CSSA chemistry (3 Viewers)

[umz93]

Re: CSSA Chemistry 2011

Fucking hell, that's two marks I've gotten. Lol

Did you write the weight?

 

[jamesfirst]

Re: CSSA Chemistry 2011

Yes thats what i put! alot of kids in my school said it was by fractions of crude oil...

I nearly did that. But I said to myself... NAHHHHHHHHHHHHHHHHHH sif. So I did the cracking of alkane. It sounds more chemistry. lol

 

[_deloso]

Re: CSSA Chemistry 2011

sulfuric acid had more h+ and lower pH because it can partially dissociate another h+ ion.

sulfuric acide had more H in comparison with HCl however, its initial concentration was 0.25 thus sulfuric acid completely dissociates (strong acid) into 2 H+ ions. therefore, the concentration of H+ is 0.25 x 2 = 0.50 M This is the same as HCl as HCl dissociates into one H+ and its concentration will be 0.50 M. This also mean that both have the same pH as it has equal H+ concentration.

 

[jamesfirst]

Re: CSSA Chemistry 2011

What was your answer for the HCl being added to BaOH and the resulting pH of the solution.

I put A for this. 4. something. wait was it 4.something ??

Also what was the answer of what is the use of the Geiger counter.

Used to check the metal defect or something. I remembered from industrial use of cobalt 60

And just a checking thing: in MCs there was a question comparing sulfuric acid and HCl - my answer was they have the same H+ and the same pH. Is that what you got?

Yeah I did same pH. I thought h2so4 would ionise more protons since it was diprotic. But only one answer in the MC had the same pH. So I just chose that one.

 

[_deloso]

Re: CSSA Chemistry 2011

Did you get the HCl + BaOH question? MC.

remind me what the question was. but yeah I think I kind remember..

 

[umz93]

Re: CSSA Chemistry 2011

I put A for this. 4. something. wait was it 4.something ??





Used to check the metal defect or something. I remembered from industrial use of cobalt 60




Yeah I did same pH. I thought h2so4 would ionise more protons since it was diprotic. But only one answer in the MC had the same pH. So I just chose that one.

Was it A cos i think thats what i put

 

[Dylanamali]

Re: CSSA Chemistry 2011

Hmm yeah I put A it was 0.40 or something rather.. however my calculated answer was like 0.45, which worried me abit...

Yeah I understand that cobalt 60 is used to check for metal defects.. but how is a Geiger counter related.. =/, Geiger counter's just detect radiation, they themselves cant check metal defects =/



Used to check the metal defect or something. I remembered from industrial use of cobalt 60




Yeah I did same pH. I thought h2so4 would ionise more protons since it was diprotic. But only one answer in the MC had the same pH. So I just chose that one.[/QUOTE]

 

[jamesfirst]

Re: CSSA Chemistry 2011

Yeah stupid industrial

Apparently you could talk about decarbonating soft drinks. But I did this weird experiment in school.


Does this equation make sense:


H2O <-> H2O ?

 

[Dylanamali]

Re: CSSA Chemistry 2011

remind me what the question was. but yeah I think I kind remember..

I don't remember the specifics but it was a MC question... a certain volume and certain conc of HCl was added to a certain volume and certain conc of BaOH. I worked out the no. of mols of each, found which one was in excess.. which was the HCl - calculate the no. of mols of excess and then divided it by the volume 0.035 i think it was (25mL + 10mL) and the did -log of that answer.. I ended up getting like 0.45 something but the answer on the multiple choice was like 0.40

 

[jamesfirst]

Re: CSSA Chemistry 2011

hahaha..

Did anyone get tricked by the Nuclear chemistry question... The one where you had to fill in what A and B were. I got Krypton-(forgot the weight) and Barium- (forgot the weight)

OMG I nearly fucking owned myself.


I put germanium and barium. Lucky I double checked it...

