x Turn on thread page Beta
 You are Here: Home

# AS Chemistry- helping each other out! watch

1. (Original post by Arger)
The first step is to work out the moles:
1.12/56=0.02 - Iron
1.60/16=0.1 - Oxygen

Then divide by the smallest amount to get a ratio:

0.02/0.02=1 - Iron
0.10/0.02=5 - Oxygen

The ratio is 1:5

Therefore we get the formula of Fe05 so A
the mark scheme says d though?
2. (Original post by ilovecake123)
the mark scheme says d though?
Sorry I got it wrong, just realised what I did!

We work out the iron which is 1.12/56=0.02
Then work out the amount of oxygen there is (1.6-1.12)=0.48

0.48/16=0.03

Divide by the smallest amount

0.02/0.02=1
0.03/0.02=1.5

There the ratio is 2:3

So the answer is D Fe203

(sorry for getting it wrong at first, didn't read the question properly
3. (Original post by Arger)
Sorry I got it wrong, just realised what I did!

We work out the iron which is 1.12/56=0.02
Then work out the amount of oxygen there is (1.6-1.12)=0.48

0.48/16=0.03

Divide by the smallest amount

0.02/0.02=1
0.03/0.02=1.5

There the ratio is 2:3

So the answer is D Fe203

(sorry for getting it wrong at first, didn't read the question properly

its fine please can you help me with this question:
11 Oxygen gas, O2, can be converted into ozone, O3, by passing it through an electric
discharge.
3O2(g) 􀁯􀀃 2O3(g)
In an experiment, a volume of 300 cm3 of oxygen was used but only 10% of
the oxygen was converted into ozone. All volumes were measured at the same
temperature and pressure.
The total volume of gas present at the end of the experiment, in cm3, was
A 200
B 210
C 290
D 300
4. (Original post by haemo)
I don't have a copy of the paper on me - our teacher told us our marks and we haven't got it back yet.

That sounds fine, but if you have time available do even more!

I can't see why that wouldn't get you an A though, especially if your notes are correct (from book(s), online resources etc).
Ok ..... thanks for your help but can i ask how you revised ????
5. hey guys!
having a mock tomorrow, need some help with this question
Attached Images

6. (Original post by aigerimk)
hey guys!
having a mock tomorrow, need some help with this question
I haven't studied this topic formally in alevel but I would think the answer is MgO. This is because the forces between the ions are 2+ and 2- which are stronger than 1+ and 1- or two 1+ and one 2+.

Calcium ions are bigger than magnesium ions due to more shells so there is less attraction than a smaller ion such as magnesium. Hopefully this makes sense, google lattice enthalpies for a better explanation.

Posted from TSR Mobile
7. Posted from TSR Mobile
Just did the exam in 2014 as a mock pretty brutal stuff.
8. (Original post by Dylann)
I haven't studied this topic formally in alevel but I would think the answer is MgO. This is because the forces between the ions are 2+ and 2- which are stronger than 1+ and 1- or two 1+ and one 2+.

Calcium ions are bigger than magnesium ions due to more shells so there is less attraction than a smaller ion such as magnesium. Hopefully this makes sense, google lattice enthalpies for a better explanation.

Posted from TSR Mobile
Aah i see thaaaanks
9. Hiya guys! This thread seems useful, i will definitely start using this!

I do Edexcel, and im just wondering what the best definition of a 'covalent bond' is?

Kyle
10. (Original post by haemo)
With AQA, a covalent bond is defined as:

A shared pair of electrons
Okay thank you very much!

I'm also a bit lost as to how you draw a dot and cross diagram for a triple bond, such as N2O (Nitrous Oxide) could anyone please explain?

Thanks alot
Kyle x
11. Has anyone done the salters 2014 paper? Just wondering your opinion on the questions? The few past papers I've done have seemed pretty easy...
12. Posted from TSR Mobile
No ocr
13. (Original post by Niceguayky)
Hiya guys! This thread seems useful, i will definitely start using this!

I do Edexcel, and im just wondering what the best definition of a 'covalent bond' is?

Kyle
For OCR chemistry a shared pair of electrons would get you the mark.

Posted from TSR Mobile
14. How do you explain what determines the shape of a molecule?
I know it's do to with the number of electron pairs/lone pairs around a molecule and lone pairs repel more than bonded pairs, but how do you put that into a comprehensible sentence?

Also, does anyone know how strict examiners are with markings, e.g. if i wrote 'force' instead of 'attraction' or 'large influence of the nucleus on the outer shell electrons' instead of 'greater (nuclear) attraction on (outer) electrons / (outer) shell(s)'.
Basically if I wrote essentially the same thing but a different wording to what appears on the mark scheme. I ask this because some answers in the mark scheme have ORA (or alternative wording) which implies that the ones without ORA have to be exactly the same??

Thanks

For OCR A btw
15. Is a level maths REALLY needed with a level chemistry or will I be taught what I need to know in the chemistry classes
16. (Original post by JohnLE)
Is a level maths REALLY needed with a level chemistry or will I be taught what I need to know in the chemistry classes
GCSE maths will be fine. The maths involved isn't too hard.
17. Right I've got my mock for unit 1 tomorrow should be ready. Any questions would be great
18. (Original post by Super199)
Right I've got my mock for unit 1 tomorrow should be ready. Any questions would be great
ive already done a mock on unit 1 chem....it was june 2014.....a bit of advice make sure you know how to balance equations, bonding (especially metallic, ionic and covalent- like dative ) and KEEP AN EYE ON THE TIME ....i didnt finish mine couz i didnt keep an eye on the time...it literally will go fast!!!!1
19. (Original post by HToo)
ive already done a mock on unit 1 chem....it was june 2014.....a bit of advice make sure you know how to balance equations, bonding (especially metallic, ionic and covalent- like dative ) and KEEP AN EYE ON THE TIME ....i didnt finish mine couz i didnt keep an eye on the time...it literally will go fast!!!!1
AQA?
20. (Original post by Super199)
AQA?
yep aqa

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: July 24, 2017
Today on TSR

### Is uni even worth it?

Does anyone use their degree?

### Can you die from doing this?

Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE