HSC Chemistry Question Thread

[RuiAce]

Divide the energy found in part b by the heat of combustion of hydrogen (convert to KJ)
Then use PV=nRT formula to find the volume of hydrogen

This is not in the HSC chemistry course. Help is always appreciated but unfortunately you need to consider the fact that the HSC chemistry course is dumbed down

[jakesilove]

Another question, can i get help with part C. Regards.

Hey! So, we want to combust Hydrogen gas to produce the same amount of energy. Thus,



Where n is the number of moles. I've also converted the energy into kJ. We can easily solve for n, giving us the required moles of Hydrogen gas. Then, we multiply by the molar volume to get the volume of the gas!

[Cindy2k16]

When a question asks how many isomers a compound has and the structure of the compound is provided, is the number of isomers including the one pictured??  ( and I'm not sure if this has happened but what if only the formula is provided?

[Rikahs]

yeah im pretty sure it's including the picture given.

[RuiAce]

When a question asks how many isomers a compound has and the structure of the compound is provided, is the number of isomers including the one pictured??  ( and I'm not sure if this has happened but what if only the formula is provided?

yeah im pretty sure it's including the picture given.

Can confirm - definite yes to that one

[Cindy2k16]

yeah im pretty sure it's including the picture given.

Can confirm - definite yes to that one

Thanks Turns out the past paper book I have (the yellow book) actually printed the wrong answer and wrongly explained that you don't count the one pictured.

[RuiAce]

Thanks Turns out the past paper book I have (the yellow book) actually printed the wrong answer and wrongly explained that you don't count the one pictured.

Maybe a bit late now (give or take, you can always borrow it from the library) but have you considered Excel Success One?

[Cindy2k16]

Maybe a bit late now (give or take, you can always borrow it from the library) but have you considered Excel Success One?

My chemistry teacher recommended the yellow book so I borrowed it from the library. I'd say that one question is the only issue I've had with it so it's probably fine overall. Besides, I currently have a lot of overdue books from hoarding them for HSC  so borrowing another would be a hassle

[tennis1]

hey guys

does anyone know how to draw the ester from a reaction with a TERTIARY or secondary alcohol and a carboxylic acid? 

And why does a redox primary standard have to be acidified?

Thanks

[jakesilove]

hey guys

does anyone know how to draw the ester from a reaction with a TERTIARY or secondary alcohol and a carboxylic acid? 

And why does a redox primary standard have to be acidified?

Thanks

I have no idea what you even mean by your first question, which just means that it isn't part of the HSC curriculum! So don't worry about it

The redox reaction is acidified with Sulfuric acid, as this acts as a catalyst. Sulfuric acid is a dehydrating agent, removing products in the esterification reaction. By LCP, the equilibrium will shift to the right to make up for that loss, increasing the yield of Ester!

Jake

[tennis1]

I have no idea what you even mean by your first question, which just means that it isn't part of the HSC curriculum! So don't worry about it

The redox reaction is acidified with Sulfuric acid, as this acts as a catalyst. Sulfuric acid is a dehydrating agent, removing products in the esterification reaction. By LCP, the equilibrium will shift to the right to make up for that loss, increasing the yield of Ester!

Jake

thanks Jake
My first q must just be part of the WA curriculum then

[jakesilove]

thanks Jake
My first q must just be part of the WA curriculum then

Ahhh you're a WAer! Sorry, not gonna be able to help you out with that, hope you work out the answer!

[onepunchboy]

hey guys anyone know how to do this q? does the strongest acid mean highest conductivity?  im not sure

thanks

[RuiAce]

hey guys anyone know how to do this q? does the strongest acid mean highest conductivity?  im not sure

thanks

The strongest acid has the highest degree of ionisation.

Weak acids do not have a degree of ionisation of 100% so CH₃COOH is automatically disqualified.

HNO₃ and HCl both have the same degree of ionisation of roughly 100%.

But H₂SO₄ has a degree of ionisation of somewhere around 160%. This is because it is diprotic - the first hydrogen ion fully ionises, and the second is also quite acidic as well.


Hence sulfuric acid is the answer.

[onepunchboy]

Hey another q , just asking to confirm. In q 2 in the multi choice the weak acid required the SAME volume of base to reach equivalence as the strong acid because the student titrated equal conc of 0.1M of acid? However in the graph , because of different concentrations a LARGER volume of base is needed to reach equivalence.

Is this right?
Thanks again