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# AS Chemistry- helping each other out! watch

1. Let me know if you'd like me to attach the mark scheme x
2. (Original post by sagzy22)
Can someone please please please give me the May 2014 unit 2 paper??? I desperately need it :'(
I've posted it
3. (Original post by C0balt)
I guess she has mistaken it with other question
Admittedly the multiple choice is hard to mark because they are so packed

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Here idgi
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4. (Original post by Mo_Jo.)
Here idgi

X is the percentage abundance of 10 and there is only 11 so 11 must have abundance of 100-x %
You plug those into formula to find percentage abundance

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Hi guys, Just wondering. For OCR F321, does OCR have a preference for continuous prose in the longer 5/6 mark questions (such as the periodic trends stuff) or are bullet point answers fine? Don't want to lose marks by not writing in the correct style but I prefer bullet points because I find them quicker to write out.
6. Hi could someone explain how you do this please? Thank you

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7. (Original post by TeaAndTextbooks)
Hi could someone explain how you do this please? Thank you

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What exam board? Never seen this type of Q before.
8. (Original post by TeaAndTextbooks)
Hi could someone explain how you do this please? Thank you

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1ppm=1*10^-6
33ppm=33*10^-6 multiply this by 1000g (1kg)

It's similar to percentage. If you were told 20% of a kilogram of a mixture is X, to get x you would multiply a kilogram by 0.2
Percentage is 10^-2
Ppm is 10^-6 that's the only difference
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9. (Original post by _NMcC_)
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Hi guys, Just wondering. For OCR F321, does OCR have a preference for continuous prose in the longer 5/6 mark questions (such as the periodic trends stuff) or are bullet point answers fine? Don't want to lose marks by not writing in the correct style but I prefer bullet points because I find them quicker to write out.
Bullet points are fine. Just make sure they are sentences.
Example:
There are a lot of van der waals forces.
More energy will be required to break these van der waals forces.
So 'inserthere' will have a higher boiling point.

van der waals forces=more energy, so high BP.

Common sense really .
10. Can some tell me what the equation is to work out ISOTOPIC ABUNDANCE ?????
11. (Original post by TheNoobishKnight)
Bullet points are fine. Just make sure they are sentences.
Example:
There are a lot of van der waals forces.
More energy will be required to break these van der waals forces.
So 'inserthere' will have a higher boiling point.

van der waals forces=more energy, so high BP.

Common sense really .
Thanks, Yeah it's not really hard material to understand. You just gotta learn the facts that explain the properties and be able include them them in the answers.

Cheers.

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12. (Original post by FREYA2898)
Can some tell me what the equation is to work out ISOTOPIC ABUNDANCE ?????
Well the equation to calculate relative atomic mass is this
And you can substitute values in to if you are given info and you can do the maths to find unknown

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13. (Original post by C0balt)
Well the equation to calculate relative atomic mass is this
And you can substitute values in to if you are given info and you can do the maths to find unknown

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Not necessarily over a 100 tho
14. (Original post by frozo123)
Not necessarily over a 100 tho
If percentage abundance given then it is

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15. (Original post by TeaAndTextbooks)
Hi could someone explain how you do this please? Thank you

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use this formula so you don't have to think about it

ppm= mass of solute/solution (in grams) x1000,000
16. (Original post by C0balt)
If percentage abundance given then it is

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well yes, however if relative abundance y'know what to do
17. (Original post by C0balt)
Well the equation to calculate relative atomic mass is this
And you can substitute values in to if you are given info and you can do the maths to find unknown

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Hi this is correct if the abundance is a percentage divide by 100 but if it's not a percentage divide by the total abundance
18. (Original post by samwillettsxxx)
Hi this is correct if the abundance is a percentage divide by 100 but if it's not a percentage divide by the total abundance
Well I meant percentage as you can see from the triple %

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19. (Original post by C0balt)
1ppm=1*10^-6
33ppm=33*10^-6 multiply this by 1000g (1kg)

It's similar to percentage. If you were told 20% of a kilogram of a mixture is X, to get x you would multiply a kilogram by 0.2
Percentage is 10^-2
Ppm is 10^-6 that's the only difference
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Thanks, that's what I did

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20. Enthalpy of combustion is reactants - products. I remember it as crp for combustion and fpr for formation. Crp is combustion reactants - products btw.
(Original post by polar0id)
Enthalpy change of combustion = {DeltaH products} - {DeltaH reactants}

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