MAY11 Chemistry HL Paper 1&2 - TZ2

[Alex1307]

Which one was the chiral diagram?? i think i put b

Yes it was B! I remember this question hehe

[lighthuntz0r]

Which one was the chiral diagram?? i think i put b

second-last question? It was B indeed

What did you guys write for the purification of atimony sulfide (stibnite thingy)?

I wrote something like:

Sb2S3 + 402 = 3SO2 + Sb2O2 and

Sb2O2 + C = 2Sb + C02

But yeah the second equation doesn't seem right, I don't know I'm confused

Actually your first equation is wrong. S and O are in the same oxidation state, so

2Sb2S3 + 902 = 6SO2 + 2Sb2O3 and then

2Sb2O3 + 3C = 4Sb + 3C02

(at least i wrote so)

Edited May 11, 2011 by lighthuntz0r

[iber2011]

What did you guys write for the purification of atimony sulfide (stibnite thingy)?

I wrote something like:

Sb2S3 + 402 = 3SO2 + Sb2O2 and

Sb2O2 + C = 2Sb + C02

But yeah the second equation doesn't seem right, I don't know I'm confused

I put that as well!! I thought i was the only one who got that

[iber2011]

what did you get for the enthalpy question? it was simple but still....were both of the signs of G and T x S negative??

[Joanna C]

hey in paper1 there was a question of SHE...so we had to change the sign of the 2nd equation and then add the values right?? the answer was positive??

I can't remember which equation I changed the sign for, but I got a positive answer which had '48' in it. So maybe 1.48V?

For the multiple choice question about what carries the charge in molten aluminium, was the answer electrons or cations? At first I put electrons, but then I thought they might be testing whether we know ions can move when they're liquid? So I changed it, but now I reckon it might have been electrons again ><

Paper 2 was quite stressful - I knew I'd got the first calculation wrong because it was totally different from the literature value they gave you to work out the percentage error (thank God for them giving the real value though! Wouldn't have realised I'd done it wrong otherwise!) But I decided to move on and come back to it at the end, which was probably a bad idea because it put me in a bad mood for the rest of the paper! In the end I realised I'd used the mass of water instead of copper-what-ever-it-was to find out the moles for the very first question, d'oh! Oh well, all was fine in the end I guess!

[suggaplum]

For the multiple choice question about I think it was Faraday's law, NaCl? and MgCl2 was it B? where the amount deposited of Mg and Cl2 are the same?

Did anyone realise that there were a lot of 'C's in the paper? or is it just me..?

[Joanna C]

For the multiple choice question about I think it was Faraday's law, NaCl? and MgCl2 was it B? where the amount deposited of Mg and Cl2 are the same?

Did anyone realise that there were a lot of 'C's in the paper? or is it just me..?

Yeah, I put that the amount of Mg and Cl2 was the same

[iber2011]

One of the questions i remember i had put low low weak...for something like intermolecular forces....and for the enthalpy question what did you guys put?? both signs were negative?

[Alex1307]

One of the questions i remember i had put low low weak...for something like intermolecular forces....and for the enthalpy question what did you guys put?? both signs were negative?

Ooh the vaporization one? yeah I put weak forces, low boiling point, and low enthalpy of vaporization. I'm not sure though. It might be wrong haha

And for the enthalpy I think it was negative and positive!

Edited May 11, 2011 by Alex1307

[Alex1307]

What did you guys write for the purification of atimony sulfide (stibnite thingy)?

I wrote something like:

Sb2S3 + 402 = 3SO2 + Sb2O2 and

Sb2O2 + C = 2Sb + C02

But yeah the second equation doesn't seem right, I don't know I'm confused

Actually your first equation is wrong. S and O are in the same oxidation state, so

2Sb2S3 + 902 = 6SO2 + 2Sb2O3 and then

2Sb2O3 + 3C = 4Sb + 3C02

(at least i wrote so)

Oh **** I think I got the whole question wrong! And the stupid mass spectrometer question... It was in the November paper so I really thought it wouldn't come up again ugh

I really hope I did good in section B!

Edited May 11, 2011 by Alex1307

[monib]

Question 1 =( ='( ='( just wanna cry =( didn't get it right and was just so confused on SL =( the rest went pretty good

[iber2011]

I remember there was a question about how to test for alkane or alkene...don't exactly remember but what did you guys write??

[Alex1307]

I remember there was a question about how to test for alkane or alkene...don't exactly remember but what did you guys write??

Bromine water!

If it's an alkene, then the water will decolorize (due to the addition reaction of Br2 to alkene to form dibromoalkane).

If it's an alkane, then nothing happens and the bromine water remains red/orange.

[iber2011]

Ok i wrote bromine water yes!! but i don't rememeber for which i wrote brown and which for colorless

You guys remember any other questions?

[Alex1307]

Ok i wrote bromine water yes!! but i don't rememeber for which i wrote brown and which for colorless

You guys remember any other questions?

