HSC Chemistry 2017

[kauac]

And I disagree with you when you say burettes are more accurate, because with a burette you can accidentally overpour and not have the miniscus sit where you want it to. With a measuring cylinder, however, you can use droppers to gain the most accurate measurement. I'm not saying that burettes aren't accurate, but they're less accurate than measuring cylinders bc too much can go wrong.

I think that perhaps the hint in the question was the conical flask - typical for a titration. Yes, measuring cylinders can be more practical and accurate to administer small quantities... but when it comes to the context of the question, in a titration, a burette is probably a better option. 

[Merin Thomas]

Predictions of b6?

[Zainbow]

I think that perhaps the hint in the question was the conical flask - typical for a titration. Yes, measuring cylinders can be more practical and accurate to administer small quantities... but when it comes to the context of the question, in a titration, a burette is probably a better option. 

You can't assume it's a titration though, and you can use conical flasks for more than just titrations anyway. And even if it was a titration, out of the options given, measuring cylinder remains the most accurate which is what the question is looking for. I think they only said conical flask to trick students into picking burette

[Em444]

I think the burette/measuring cylinder one is burette, because burettes that hold 30mL are accurate to plus or minus 0.05mL, whereas a measuring cylinder large enough to hold 30mL probably only has 1mL graduations, and doing multiple pours from one with smaller graduations would have a greater chance of error.
But that's a good point about the tap on the burette potentially letting too much out

[Zainbow]

I think the burette/measuring cylinder one is burette, because burettes that hold 30mL are accurate to plus or minus 0.05mL, whereas a measuring cylinder large enough to hold 30mL probably only has 1mL graduations, and doing multiple pours from one with smaller graduations would have a greater chance of error.
But that's a good point about the tap on the burette potentially letting too much out

That's an interesting point, and it's true, some measuring cylinders have graduations that are too close but then again so do some burettes. I don't want to get too deep about this question lol, it remains only question 1, but if you have a burette and a measuring cylinder with equally spaced graduations which will be the most accurate in that case?

[Dante1091]

Hey guys,

I forgot which question it was for but what was the answer to the battery mc question?
I remember that I knew the answer to the dry cell but not the answer to the lead-acid one.

Also would it be ok if I used two equation for the ozone one instead of one?

[Merin Thomas]

Hey what was q 16 and 19? plus for 18 is it 2x <-> y + z?

[Janu383]

What was the answer to the "how much energy is produced if 1kg of CO2 is combusted" question with the ethanol heat of combustion?

[Merin Thomas]

was it in multiple choice or short answer o_o

[angelahchan]

was it in multiple choice or short answer o_o

short answer, 3 marks

[Zainbow]

What was the answer to the "how much energy is produced if 1kg of CO2 is combusted" question with the ethanol heat of combustion?

I can't remember the exact amount but I'm pretty sure I had a 5 digit answer (or maybe 4?) and kJ as my units. Don't think that helps lol

was it in multiple choice or short answer o_o

it was in short answer

[tripat23]

was it about 15 450 kJ ??

[lakwas7]

was it about 15 450 kJ ??

Your answer sounds very familiar!

[Merin Thomas]

I dont know whether its right~
c2h5oh + 3o2 -> 2co2 + 3h2o
But what i did was coverting 1kg into gm and calculating moles of co2. so
1000/12.01+(2x16) = 22.722
so the moles of C2H5OH = 22.722/2 = 11.36 moles
I think (from my memory) it was 1360 KJ/mol.
So H = 1360 x 11.36 = 15451.03 KJ

[Janu383]

Thank you!