Chemistry 2014 Predictions?

[skybluemaniac]

Hey guys! the exam is almost upon us!

Since there was a massive enzyme and electrolysis question last year is it reasonable to expect that those areas won't be tested as much? Not that I'm not studying for those sections (actually those are my best areas).

Also what else wasn't tested last year? That would be likely to come up yeah?

[Reus]

Hey guys! the exam is almost upon us!

Since there was a massive enzyme and electrolysis question last year is it reasonable to expect that those areas won't be tested as much? Not that I'm not studying for those sections (actually those are my best areas).

Also what else wasn't tested last year? That would be likely to come up yeah?

I hope there's a section on DNA and proteins 

[skybluemaniac]

I hope there's a section on DNA and proteins 

They were a bitch on marking the secondary structure of protein question last year. you couldn't simply say Hydrogen bonding then pleating and coiling. had to talk about the oxygen on one side bonding with a hydrogen on the other side. Like that's super specific for two marks

[Edward21]

They were a bitch on marking the secondary structure of protein question last year. you couldn't simply say Hydrogen bonding then pleating and coiling. had to talk about the oxygen on one side bonding with a hydrogen on the other side. Like that's super specific for two marks

Hahhaha yup!! I drew out a diagram of hydrogen bonding to ensure I got the marks 

[All†Fiction]

A strong acid has a conjugate base that is unbelievably weak, so weak that it barely even accepts protons (eg. HCl is a strong acid, but when was the last time you've heard of a solution of NaCl causing the pH of a solution to rise?)

A weak acid has a conjugate base that is weak - but not unbelievably weak. CH3COOH is a weak acid, and CH3COO- is a weak base.

Analogy:

HCl is a married couple with H+ and Cl-. H+ (the guy) and Cl- (the girl) have been married for 20 years. Married in name only. Cl- is not a particularly easy person to get along with, she's quite an unpleasant character. So when you dunk HCl in water, there's a lot of O(2-) ions (other girls) that makes H+'s eyes go O.O. On the down side, there are already two damned guys (H+'s) with each girl - hence why it's H2O. So, at the first opportunity, H+ divorces Cl- and has the time of his life with his...rendevous...with the O(2-)'s, joining the other two H+s to form H3O+

Meanwhile, Cl-, her husband having just left her, tries to find another man. But she finds that no man is interested in her because she's such an unpleasant character; the men would rather be with the O(2-)'s.

In contrast...

CH3COOH is a relatively ok married couple. They have their ups and downs. H+ likes CH3COO-, she's quite nice, but H+ wishes he can have a few on the side. So when CH3COOH enters water...some of the H+ goes "ah, there are some nice looking girls over there each with two men" and then they leave the CH3COO-.

The CH3COO-, being nice enough, manages to attract her ex-husband back, to form CH3COOH again. But the husband cheats on her again and leaves, and comes back again, and leaves...etc. There's a reversible reaction. CH3COOH is a weak acid and CH3COO- is a weak base, but a reasonable base.

Yet in contrast...

H2 is the happiest married couple with H+ adoring the lovely, amazing, beautiful H-. So when you dunk H2 in water...the H+ will see the O(2-) each with two men (to form H2O) and will be like "huh, why do I need those girls when I have my H- babe". So it's impossible to separate these two.

But suppose you dunk H- in water...

When she enters the water, all the H+ who are frolicking with the O(2-)s will turn their heads and stare at her longingly. Before long, they rush away from their O(2-)s and savagely compete for the H-. Eventually, you end up with happily married H2, and some of the O(2-)s only having one man (to form OH-). And that's why H- is a strong base.

A ridiculously unbelievably weak acid like H2 will have a strong conjugate base like H-.

Hope this makes sense...!

Wow, this is awesome, thank you so much!

[Edward21]

You probably already know that this but goes, this year's paper has 12 questions and is 45 pages... much longer than 2013!!

[Reus]

You probably already know that this but goes, this year's paper has 12 questions and is 45 pages... much longer than 2013!!

seriously sucks!! hopefully its just a lot of graphs, blank pages and diagrams

[skybluemaniac]

Hahhaha yup!! I drew out a diagram of hydrogen bonding to ensure I got the marks 

how did you draw it? did you draw two amino acids?

[Blondie21]

You probably already know that this but goes, this year's paper has 12 questions and is 45 pages... much longer than 2013!!

this is why I'm planning to being with Section B in the exam (despite always doing MC in previous practice exams)... I feel like they've made this exam so long so that many students will be unable to finish it.

any more last minute tips? like the one about the pH curves (thanks so much for that btw!!!! )