**Chemistry...Before/After

ei.sderob

finality wrote: »

I don't think you're supposed to multiply by 2. Is this question 1? You're told it's a 0.05 molar solution - that's 0.05 moles per litre. It doesn't matter that you've only made 500cm^3 of it as it's still a 0.05 molar solution.

Even if you got the moles per litre wrong, you'd still get the marks for the grams per litre provided your work for that part of the question was correct.

Do you divide the .05 by 2 when finding the mass of Na2CO3 or what's the deal with that??

FaoiSin

Yeah I made a mistake by getting it in 500cm^3 instead of one litre. Hopefully won't lose that many marks. Confident I got the rest of the paper right anyway. Can't believe I didn't spot it.

ChemHickey

ei.sderob wrote: »

I can NEVER find the time to do extra questions in Chem exams! Are you doing something with Chemistry in college? Just going by your name like...

I'll be doing Math Science in Galway which involves chemistry in the first two years so ya, kinda... Kinda tempted to do a postgrad in chem though... just love it. I had time to do the water question too! But I decided against it as I said I'd reread the paper instead! Good thing I did as I saw the titration figures had to be to 2 decimal places... Phewwww.

ShaunaMoll

Anyone know what the other pair of structural isomers were in the reaction scheme in Q8?

Think I said Propanal and Propanone but it was a total guess!

Hayezer

Organic was great, think I may have gotten 50/50 if I remember correctly. Did 10 questions, hopefully I'll get a B3 or B2?

ChemHickey

ei.sderob wrote: »

Do you divide the .05 by 2 when finding the mass of Na2CO3 or what's the deal with that??

I think the OP of that question forgot to put n=2 for HCL, he/she had it at n=1 and then when cross multiplying, there was no x2 on the RHS

finality

ei.sderob wrote: »

Do you divide the .05 by 2 when finding the mass of Na2CO3 or what's the deal with that??

Yeah. You do, I THINK I did in the exam...hopefully :L

ChemHickey

ShaunaMoll wrote: »

Anyone know what the other pair of structural isomers were in the reaction scheme in Q8?

Think I said Propanal and Propanone but it was a total guess!

CORRECT!

ei.sderob

I'm not sure if I saw the "to two decimal places"....I hope I have. This will eat away at me now!!!:P

ShaunaMoll

ChemHickey wrote: »

CORRECT!

Oh THANK GOD. Love organic and it nearly killed me thinking that I got that part wrong!

Hayezer

Whats volatile liquid that you used? I said propanone

And there was question about pressure or something, cant remember it? What was answer :L?

finality

ei.sderob wrote: »

I'm not sure if I saw the "to two decimal places"....I hope I have. This will eat away at me now!!!:P

I can't remember if I did either. I usually leave things to 2 decimal places, sincerely hoping that question wasn't the one exception :L

abbeymate

Sorry everyone, I thought that you were supposed to multiply by 2 because it was 500 cm^3 but that I forgot.. So I did divide by 2 because it was 2:1 and I got 0.1202 M/L for moles per litre and I multiplied 0.1202 by 36.5 (Mr of HCl) to get 4.3873 g/L.. How does that sound? And thanks everyone for your help!

Mista

Hayezer wrote: »

Whats volatile liquid that you used? I said propanone

And there was question about pressure or something, cant remember it? What was answer :L?

I used that too

I think it was how do you know the pressure is the same as atmospheric pressure? I said something along the lines of excess pressure/vapour escapng though the pinhole :L

ei.sderob

finality wrote: »

I can't remember if I did either. I usually leave things to 2 decimal places, sincerely hoping that question wasn't the one exception :L

I hate how this site makes you doubt yourself!

leaveiton

Right, from this thread I don't think I got a single calculation other than the heat of formation one right :pac: Ah well, didn't want those marks anyway.

finality

abbeymate wrote: »

Sorry everyone, I thought that you were supposed to multiply by 2 because it was 500 cm^3 but that I forgot.. So I did divide by 2 because it was 2:1 and I got 0.1202 M/L for moles per litre and I multiplied 0.1202 by 36.5 (Mr of HCl) to get 4.3873 g/L.. How does that sound? And thanks everyone for your help!

