CSSA chem trial (1 Viewer)

[Enigmatic Eve]

Does anyone know for the multiple choice question, whether we had to find the conjugate acid or conjugate base og HPO4^-??

 

[sig]

pH of H2SO4 is C - 1.6

Diprotic therefore -log[2 x 0.0115] = 1.64


and the conjugate acid one was H2PO4- wasn't it?

 

[Enigmatic Eve]

pH of H2SO4 is C - 1.6

Diprotic therefore -log[2 x 0.0115] = 1.64


and the conjugate acid one was H2PO4- wasn't it?

So the answer is H2PO4-?? I think I got that....
Oh bummer... I got that pH question wrong!!!
Oh well....

 

[Premus]

you guys reckon that they will give 1mark for the equation for that titration question?? haha

 

[xeriphic]

hey sig, lol koo that's the answer I got thanks

 

[Heinz]

pH of H2SO4 is C - 1.6

Diprotic therefore -log[2 x 0.0115] = 1.64

hmm.... I still chose 1.9 knowing full well that it was diprotic. The reason being that the second ionisation stage is in equilibrium, so we cant assume complete ionisation like the first stage. Guess we have to wait.

 

[persephone]

I chose 1.6. I thought they were trying to be tricky. plus I was reading over pH before I got into the exam. I thought I got it right...know you're all scaring me

 

[persephone]

okay this posted twice...i'm just editing it...ignore this....
yeah chem trial...hard

 

[Enigmatic Eve]

hmm.... I still chose 1.9 knowing full well that it was diprotic. The reason being that the second ionisation stage is in equilibrium, so we cant assume complete ionisation like the first stage. Guess we have to wait.

Ooh.. very smart.... I'll use what you said to talk myself out that I got that question wrong.. Lol

 

[sig]

yes under any normal time I would have chosen 1.9

However I've been screwed over by a question like this before over the past papers i've done...the answer assumed it was diprotic so yeah I've always been assuming it ionises to it's fulllest...but then again isn't H2SO4 a strong acid thus it'll ionise completely in water?

 

[Enigmatic Eve]

Yeh... I'm just in denial.. H2SO4 is a strong acid and I believe that it does fully ionise in water.... bummer!! Oh well.. what can I do.... it's over now... more things to worry about

 

[persephone]

you're scaring me...move on to another question....like the standard potential thing....

 

[Enigmatic Eve]

you're scaring me...move on to another question....like the standard potential thing....

I hated that question.. didn't understand what it was going on about... so I made up crap.. hopefully they'll give me at least one mark out of sympathy. Does anyone know the correct answer to the question?

 

[Oz]

yakked on about hydrogen gas and inert Pt electrodes, hopfully got the marks, so annoyed about the sulfer question, read 1% not 0.1% so lost a mark (assuming i got it right in the 1st place that is)

 

[xeriphic]

what was the standard potential question again roughly, as for the inert electrodes question, i wrote the half equation of OH- not sure if it's right, because of NaOH and OH- is preferabily oxidised

 

[Enigmatic Eve]

What was everyone's responses for the AAS (6 mark) question?!
How about the heat of combustion (6 mark) of alkanols question?

 

[withoutaface]

30g = 30 ml (since the Q specifies that 1 ml/g)

therefore the total volume in the flask is 30ml, but 20ml is already occupied by the NaOH solution already in there.

therefore there must be only 10ml of H2SO4 added.

volume ratio is 2:1, mole ratio is 1:2. therefore molarity must be equal.

I believe, however, that the question stated that the scale had already been 'zeroed' with the alkaline solution on it.

 

[Li0n]

hmm.... I still chose 1.9 knowing full well that it was diprotic. The reason being that the second ionisation stage is in equilibrium, so we cant assume complete ionisation like the first stage. Guess we have to wait.

exactly the same as you
CSSA ambigous kings are at it again.
i forgot what the question said exactly but it never mentioned any ionisation stages etc so its either discluded or both are counted, otherwise i have a cry ^_^

 

[jam3s]

Is the history of the acid important, i thought it wasen't so didn't bother remembering it
so i will be happy to get 3 out 6 for that Q
how did every 1 else do on that 1.

 

[withoutaface]

Its a dot point, of course it's important, and you should know by now that those 6-8 markers usually come from history/impact on society type dot points.