HSC 2012-2015 Chemistry Marathon (archive) (8 Viewers)

[someth1ng]

re: HSC Chemistry Marathon Archive

I wudve thought D...

The question asks for an ISOMER - not the name of the compound.

 

[Magical Kebab]

re: HSC Chemistry Marathon Archive

But D is the name of the molecule IN the question- for an isomer, it has to be something else. Watch out for this, they often include the name of the molecule shown as one of the options.

Dam didn't even read that bit.

Makes sense now, same molecular formula but different structural.

Shudve read Q properly.

 

[nightweaver066]

re: HSC Chemistry Marathon Archive

Butane has very little to no reactivity with aqueous bromine when mixed together. This is a direct result of the alkane-bromine water mixture not being exposed to any ultra violet light thus preventing drops of added aqueous bromine from being decolourised. Although, the reactivity of 1-butene with bromine water is relatively high in comparison as the alkene does not require the presence of u.v. light to react with bromine water and also because it possesses a double bond which can facilitate the joining of 2 atoms by 'opening up'.

This is evidenced through the addition reaction:

CH3 - CH2 - CH = CH2 + HOBr -----> CH3 - CH2 - CH (connected to the hydroxyl group) - CH2 (connected to Br atom)

I tried

Good attempt, but you should be focusing more on the bonds.

Also, it asks for "structural formulas"

1-butene has a carbon-carbon double bond whereas butane only has carbon-carbon single bonds. Double bonds are much more reactive than single bonds, illustrated by the fact that butane requires UV light to catalyse a substitution reaction with Br2(aq) whereas 1-butene doesn't for an addition reaction with Br2(aq) *insert reactions*.

 

[Aysce]

re: HSC Chemistry Marathon Archive

Good attempt, but you should be focusing more on the bonds.

Also, it asks for "structural formulas"

1-butene has a carbon-carbon double bond whereas butane only has carbon-carbon single bonds. Double bonds are much more reactive than single bonds, illustrated by the fact that butane requires UV light to catalyse a substitution reaction with Br2(aq) whereas 1-butene doesn't for an addition reaction with Br2(aq) *insert reactions*.

Oh my bad about the formulas bit lol and thanks for the feedback

 

[Eg155]

re: HSC Chemistry Marathon Archive

But D is the name of the molecule IN the question- for an isomer, it has to be something else. Watch out for this, they often include the name of the molecule shown as one of the options.

Dam didn't even read that bit.

Makes sense now, same molecular formula but different structural.

Shudve read Q properly.

The question asks for an ISOMER - not the name of the compound.

Lol, thanks guys! I read it as 'name this compound' too. Oh gawsh.

 

[Immortalp00n]

re: HSC Chemistry Marathon Archive

New q:
Coal, containing 0.1% sulfur, is burned in a power station.
Calculate the volume of sulfur dioxide released at 25 degrees and 100 kPa when 10,000,000 kgs of coal is burned.

 

[Omed62]

re: HSC Chemistry Marathon Archive

New q:
Coal, containing 0.1% sulfur, is burned in a power station.
Calculate the volume of sulfur dioxide released at 25 degrees and 100 kPa when 10,000,000 kgs of coal is burned.

sufer is burnt with oxygen in the air:

So S + oxygen ----> Surfer dioxide

n=m/Mm
= 1gram of sulfer burned/32.065= 0.031grams

n=v/Mv

Therefore v= n x Mv = 0.031x 24.79= 0.77 L

Equation: S + O2 ---> SO2

I mole of sufer is equally to 1 mole of SO2, due to molar ratio.

 

[Omed62]

re: HSC Chemistry Marathon Archive

New q:
Coal, containing 0.1% sulfur, is burned in a power station.
Calculate the volume of sulfur dioxide released at 25 degrees and 100 kPa when 10,000,000 kgs of coal is burned.

Her you go lol,

A mole ratio is ratio between the amounts in moles of any two compounds involved in a chemical reaction. Mole ratios are used as conversion factors between products and reactants in many chemistry problems.

For example,

For the reaction:

2 H2(g) + O2(g) → 2 H2O(g)

The mole ratio between O2 and H2O is 1:2. For every 1 mole of O2 used, 2 moles of H2O are formed.

The mole ratio between H2 and H2O is 1:1. For every two moles of H2 used, 2 moles of H2O is formed.

Thus the mole ration of S and SO2 is the same.

 

[someth1ng]

re: HSC Chemistry Marathon Archive

Any further flaming, trolling or abuse will result in infractions or bans.

 

[Omed62]

re: HSC Chemistry Marathon Archive

Any further flaming, trolling or abuse will result in infractions or bans.