Pretty sure that's correct, though...it should've been to two decimal places :P

Mista wrote: »

I used that too

I think it was how do you know the pressure is the same as atmospheric pressure? I said something along the lines of excess pressure/vapour escapng though the pinhole :L

That's what I said too.

ei.sderob

abbeymate wrote: »

Sorry everyone, I thought that you were supposed to multiply by 2 because it was 500 cm^3 but that I forgot.. So I did divide by 2 because it was 2:1 and I got 0.1202 M/L for moles per litre and I multiplied 0.1202 by 36.5 (Mr of HCl) to get 4.3873 g/L.. How does that sound? And thanks everyone for your help!

Think that's right! I THINK.

kaet

Sorry to bring it up again, but I don't think it was solved earlier and it's killing me.. For the equilibrium question did it have to be inverted or anything or was it just a really big Kc? I got 704.95 I think.

abbeymate

finality wrote: »

abbeymate wrote: »

Sorry everyone, I thought that you were supposed to multiply by 2 because it was 500 cm^3 but that I forgot.. So I did divide by 2 because it was 2:1 and I got 0.1202 M/L for moles per litre and I multiplied 0.1202 by 36.5 (Mr of HCl) to get 4.3873 g/L.. How does that sound? And thanks everyone for your help!

Pretty sure that's correct, though...it should've been to two decimal places :P

CRAP CRAP CRAP!! Cant believe I got this far and to be deducted for such stupidity!! Wonder will they disallow my answers?? Please God let ne have a decent examiner!! ;-)

ShaunaMoll

Yellowstars wrote: »

what did ye say for Q7 problems arising after adding too much of fluorin or chlorine(there the ones i chose). oh and q8 9(e) the reagent and catalyst to bring about conversion R. and the instantaneous rate at 60 seconds? aaaand 4e.the oxidation/reduction balance?

actually, for the oxidation/reduction balance, I just got a 2 in front of the H+ on the left hand side, seemed weird but I couldn't see another way?

Mista

abbeymate wrote: »

finality wrote: »

Pretty sure that's correct, though...it should've been to two decimal places :P

CRAP CRAP CRAP!! Cant believe I got this far and to be deducted for such stupidity!! Wonder will they disallow my answers?? Please God let ne have a decent examiner!! ;-)

Nooo lol, you'll lose like 1 mark at most :P

finality

kaet wrote: »

Sorry to bring it up again, but I don't think it was solved earlier and it's killing me.. For the equilibrium question did it have to be inverted or anything or was it just a really big Kc? I got 704.95 I think.

That's what I got and so far I haven't been convinced that it's wrong or right. :L

RedTexan

kaet wrote: »

Sorry to bring it up again, but I don't think it was solved earlier and it's killing me.. For the equilibrium question did it have to be inverted or anything or was it just a really big Kc? I got 704.95 I think.

why would it have to be inverted?

ShaunaMoll

kaet wrote: »

Sorry to bring it up again, but I don't think it was solved earlier and it's killing me.. For the equilibrium question did it have to be inverted or anything or was it just a really big Kc? I got 704.95 I think.

I got the same! I don't see why it'd have to be inverted? I've only ever inverted when it was a question where you were given KC and you had to use x's? This seemed like a straight forward equil. question. I'm really doubting myself now, arrrrgh!!

kyle84

id be so gutted if i didn't get my A1,i love chem so much. I was actually lookin forward to the exam. Questions 1 and 2 were ok,4 was grand,5,6,7 were very fun..i messed up rates-possibly the easiest question in everyone's opinion :L and i think i messed up sumtin in acids and bases,so overall it shud b ok.

finality

RedTexan wrote: »

why would it have to be inverted?

Some guy was saying that because the top arrow was pointing backwards you had to reverse the reaction and invert Kc. I disagree but he seemed quite adamant about it (and patronising).

ChemHickey

finality wrote: »

Some guy was saying that because the top arrow was pointing backwards you had to reverse the reaction and invert Kc. I disagree but he seemed quite adamant about it (and patronising).

The top arrow was pointing backwards?