In question 6, I think, what was the value of Kc? The question was something like: there are 1.50 mol of H2, 1.00 mol of I2 in a 4 dm3 container. At equilibrium there is 1.80 mol of HI.

The equation was H2 + I2 = HI

so I figured that the equilibrium constant was Kc = [HI]2/[H2][i2]

But I'm not sure about the concentration of H2 and I2 at equilibrium. What did you guys write?

[iber2011]

Ok i wrote bromine water yes!! but i don't rememeber for which i wrote brown and which for colorless

You guys remember any other questions?

In question 6, I think, what was the value of Kc? The question was something like: there are 1.50 mol of H2, 1.00 mol of I2 in a 4 dm3 container. At equilibrium there is 1.80 mol of HI.

The equation was H2 + I2 = HI

so I figured that the equilibrium constant was Kc = [HI]2/[H2][i2]

But I'm not sure about the concentration of H2 and I2 at equilibrium. What did you guys write?

Hey yeah the equation was that...or atleast i had put that. I wish i could recall other questions, I have short term memory

I remember this one in paper 2 the box thingy aufbau's principle? how where the arrows? i put all arrows up

[Daedalus]

Ok i wrote bromine water yes!! but i don't rememeber for which i wrote brown and which for colorless

You guys remember any other questions?

In question 6, I think, what was the value of Kc? The question was something like: there are 1.50 mol of H2, 1.00 mol of I2 in a 4 dm3 container. At equilibrium there is 1.80 mol of HI.

The equation was H2 + I2 = HI

so I figured that the equilibrium constant was Kc = [HI]2/[H2][i2]

But I'm not sure about the concentration of H2 and I2 at equilibrium. What did you guys write?

I got something different, because the container was 4 dm3 instead of 1 (in which case you can take the molar values as the concentrations), but come to think it shouldn't make a difference, since you're using ratios anyway. Both of your upper equations were fine, except h2 + 12 makes 2HI. Essentially you do an ICE diagram -- initial, change, equilibrium.

Here is a quick picture from excel:

So whether or not you adjusted for concentrations you should have got the same value. I'm not sure if the initial values of H2 and I2 are correct - can't remember, physics has chased everything else out of my brain - but if they are then I think my calculations should be okay.

Otherwise... I screwed up enthalpies, I think the magnitude was 73 or 63 maybe as I've heard that a couple of times.. thought it was okay though. Hard to tell overall to be honest - could be a high 5 or a low 7. Paper 1 especially is just mysterious to me in terms of what I think I'm gonna get.

[Alex1307]

Hey yeah the equation was that...or atleast i had put that. I wish i could recall other questions, I have short term memory

I remember this one in paper 2 the box thingy aufbau's principle? how where the arrows? i put all arrows up

I put one arrow up and one down in the 4s orbital and 4 arrows up in the 3d orbital... haha I'm not sure about that

Edited May 12, 2011 by Alex1307

[Alex1307]

Ok i wrote bromine water yes!! but i don't rememeber for which i wrote brown and which for colorless

You guys remember any other questions?

In question 6, I think, what was the value of Kc? The question was something like: there are 1.50 mol of H2, 1.00 mol of I2 in a 4 dm3 container. At equilibrium there is 1.80 mol of HI.

The equation was H2 + I2 = HI

so I figured that the equilibrium constant was Kc = [HI]2/[H2][i2]

But I'm not sure about the concentration of H2 and I2 at equilibrium. What did you guys write?

I got something different, because the container was 4 dm3 instead of 1 (in which case you can take the molar values as the concentrations), but come to think it shouldn't make a difference, since you're using ratios anyway. Both of your upper equations were fine, except h2 + 12 makes 2HI. Essentially you do an ICE diagram -- initial, change, equilibrium.

Here is a quick picture from excel:

So whether or not you adjusted for concentrations you should have got the same value. I'm not sure if the initial values of H2 and I2 are correct - can't remember, physics has chased everything else out of my brain - but if they are then I think my calculations should be okay.

OKAY GOOD THAT'S EXACTLY WHAT I DID

Well I got Kc = 52 but it's close enough

Otherwise... I screwed up enthalpies, I think the magnitude was 73 or 63 maybe as I've heard that a couple of times.. thought it was okay though. Hard to tell overall to be honest - could be a high 5 or a low 7. Paper 1 especially is just mysterious to me in terms of what I think I'm gonna get.

I totally agree. I feel like I did good in paper 1 but there's really no way to be 100% sure. Paper 1 can be super tricky sometimes.

Edited May 12, 2011 by Alex1307

[Alex Hook]

I remember there was a question about how to test for alkane or alkene...don't exactly remember but what did you guys write??

Bromine water!

If it's an alkene, then the water will decolorize (due to the addition reaction of Br2 to alkene to form dibromoalkane).

If it's an alkane, then nothing happens and the bromine water remains red/orange.

i put the other way around