Sorry, if you think I am abusing here. But really to be honesty there is some other people who start sorrowing at each other. it would be good if you tell them as well. I am only sorrowing becuase the some people here do not have manners. sorry if you think me worrong but I am not like those who takes bad. I just came here to get some help thats it. you should read the comment about what others say to me, thus I say back. I strongly believe they should get banned because they start say wrong things. I extremely understand you and the BOS rules, that you should all ways respect and help one another but not to talk bad. This is what I strongly believe in. so please dont think me wrong. read all my starting post, I am extremely nice but the people start talking bad.

 

[Magical Kebab]

re: HSC Chemistry Marathon Archive

Sorry, if you think I am abusing here. But really to be honesty there is some other people who start sorrowing at each other. it would be good if you tell them as well. I am only sorrowing becuase the some people here do not have manners. sorry if you think me worrong but I am not like those who takes bad. I just came here to get some help thats it. you should read the comment about what others say to me, thus I say back. I strongly believe they should get banned because they start say wrong things. I extremely understand you and the BOS rules, that you should all ways respect and help one another but not to talk bad. This is what I strongly believe in. so please dont think me wrong. read all my starting post, I am extremely nice but the people start talking bad.

You also have to realise that what you did is wrong, the others were just reacting to that because no one around here does what you do, that is, post questions up hoping people will do your assignment then you also make another account yet post the same questions, in hope that no one will realise whats going on.

 

[someth1ng]

re: HSC Chemistry Marathon Archive

I feel that in either case, all parties are wrong.

It is not a good idea to respond to a heated response with another one - I gave all parties warning/infractions which can lead to temporary bans.

 

[Omed62]

re: HSC Chemistry Marathon Archive

Hey guys please help... how would you answer these in terms of the verb.

1. explain the basic principle of how the electrochemical cell works?

2. Describe lead-acid cell and fuel cell. Assess the impact of lead-acid cell on the development of portable computers and Assess the impact of fuel cell on the development of hybrid cars

3. Evaluate the impact that the development of the electrochemical cell has had on society and the environment.

 

[someth1ng]

re: HSC Chemistry Marathon Archive

Do not re-post your questions.

 

[Eg155]

re: HSC Chemistry Marathon Archive

Assess the use of a biopolymer on society and the environment

 

[Sy123]

re: HSC Chemistry Marathon Archive

 

[bleakarcher]

re: HSC Chemistry Marathon Archive

pH=-log[H+] where log is of base 10.
[H+]=10^(-pH)
=10^(-12) M=10^(-12) mol/L
so that's the hydronium ion concentration of the solution.
Now, at RTP, [OH-]*[H+]=10^(-14)
from that we get [OH-]=10^(-2) M
KOH->K+ + OH-
so [KOH]=[OH-]=10^(-2) M
pH=14-pOH=14+log[OH-]
If pH=13,
log[OH-]=-1
[OH-]=10^(-1) M
=[KOH]
so we need to change the concentration of KOH by 0.09 M and must therefore add 0.09 moles of solid KOH to the solution.

 

[Sy123]

re: HSC Chemistry Marathon Archive

pH=-log[H+] where log is of base 10.
[H+]=10^(-pH)
=10^(-12) M=10^(-12) mol/L
so that's the hydronium ion concentration of the solution.
Now, at RTP, [OH-]*[H+]=10^(-14)
from that we get [OH-]=10^(-2) M
KOH->K+ + OH-
so [KOH]=[OH-]=10^(-2) M
pH=14-pOH=14+log[OH-]
If pH=13,
log[OH-]=-1
[OH-]=10^(-1) M
=[KOH]
so we need to change the concentration of KOH by 0.09 M and must therefore add 0.09 moles of solid KOH to the solution.

Good work:

 

[Aysce]

re: HSC Chemistry Marathon Archive

pH=-log[H+] where log is of base 10.
[H+]=10^(-pH)
=10^(-12) M=10^(-12) mol/L
so that's the hydronium ion concentration of the solution.
Now, at RTP, [OH-]*[H+]=10^(-14)
from that we get [OH-]=10^(-2) M
KOH->K+ + OH-
so [KOH]=[OH-]=10^(-2) M
pH=14-pOH=14+log[OH-]
If pH=13,
log[OH-]=-1
[OH-]=10^(-1) M
=[KOH]
so we need to change the concentration of KOH by 0.09 M and must therefore add 0.09 moles of solid KOH to the solution.

I'm a little unsure with the bolded part and Sy do you make these questions up? I could use a few for practice lol.

 

[Sy123]

re: HSC Chemistry Marathon Archive

I'm a little unsure with the bolded part and Sy do you make these questions up? I could use a few for practice lol.

From what I have seen its harder for me personally to make questions for Chemistry since the numbers need to work in real life (I don't want to associate random numbers to the chemicals)
So at the moment I am just getting these questions from somewhere. But that may change =)