It's bloody equilibrium! :L Of course there are two arrows! :L

Rebels101

would propan-1-ol and propan-2-ol be isomers aswell as propan=2=ol was alcohol a?

abbeymate

Mista wrote: »

abbeymate wrote: »

finality wrote: »

Pretty sure that's correct, though...it should've been to two decimal places :P

CRAP CRAP CRAP!! Cant believe I got this far and to be deducted for such stupidity!! Wonder will they disallow my answers?? Please God let ne have a decent examiner!! ;-)

Nooo lol, you'll lose like 1 mark at most :P

Ok... Thanks everyone im gonna stop checking up all the answers now before it drives me insane!! Was hoping for an A1 but would be happy with an A2 now, so many silly little mistakes :'( :L

ShaunaMoll

finality wrote: »

Some guy was saying that because the top arrow was pointing backwards you had to reverse the reaction and invert Kc. I disagree but he seemed quite adamant about it (and patronising).

Ugh, that's the first time i've ever seen the top arrow pointing backwards! Would they really be that mean? Could be a missprint?...please let it be a missprint..

kyle84

i dont like equilibrium but the position of the arrows sounds fairly irrelevant. A value of 704 sounds very high but then again it seems to be popular so its prob right

finality

ChemHickey wrote: »

The top arrow was pointing backwards?


It's bloody equilibrium! :L Of course there are two arrows! :L

I'm glad I'm not alone in this. It scared me

FaoiSin

Oh god. It's going backwards... 18 marks

RedTexan

finality wrote: »

Some guy was saying that because the top arrow was pointing backwards you had to reverse the reaction and invert Kc. I disagree but he seemed quite adamant about it (and patronising).

That's his logic? I think he might have been reading into it a little too much. The position of the arrows is most definitely irrelevant

RedTexan

finality wrote: »

Some guy was saying that because the top arrow was pointing backwards you had to reverse the reaction and invert Kc. I disagree but he seemed quite adamant about it (and patronising).

That's his logic? I think he might have been reading into it a little too much. The position of the arrows is most definitely irrelevant

kyle84

if it was going backwards tho you would invert kc,don't know if it is though

Hayezer

Doesn't every equilibrium question have a forward and backwards arrow? It's a reversible reaction.

TMCGY

RedTexan wrote: »

That's his logic? I think he might have been reading into it a little too much. The position of the arrows is most definitely irrelevant

Yea sure the arrows just tell you that the reaction is going forwards and backwards isnt it?? Makes no diff which way they go?

Yellowstars

would you get any marks if you said propanone and propan-1-ol were isomers? i know propan1ol isnt,but just cos i said propanone? haha i know im being picky. also do esters have a fruity smell? delighted with q6 did ye get -224?? was there O2 in the equation for its formation ?

ShaunaMoll

It sounds like noone factored in this backwards arrow so they'll hardly mark us hard on it?

RedTexan

And if you look at the question about the indicator and it's equilibrium, the arrows are in the same way?

leaveiton

Surely it doesn't make a difference, there's still a forward reaction and a backwards reaction?

finality

RedTexan wrote: »

And if you look at the question about the indicator and it's equilibrium, the arrows are in the same way?

Exactly, that's what I was saying. That exact indicator equation is in chemistry live with the reactants and products at the same sides, but with the arrows going the normal way.

kyle84

id just stop worrying about it,everyone's probably ok. Any1 else enjoy the water question?

Mista

kyle84 wrote: »

id just stop worrying about it,everyone's probably ok. Any1 else enjoy the water question?

Yes It was fantastic...

ivanh

ChemHickey wrote: »

The top arrow was pointing backwards?


It's bloody equilibrium! :L Of course there are two arrows! :L

Never mind him, it doesn't matter what way the arrows point - the left hand side of any chemical equation is the reactants and the right is the products!

FaoiSin

kyle84 wrote: »

id just stop worrying about it,everyone's probably ok. Any1 else enjoy the water question?

I enjoyed all of the questions apart from the experiments tbh Water was a nice one. Organic was gorgeous. Shorts were nice and simple and Rutherford popped up as expected.

ivanh

What did ye say for the structural isomers?

I said Propanone and Propanoic acid cause if you count all the C's H's and O's they have the same number of each

ivanh

What did ye say for the structural isomers?

I said Propanone and Propanoic acid cause if you count all the C's H's and O's they have the same number of each