 

[umz93]

Re: CSSA Chemistry 2011

R U SRS! NOOOOOOOO! i could have done that easily FML

 

[jamesfirst]

Re: CSSA Chemistry 2011

It was Barium and Krypton but I don't think you can right just barium and krypton coz they are isotopes so you have to write the weight after each, e.g. Cobalt-60 .

sif. The mass number was given in the Q.

 

[Dylanamali]

Re: CSSA Chemistry 2011

Apparently you could talk about decarbonating soft drinks. But I did this weird experiment in school.


Does this equation make sense:


H2O <-> H2O ?

umm water is in an equilibrium with water???
The best way to demonstrate equilibrium is the Fe3+ + SCN- -> FeSCN2-
as they each have diff colours..

unless it was testing the other experiment, e.g. modelling an eqm reaction, which would be using two diff sized pipettes and constantly transfering water.

 

[jamesfirst]

Re: CSSA Chemistry 2011

Hmm yeah I put A it was 0.40 or something rather.. however my calculated answer was like 0.45, which worried me abit....

[/QUOTE]

same. I got a diff value but I just chose A cos it was the closest

 

[Dylanamali]

Re: CSSA Chemistry 2011

sif. The mass number was given in the Q.

hmm I guess your right.. Coz it said just find out what A and B was so I guess you could just right the symbols Kr and Ba

 

[Dylanamali]

Re: CSSA Chemistry 2011

same. I got a diff value but I just chose A cos it was the closest[/QUOTE]

ok cool, preety dodgy question but.. if there was no correct answer =/ i was worried haha

 

[_deloso]

Re: CSSA Chemistry 2011

I don't remember the specifics but it was a MC question... a certain volume and certain conc of HCl was added to a certain volume and certain conc of BaOH. I worked out the no. of mols of each, found which one was in excess.. which was the HCl - calculate the no. of mols of excess and then divided it by the volume 0.035 i think it was (25mL + 10mL) and the did -log of that answer.. I ended up getting like 0.45 something but the answer on the multiple choice was like 0.40

hmmm sorry cant remember exactly what my answer was but yeah I subtracted one of the excess volume from the other as it neutralises and yeah divided it by the total volume. not quite sure what my answer was though. sorry

 

[jamesfirst]

Re: CSSA Chemistry 2011

umm water is in an equilibrium with water???
The best way to demonstrate equilibrium is the Fe3+ + SCN- -> FeSCN2-
as they each have diff colours..

unless it was testing the other experiment, e.g. modelling an eqm reaction, which would be using two diff sized pipettes and constantly transfering water.

cos we did this experiment where we got 2 measuring cylinders and filled 1 with water. We then got a pipette to transfer the water into the second cylinder. Then we transfered the water from the 2nd cylinder back into the first one. We repeated this until there was no change in volume.

 

[Riproot]

haha fair enough, my mistake then =).
Ahh careless error then, just had to get my volume and minus from the origin. Did you use C1V1 = C2V2?

lol no. I used something really complicated that probably didn't work out right. Our teacher kinda let's us do our own maths things because 80% of the class does mx1. So I kinda don't know if I got it right. :/

Did you write the weight?

yeah brah. I was like "I won't need this but I'll write it anyways."

sulfuric acide had more H in comparison with HCl however, its initial concentration was 0.25 thus sulfuric acid completely dissociates (strong acid) into 2 H+ ions. therefore, the concentration of H+ is 0.25 x 2 = 0.50 M This is the same as HCl as HCl dissociates into one H+ and its concentration will be 0.50 M. This also mean that both have the same pH as it has equal H+ concentration.

that's wrong. Sulphuric acid only partially dissociates the second h+ ion.

 

[jamesfirst]

Re: CSSA Chemistry 2011

The only question I'm worried about is the ethanol and octane question. I think I fked up the radioisotope in medicine. I did Tc-99m and said that the problem was the short half life. Hence, it is produced in hospitals. Is this correct ??? lol