!! HL Chemistry 2015 - discussion, guesses, predictions, explosions, etc.

B4nt3rB0t

Anyone have any ideas?

Deridovely

That new phenylmethanol experiment is almost garaunteed I'd say!

WSG 98

Remember to focus on the guaranteed questions listed at the start of the exam papers.

Know your:
1 Organic Theory
2 Organic Experiments
3 History Of Chem / Trends
4 Volumetric analysis
5 Rates of Rxn
6 Equilibrium
7 The Option

dazzadazza

In the chemistry papers, question 1 is always a titration and question 2 is an organic experiment. Is anyone going to learn all titrations and all the organics and leave out the rest? Is it risky in case they decide to change it this year?

Ima_mokster

I highly doubt they'll change the way the do things this year, they've largely kept to the same routine throughout the years, but the titrations + organic alone count 17 experiments, which is still a huge amount! the remainder aren't too bad. I personally hate titrations

dazzadazza

Ima_mokster wrote: »

I highly doubt they'll change the way the do things this year, they've largely kept to the same routine throughout the years, but the titrations + organic alone count 17 experiments, which is still a huge amount! the remainder aren't too bad. I personally hate titrations

do people often do that. I.e. Study titrations and organic and leave the rest. I haven't heard of anyone else doing it an it makes me wonder.

Ima_mokster

My teacher said he wouldn't recommend it, but understands the logic of it.. the other experiments can come up as part of long questions so will require knowledge of them, but you can always skip that qn.. its up to you at the end of the day! but if you know all the rest you'll be able to answer 2 experiments.

dazzadazza

Ima_mokster wrote: »

My teacher said he wouldn't recommend it, but understands the logic of it.. the other experiments can come up as part of long questions so will require knowledge of them, but you can always skip that qn.. its up to you at the end of the day! but if you know all the rest you'll be able to answer 2 experiments.

I don't know I just feel like it would be a lot less hassle. I mean you could have a fair idea about the rest and properly study the titrations and organic.

shoopdeboop

Well this year is the first that the "Oxidation of Phenylmethanol" experiment is on, and they're fairly likely to ask that (as the organic exp.)

According to my teacher anyway 😜

ko3p

A new Chemistry syllabus is ready to be introduced and will be in the next few years, so don't expect any changes in the layout of the paper.

MF290

I don't have the solution, hoping someone else will give it a shot to compare answers!

Inspector Coptoor

What's the question?

MF290

Inspector Coptoor wrote: »

What's the question?

Was going to post a link of the photo, but it says I'm not able to..... not a able to delete post either!

Magnate

MF290 wrote: »

Was going to post a link of the photo, but it says I'm not able to..... not a able to delete post either!

Just put a few spaces in the url and we can piece it together

AlfaJack

Does anyone know where I can find a full list of experiments for this years exam? Because my friend was saying there's a new experiment (Preparation of benzoic acid) but it's not in my revision book and our teacher never did it with us. I also just want to make sure I have them all covered!
Thank you

owenoneill

There should be a list in the introduction section of your exam papers, or google 'LC Chemistry syllabus'.

Inspector Coptoor

Oxidation of phenyl methanol to benzoic acid is the name of the experiment

d1234

http://www.gillmacmillan.ie/AcuCustom/Sitename/DAM/060/LSMS_Chemistry_Changes_to_the_Experimental_Work.pdf

AlfaJack

Thank you so much

dazzadazza

How does everyone learn chemistry experiments? We haven't done them all. Also I noticed questions in exam papers on experiments that aren't mandatory. (Eg. Sodium Tartate one in the rates of reactions chapter). Do you learn them? There is a new experiment I heard about online but our teacher hasn't mentioned it. Could that come up? I think it's an organic one. I got 78% in my mocks and I feel like the experiments are what's holding me back. I'm looking for an A.

2015lc

dazzadazza wrote: »

How does everyone learn chemistry experiments? We haven't done them all. Also I noticed questions in exam papers on experiments that aren't mandatory. (Eg. Sodium Tartate one in the rates of reactions chapter). Do you learn them? There is a new experiment I heard about online but our teacher hasn't mentioned it. Could that come up? I think it's an organic one. I got 78% in my mocks and I feel like the experiments are what's holding me back. I'm looking for an A.

I think the experiment you're thinking of is the oxidation of phenylmethanol to benzoic acid. It's fairly likely it will come up! I can't post a link but just look it up and there's good explanations

AlfaJack

All about the preparation of benzoic acid is here:
http:// www .gillmacmillan.ie/AcuCustom/Sitename/DAM/060/LSMS_Chemistry_Changes_to_the_Experimental_Work . pdf
(without the gaps)

MmmPancakes

Some parts of the chemistry course confuse me too much, electrolysis especially. It's simple in principle but I can never get my head around the cathode - negative - reduction thing

iCrazzy

Im having some troubles with this qs.
I get how to calculate the moles and grams and how to find x and the percentage.
But how do they get 1.14.
Dont you usually take away the answer u got in grams with the mass given in question to get percentage?

