HSC 2012-2015 Chemistry Marathon (archive) (7 Viewers)

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theind1996

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re: HSC Chemistry Marathon Archive

Umm just curious coz I'm kinda wtf-ing, but are both of your questions HSC level?
 

Riproot

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re: HSC Chemistry Marathon Archive

Fixed. But as far as I know it is impossible for there to be those numerical percentages and it meaning mol%, the Carbon - Hydrogen ratio is too high for it to be mol.
But still! It's the principle of the thing.

(It's gravimetric analysis or something, right?)
 

Sy123

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re: HSC Chemistry Marathon Archive

Umm just curious coz I'm kinda wtf-ing, but are both of your questions HSC level?
They are both within syllabus standards not sure what you mean by HSC level.
 

theind1996

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re: HSC Chemistry Marathon Archive

The pH 6 one would be one of the tricky ones but the percentage one is fine. I think we did more of that stuff in year 11 though iirc.
Oh yeah shit.

The empirical formula is from moles shit in Yr 11.

Post some more Production questions guys? I think most people haven't done Acidic in great depth.
 

Sy123

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re: HSC Chemistry Marathon Archive

Oh yeah shit.

The empirical formula is from moles shit in Yr 11.

Post some more Production questions guys? I think most people haven't done Acidic in great depth.
Yeah, I'll post from Module 1 moreso then next time when I need to ask a question.
 

HeroicPandas

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re: HSC Chemistry Marathon Archive

I would tell you why this is not the case, but it would give the answer away haha.

EDIT: I didn't want to kill the thread this early, here is another question in the mean time while people think about it

Upon analysis of mass of a hydrocarbon was found to contain 82.6% Carbon and 17.4% Hydrogen. Calculate its empirical formula
been a while... isnt this preliminary?

C:H

82.6 : 17.4

82.6/12.01 : 17.4/1.008 (Divide by respective atomic masses)

6.87760... : 17.26170...

dIVIDE both sides by 6.87760

1: 2.5

Times both sides by 2

2:5

THerefore EF:

yeh? or am i wrong
 

Sy123

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re: HSC Chemistry Marathon Archive

been a while... isnt this preliminary?

C:H

82.6 : 17.4

82.6/12.01 : 17.4/1.008 (Divide by respective atomic masses)

6.87760... : 17.26170...

dIVIDE both sides by 6.87760

1: 2.5

Times both sides by 2

2:5

THerefore EF:

yeh? or am i wrong
Correct. Now its your turn to post a question (or anyone else can)
 

bleakarcher

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re: HSC Chemistry Marathon Archive

been a while... isnt this preliminary?

C:H

82.6 : 17.4

82.6/12.01 : 17.4/1.008 (Divide by respective atomic masses)

6.87760... : 17.26170...

dIVIDE both sides by 6.87760

1: 2.5

Times both sides by 2

2:5

THerefore EF:

yeh? or am i wrong
I got that too.
 

RealiseNothing

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re: HSC Chemistry Marathon Archive

How is it possible to have NEUTRAL water at ph6?


(just brief and straight to the point)

Something about disassociation, idk exactly since I haven't really started acidic yet.
 

HeroicPandas

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re: HSC Chemistry Marathon Archive

What is the catalyst used in catalytic cracking?

AND

a) Identify 3 properties of the catalyst that makes it useful
b) Describe 2 of them in relation to catalyst cracking (ie. why is this property useful for cat cracking?)

I'm sorry if it sounds weird, i dont know how to word questions xD
 
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bleakarcher

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re: HSC Chemistry Marathon Archive





There is a one to one ratio between HCl and H+


Hence





We get 0.105 from the Volume of the soln which is 105 ml
We now have conecntration of Hydrogen ions, so we take -log of it



I hope I'm right lol

=======================

How is it possible to have NEUTRAL water at ph6?


(just brief and straight to the point)
Maybe this is to do with possible minerals dissolved in the water resulting in an increase in the H+ concentration and thus a decrease in the pH?
 
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bleakarcher

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re: HSC Chemistry Marathon Archive

What is the catalyst used in catalytic cracking?

AND

a) Identify 3 properties of the catalyst that makes it useful
b) Describe 2 of them in relation to catalyst cracking (ie. why is this property useful for cat cracking?)
Properties of zeolite? Shit.
 

DamTameNaken

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re: HSC Chemistry Marathon Archive

For Sy's question about the neutral water with a pH of 6
The equilibrium reaction is H3O+ + OH- <--> 2H20
Is it possible that the conditions are favouring the backward reaction and so you get a solution which has more Hydronium (and conversely more hydroxide) ions than usual.
Of course I'm probably totally wrong, but thought I'd give it a shot.
 

Sy123

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re: HSC Chemistry Marathon Archive

Something about disassociation, idk exactly since I haven't really started acidic yet.
Related to that as well, yes.

Maybe this is to do with possible minerals dissolved in the water resulting in an increase in the H+ concentration and thus a decrease in the pH?
We are looking at pure water here

For Sy's question about the neutral water with a pH of 6
The equilibrium reaction is H3O+ + OH- <--> 2H20
Is it possible that the conditions are favouring the backward reaction and so you get a solution which has more Hydronium (and conversely more hydroxide) ions than usual.
Of course I'm probably totally wrong, but thought I'd give it a shot.
How could the conditions favour the Hydronium ions more?
 

Riproot

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re: HSC Chemistry Marathon Archive

been a while... isnt this preliminary?

C:H

82.6 : 17.4

82.6/12.01 : 17.4/1.008 (Divide by respective atomic masses)

6.87760... : 17.26170...

dIVIDE both sides by 6.87760

1: 2.5

Times both sides by 2

2:5

THerefore EF:

yeh? or am i wrong
Okay, I got this too originally, but how does it make any sense!??!

It would have to be a carbocation which isn't in the HSC syllabus.
 

kazemagic

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re: HSC Chemistry Marathon Archive

been a while... isnt this preliminary?

C:H

82.6 : 17.4

82.6/12.01 : 17.4/1.008 (Divide by respective atomic masses)

6.87760... : 17.26170...

dIVIDE both sides by 6.87760

1: 2.5

Times both sides by 2

2:5

THerefore EF:

yeh? or am i wrong
btw is that important in the HSC?
 

nightweaver066

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re: HSC Chemistry Marathon Archive

Okay, I got this too originally, but how does it make any sense!??!

It would have to be a carbocation which isn't in the HSC syllabus.
It's empirical. Could be which makes sense.
 
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