OCR Chemistry B (Salters) Thursday 10th January Discussion

Reply 60

Tikara

great

, is a dative covalent bond formed in nucleophilic substitution with the nucleophile?

Reply 61

Tikara

Original post by Tikara

great

, is a dative covalent bond formed in nucleophilic substitution with the nucleophile?

yes it is haha just found out

Reply 62

buzzing22

does anybody know the formula to work out gas volumes?!

Reply 63

Coombsy

10

Original post by buzzing22

does anybody know the formula to work out gas volumes?!

Number of Moles = Volume (dm³) / 24
Or
Number of Moles = Volume (cm³) / 24000

1dm³=1000cm³

(edited 11 years ago)

Reply 64

Welbeck

3

Hi, I am studying with OCR B salters and got 1 mark from an A* in chemistry last year in triple science.
I've done my revision and now just doing lots of past papers.
I don't get how all of the hess's law works (enthalpy of reaction, combustion and formation) and how you construct them and what goes at the bottom.
Also has anyone got the june 2012 paper? I can't seem to find it anywhere!
And good luck guys !

Reply 65

krisshP

14

Original post by Welbeck

Hi, I am studying with OCR B salters and got 1 mark from an A* in chemistry last year in triple science.
I've done my revision and now just doing lots of past papers.
I don't get how all of the hess's law works (enthalpy of reaction, combustion and formation) and how you construct them and what goes at the bottom.
Also has anyone got the june 2012 paper? I can't seem to find it anywhere!
And good luck guys !

Get the following book
http://www.amazon.co.uk/Calculations-AS-A-Level-Chemistry/dp/0582411270/ref=sr_1_1?ie=UTF8&qid=1357384204&sr=8-1

You can NOT ask for that paper.

Reply 66

Coombsy

10

Original post by Welbeck

Hi, I am studying with OCR B salters and got 1 mark from an A* in chemistry last year in triple science.
I've done my revision and now just doing lots of past papers.
I don't get how all of the hess's law works (enthalpy of reaction, combustion and formation) and how you construct them and what goes at the bottom.
Also has anyone got the june 2012 paper? I can't seem to find it anywhere!
And good luck guys !

Formation reaction

Reactants → Products
↑ ↑
Elements

(One Elements arrow points to Reactants and the other to Products)

Combustion reaction

Reactants → Products
↓ ↓
Combusted products

(Reactant arrow and Product arrow both go to Combusted Products)

Please request examples and more explanation of the Hess' law if this isn't clear.

(edited 11 years ago)

Reply 67

krisshP

14

Original post by lilGem

here you are :smile:

Is the specimen paper worth doing? Some stuff have changed like the diagram they use for mass spectroscopy in the old legacy papers

(edited 11 years ago)

Reply 68

lilGem

20

Original post by krisshP

Is the specimen paper worth doing? Some stuff have changed like the diagram they use for mass spectroscopy in the old legacy papers

I'm yet to do it, but it probably is :cute:

Reply 69

krisshP

14

Original post by lilGem

I'm yet to do it, but it probably is :cute:

After you do it, can you please tell me how good those old papers are and if they are woth doing?

thanks

Reply 70

stealth_writer

4

JuNe 2012 paper anD ms anyone?

Reply 71

lilGem

20

Original post by krisshP

After you do it, can you please tell me how good those old papers are and if they are woth doing?

thanks

will do

Reply 72

krisshP

14

Original post by stealth_writer

JuNe 2012 paper anD ms anyone?

I'm desperate for it as well. But it's too diffiucult to find :frown:

Reply 73

Welbeck

3

Original post by Coombsy

Formation reaction

Reactants → Products
↑ ↑
Elements

(One Elements arrow points to Reactants and the other to Products)

Combustion reaction

Reactants → Products
↓ ↓
Combusted products

(Reactant arrow and Product arrow both go to Combusted Products)

Please request examples and more explanation of the Hess' law if this isn't clear.

Could i have a few more examples, I understand how to work out the energy change but don't get how you fill in the elements or compounds at the bottom single box in the cycle
Thanks

Mark scheme?
Thanks

You saint, thankyou! I did this and got a B a few months back, been looking for a blank script!

Original post by krisshP

Mark scheme?
Thanks

I've got one from my teacher but it needs some scanning up, I'll do it tomorrow if I get time. :smile:

Just to check is it legal posting May papers that aren't available on the site etc?

Reply 76

spleenharvester

18

Oh yeah, also, for people who are having trouble with Hess cycle calculations like I was, it might be worth doing it CGP-sorta style:

1) Identify which is the direct route and which is the indirect route (arrow directions)

2) Remember Route 1 = Route 2

3) Sub in ΔH values in place of Route 1 = Route 2, eg ΔHr = ΔH1 + ΔH2

4) Rearrange algebraically if necessary, i.e equation balancing

5) Sub in the values you're given for calculation if it's required.

Someone correct me if I'm wrong but I haven't gotten a calculation question wrong since looking at that method in the CGP salters book.

Reply 77

krisshP

14

Can anyone give me some tips on the questions which ask you on the pros and cons of fuels like,
Give one advantage and two disadvantages of coal

Reply 78

Zarah01

9

Advantage: easily combustible so little cost and time spent on burning the fuel compared to other fuels
Disadvantage: non renewable resource and its combustion releases harmful pollutants into the air, i.e carbon particulates which affect breathing in people with respiratory problems.

Reply 79

krisshP

14

Original post by Zarah01

Advantage: easily combustible so little cost and time spent on burning the fuel compared to other fuels
Disadvantage: non renewable resource and its combustion releases harmful pollutants into the air, i.e carbon particulates which affect breathing in people with respiratory problems.

But how you know the pros and cons? They are not on the Chemical Ideas book and on the the chemical storyline book there is a lack of detail.

OCR Chemistry B (Salters) Thursday 10th January Discussion

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