Inspector Coptoor

It says at the start of the question that the crystals of hydrated sodium carbonate weighed 2.5g.
The 1.14g figure is how much of the 2.5g of the crystals is made up of actual sodium carbonate, the remaining mass being the water of crystallisation

Gryffindor

Quick question about the hydrated sodium carbonate question.
When you use the (Va.Ma)/na = (Vb.Mb.)/nb to find the number of moles of base.
Is this the number of moles of sodium carbonate or the hydrated sodium carbonate?

Thanks!

Jason_H

My teacher says Benzoic acid is unlikely to be question 2 as its far too obvious, but could be question 10/11.

She says organic will be loadsa short questions like 2013

DaveMc90

Do you know the way the experiments involving ethanoic acid and ethanal have been taken off the course experimentally , and it does say we still have to know the theory , but does that mean it cant come up in section A but can in section B or can it still come up in section A ?

OMGeary

DaveMc90 wrote: »

Do you know the way the experiments involving ethanoic acid and ethanal have been taken off the course experimentally , and it does say we still have to know the theory , but does that mean it cant come up in section A but can in section B or can it still come up in section A ?

Think it's just Section B

sdio

Gryffindor wrote: »

Quick question about the hydrated sodium carbonate question.
When you use the (Va.Ma)/na = (Vb.Mb.)/nb to find the number of moles of base.
Is this the number of moles of sodium carbonate or the hydrated sodium carbonate?

Thanks!

They are the same thing. 1 mol of hydrated sodium carbonate contains 1 mol of sodium carbonate and x mol of water.

Gryffindor

sdio wrote: »

They are the same thing. 1 mol of hydrated sodium carbonate contains 1 mol of sodium carbonate and x mol of water.

This makes a lot of sense thank you!

iang198

Do we need to know theory on prep of Ethanal and Ethanoic acid or just to test for them??

Gandhai

iang198 wrote:

Do we need to know theory on prep of Ethanal and Ethanoic acid or just to test for them??

i read the syllabus and frm wat i cud make out of it i can almost guarantee that its just the tests

ThatsTheShtuff

My teacher is fairly accurate at predicting (even though i hate the word!),

Ethyne or Esterification for Organic
Iron tablet titration
Test for anions and Flame Tests
WATER!!! (people seem to forget about that, it should definitely be there)
Equilibrium
Rates
Trends/Discoveries/Scientists
Option

FoxScientist

Chemistry: Definitely water theory and probably a water experiment
Also iron tablet titration is apparently a favourite as well as the two new experiments.
Anions and Cations might come up as third experiment either...

MF290

https /imagizer. image shack .us/v2/320xq 90/r/ 661/jZHnOw. jpg

Magnate

MF290 wrote: »

https /imagizer. image shack .us/v2/320xq 90/r/ 661/jZHnOw. jpg

I don't do chemistry but here's the link for anyone who does, https://imagizer.imageshack.us/v2/320xq90/r/661/jZHnOw.jpg

sdio

I got 0.088875 g.

Dianabluex

Chromatography very dued simple marks as well

Gem957

What's your opinion on doing an extra question? Is it worth it or is it a waste of time?

d1234

Think I'll do an extra. Usually I've loads of time over so I suppose it shouldn't impact that much on the others!

expiiplus1

Can you still use sodium dichromate as a test for ethanol (in the yeast experiment) on the biology syllabus if it has been banned for chemistry

sdio

expiiplus1 wrote: »

Can you still use sodium dichromate as a test for ethanol (in the yeast experiment) on the biology syllabus if it has been banned for chemistry

Yes.. the marking scheme accepts either test.

Noire

Anyone have an idea on exactly how strict they are when marking the exams? Like how bad is this negative marking thing ive been hearing about :O

expiiplus1

Not 100% sure about the exact case of chemistry, but negative marking only usually applies if you chance your arm, like if you were asked to state a use of benzoic acid and you gave both "food preservative" and "rocket fuel." The marking can be pretty damn horrid in easy years though. In 2007, they refused to accept "addition reaction" unless you qualified it with "ionic "

Noire

Ah okay I'm mostly worried about the synonyms for words like if the marking schemes said 'make margarine' and I put down 'production of margarine' instead.

OMGeary

What exactly is negative marking ?

Noire

Say a question asks for three points worth three marks each. You put down two which are right and one which is wrong. Instead of getting 6/9 marks you get 3/9 as the wrong answer cancels out the right one

I'm pretty sure that's how it goes but if im wrong someone correct me!

OMGeary

Noire wrote: »

Say a question asks for three points worth three marks each. You put down two which are right and one which is wrong. Instead of getting 6/9 marks you get 3/9 as the wrong answer cancels out the right one

I'm pretty sure that's how it goes but if im wrong someone correct me!

That's encouraging

Blue giant

I think it's more like if you gave four answers and three were correct. You would only get marked correct for two as the wrong answer would cancel out one of the correct ones. I don't think they apply it too often though.

dazzadazza

FoxScientist wrote: »

Chemistry: Definitely water theory and probably a water experiment
Also iron tablet titration is apparently a favourite as well as the two new experiments.
Anions and Cations might come up as third experiment either...

What's the other new experiment? I'm familiar with the oxidation on penylmethanol one.