Chemistry aftermath

Lucas10101

I think it's Bomb Calorimeter for 3g. Your equation is right but you need a 2 in front on CH3COOH and in front of the product.

JC 2K3

sean_keevey wrote:

I was waiting for that question. No there wasn't insteadof giving you the specific heat capacity and the mass, they just gave you the product of these i.e. 4200*0.1 and you just had to multiply the figure they gaveee by the change in temperature to get the heat change.

Guess who took it as the specific heat capacity of the HCl, assumed the density to be the same as water and used 0.05 kg as the mass....
(Yes I know the mass was twice that)


3-6 marks gone there....

Thomas_S_Hunterson

JC 2K3 wrote:

Guess who took it as the specific heat capacity of the HCl, assumed the density to be the same as water and used 0.05 kg as the mass....

3-6 marks gone there....

And the department were going out of their way to make it easier for you!!

I think a lot of people may have slipped up there

lemansky

JC 2K3 wrote:

3(g) - I wrote a Thermometor What was it?

5(b) - It said "diagrams", surely you only needed one?

I think its a bomb calorimeter....but i stress that I think that-i'm not sure.

As for the dot and cross bit I did a bohr diagram version with dots and crosses and a normal one with just the letters of the elements, and the electrons from the outer shells if you know what I mean.The s after diagram threw me so I did both!

lemansky

sean_keevey wrote:

It's just potassium iodide, is it not.

Thats what I would've thought.Its what I wrote.

carlowboy

well if you've to learn 40 experiments, the extra marks compared to physics are justified then.

eZe^

I got 2CH3COOH + Na2CO3 ========= 2CH3COONa + H20 + C02

jaydigity

I didn't do Q 10(b), but did we need to get molar voume on the front of the paper to answer it? (you know, that 22.4/24L figure)

Lucas10101

Would you lose marks for putting H2 or something in......it might be part of a product, I think I accidently put it in....

eZe^

jaydigity wrote:

I didn't do Q 10(b), but did we need to get molar voume on the front of the paper to answer it? (you know, that 22.4/24L figure)

I used pv = nrt

JC 2K3

Lucas10101 wrote:

I think it's Bomb Calorimeter for 3g. Your equation is right but you need a 2 in front on CH3COOH and in front of the product.

Ah that's what I did. For some reason I thought it wasn't balanced and was panicking. Sweet.

kisaragi

Exam was fine and fair Sure I could've gotten a good mark if I hadn't developed a severe distaste for chemistry and abandoned it after the mocks

JC 2K3

Oh btw, best question ever:

"How does [ethanol] come to be present in the body?"

lemansky

JC 2K3 wrote:

Oh btw, best question ever:

"How does [ethanol] come to be present in the body?"

Seconded!

cson

My answer > "Drinking skin!" followed meekly by a "consumption of alcoholic beverages"

JC 2K3

I wrote "<insert smart remark here>" and then somethng about ethanol being a recreational drug present in certain beverages.

cookiemonst3r

I loved it!! Thought it was so easy. would have done all the questions but i didnt do question9 cos i didnt want to draw a graph. had enough of those from physics

"Give one reason why carbon dioxide is more easily liquefied than helium."
I thought carbon dioxide sublimes and doesnt change into a liquid!! so confused

And in question 2(f) i wrote NaCH3COOH instead of CH3COOHNa. Does that make a difference??

lemansky

cookiemonst3r wrote:

"Give one reason why carbon dioxide is more easily liquefied than helium."
I thought carbon dioxide sublimes and doesnt change into a liquid!! so confused

And in question 2(f) i wrote NaCH3COOH instead of CH3COOHNa. Does that make a difference??

Ah sure the CO2 thing was only worth 2 out of the 40 or so that you can lose and still get the old A1.
As for the sodium ethanoate I'm not sure.Don't see why it should matter-but I'm probably overlooking something major in saying that.

Thomas_S_Hunterson

cookiemonst3r wrote:

"Give one reason why carbon dioxide is more easily liquefied than helium."
I thought carbon dioxide sublimes and doesnt change into a liquid!! so confused

I just said that it's because Carbon dioxidehas a much higher boiling point. AFAIK helium boils at around 4K so it's not something you'd see as a liquid too often.

JC 2K3

I said that about the boiling point and also that Helium was lighter and had more bias to be a gas.

And cookiemonster, it's CH3COONa, so both of those are wrong I'm afraid...

cookiemonst3r

JC 2K3 wrote:

And cookiemonster, it's CH3COONa, so both of those are wrong I'm afraid...

I actually meant i wrote NaCH3COO

JC 2K3

Ah.

Well I'd say you won't lose all the marks there, maybe one or two.

cocoa

sean_keevey wrote:

Should just be -56.280 kJ

There's no need for a per-mole because it's heat of a specific reaction.

if there's no need of a per-mole then why did you divide by 0.05? (the amount of moles of HCL, and coincidentally of NaOH)

420*6.7/0.05=56280J/mole=5628kJ/mole

cocoa

eZe^ wrote:

[in relation to 10b]
I used pv = nrt

oh yeah, i just kind of asumed they were giving standard temp and pressure...uh oh.. *checks*
hmm, i get 1.08l when i do it that way... I must be doing something wrong because that would be astonishingly unimpressive to say the least...

cson

Definitely a few here that'd be well suitable for coroner......

JC 2K3

cocoa wrote:

oh yeah, i just kind of asumed they were giving standard temp and pressure...uh oh.. *checks*
hmm, i get 1.08l when i do it that way... I must be doing something wrong because that would be astonishingly unimpressive to say the least...

That sounds like the answer I got in the exam.

V = nRT/P

n = m/Mr
n = 2000/44 = 45.45

V = (45.45)(8.3)(290)/(1.01*10^5)
V = 1.083 m^3

It's not that unimpressive, cocoa, you're just using the wrong unit, should be m^3

cocoa

JC 2K3 wrote:

That sounds like the answer I got in the exam.

V = nRT/P

n = m/Mr
n = 2000/44 = 45.45

V = (45.45)(8.3)(290)/(1.01*10^5)
V = 1.083 m^3

It's not that unimpressive, cocoa, you're just using the wrong unit, should be m^3

that would do it... *decides not to bother checking that against my other answer in litres*

Jumping-Jew

Easier than cocoa's mother

pilchard

bryanw wrote:

I wasn't too happy with the exam... I thought some parts of it were difficult and a lot of my weaknesses came up. I suppose I can't be expecting an excellent grade. I'd say C1 tops. I'm a bit disappointed considering all the work I put in since the mocks.

Oh well... at least its all over for me now!!!

i'm feeling more or less the same! But thank god its all over(for me anyway:D )!!!!

cson

Jumping-Jew wrote:

Easier than cocoa's mother

That kind of behaviouris unacceptable jewbag.