migrating after the cells stops producing electrical energy. But they are not the reason that the cell stops so the equilibrium is more correct as it is the reason why the cell stops. The ions just stop migrating as a consequence

[elhoysted]

There will always be ions in the salt bridge. They just stop migrating after the cells stops producing electrical energy. But they are not the reason that the cell stops so the equilibrium is more correct as it is the reason why the cell stops. The ions just stop migrating as a consequence

So we assume ions in the salt bridge are always in excess unless we get extra info?