HSC Chemistry Question Thread

[RuiAce]

Just a generic question, but for a question on 'Assess the effectiveness of AAS in pollution control', what would be some main points to talk about?

Cheers.

Just compare with how poor historic methods were and how they really wouldn't find many things.

This would mostly be a history based question ending with realising oh wait AAS works miracles.

May be worth mentioning trace elements as well and how AAS helped reveal the presence and impacts of bad stuff like Pb²⁺

[Sssssrr]

for combustion in chemical monitoring, do we need to know about catalytic converters?
thanks

[RuiAce]

for combustion in chemical monitoring, do we need to know about catalytic converters?
thanks

Well I didn't. Maybe you should, but I didn't bother. I just remembered what catalytic cracking was and was like yep.

[kimmie]

If they ask us to draw cellulose, would this be fine?

[JemexR]

Hey for this, I understand it's an exothermic reaction so the answer can be B or D only but how is the answer D? Do we look at the moles or something?


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It's because of the pressure. As the pressure increases, the system will favour the side with less moles on it (Le Chatelier's Principle). B has equal moles of gas on both sides, therefore indicating that if B was the answer, pressure would not influence the yield of product. D is therefore the answer since there is less moles of gas on the side of the products when compared to the reactants, hence the system will favour the forward reaction if the pressure of the system increases.

[JemexR]

If they ask us to draw cellulose, would this be fine?


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I would play it safe and add the carbons -> you have around a minute a mark anyway, so how much extra time will adding a few carbons be? 

[jakesilove]

I would play it safe and add the carbons -> you have around a minute a mark anyway, so how much extra time will adding a few carbons be? 

I definitely agree, I would be drawing the entire molecule

[RuiAce]

If they ask us to draw cellulose, would this be fine?


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Draw the whole thing out with the carbons. It's boring but not hard and things are clearer that way

[onepunchboy]

hello sorry if this is a stupid question, but what are the solubility rules used for? LOL

[RuiAce]

hello sorry if this is a stupid question, but what are the solubility rules used for? LOL

a) To make sure you don't write down wrong states in your equation when things precipitate
b) cation/anion tests

[massive]

guys for equilibrium reactions, do we say: "the change in conditions causes system to adjust and counteract the changes and therefore favour the forward reaction" OR do we say "the change in conditions causes the system to adjust and counteract the changes by shifting the equlibrium to the right"

Also, what affect does increasing the concentration have on the equilibrium if some of the reactant/products are solids or liquids? does it matter??

[RuiAce]

guys for equilibrium reactions, do we say: "the change in conditions causes system to adjust and counteract the changes and therefore favour the forward reaction" OR do we say "the change in conditions causes the system to adjust and counteract the changes by shifting the equlibrium to the right"

Also, what affect does increasing the concentration have on the equilibrium if some of the reactant/products are solids or liquids? does it matter??

The things you said in bold are equivalent; they're both ok. But in either case you must explicitly state the words "Le Chatelier's principle"

Increasing the concentration of solids and liquids do nothing. Because the increase in volume for a solid/liquid counteracts the increase in moles.

[massive]

Because the increase in volume for a solid/liquid counteracts the increase in moles.

Thanks Rui, I get everything except this part, what do you mean??

[RuiAce]

Thanks Rui, I get everything except this part, what do you mean??

In reality too technical and not required for the HSC course. Just take it for granted.

The way I see it, you can't increase the "concentration" of a solid or liquid.

[Cindy2k16]

Hi am i correct in thinking that we only need to know either Zeiglar Natta polymerisation or free radical polymerisation in depth (and just have a simple understanding of the other process? Not both?
TIA