You are Here: Home

# B (Salters) F331 (Chemistry for Life) 22nd May 2015 [Official Thread] watch

1. (Original post by vuvuzela)
Hess Law will blow up this year too.
So will the three hydrocarbon processes

Posted from TSR Mobile
what do you mean by that?)
2. can someone explain the calculations of % on page 42 of the test bank pls
3. (Original post by TheLegalDealer)
Divide the percentage of each atom which is basically its mass in the compound by its atmoic mass to find the moles of it

Do this for all the atoms in the compound .Now find the ratio of the atoms by dividing each of the atoms moles by the moles of the atom that he smallest mole

This would give you a ratio e.g. 21. Then just put the ratio of each atom in the formula e.g. C2H2O
thanku
4. Can anyone explain Question 2d on the june 2014 paper its doing my head in
5. When given bond enthalpies, to work out enthalpy change, do you do products - reactants?
or reactants - products?
6. (Original post by TheLegalDealer)
Can anyone explain Question 2d on the june 2014 paper its doing my head in
same here, still cant get the correct answer after like 10 attempts wtf, helppppppp
7. Sulfur is 10% of 1kg, so mass of sulfur is 100g, and Mr is 32.1
Mol=mass/mr, so you can find moles of sulfur
I assumed moles of sulfur is in the same ratio as mole of SO2 so calculated mole is mole of SO2
Then you can rearrange formula so that mass= moles x Mr of S02, which gives you about 200g
8. (Original post by AAlice97)
Sulfur is 10% of 1kg, so mass of sulfur is 100g, and Mr is 32.1
Mol=mass/mr, so you can find moles of sulfur
I assumed moles of sulfur is in the same ratio as mole of SO2 so calculated mole is mole of SO2
Then you can rearrange formula so that mass= moles x Mr of S02, which gives you about 200g
thank you so much !!!
9. can someone please explain hess law
10. (Original post by dansag)
can someone please explain hess law
If the starting and finishing points are the same the enthalpy change for a chemical reaction will always be the same regardless of the route it takes
11. Isn't it starting and finishing conditions must be the same not points ? how specific is the wording ?
12. (Original post by Obereicher)
Isn't it starting and finishing conditions must be the same not points ? how specific is the wording ?
Not that specific, the previous reply is accurate and would get you all marks

Posted from TSR Mobile
13. (Original post by buckeybarnes)
can someone explain the calculations of % on page 42 of the test bank pls
1.75% of 100g = 1.75g

n=m/Mr

1.75g/9= 0.19 moles (Be)

100g-1.75g= 98.25g

n= m/Mr

98.25/63.25 = 1.55 moles (Cu)

14. (Original post by vuvuzela)
Not that specific, the previous reply is accurate and would get you all marks

Posted from TSR Mobile

It would seem you do unfortunately
15. (Original post by Obereicher)
Isn't it starting and finishing conditions must be the same not points ? how specific is the wording ?
(Original post by vuvuzela)
Not that specific, the previous reply is accurate and would get you all marks

Posted from TSR Mobile
No you have to have conditions, it says not to accept points even though that's what the revision guide says which is strange.
16. ^ i stand corrected. At least i know for tomorrow and hope it comes up

Posted from TSR Mobile
17. (Original post by chococup123)
When given bond enthalpies, to work out enthalpy change, do you do products - reactants?
or reactants - products?
You do reactants- products

If its negative= exothermic
positive= endothermic
18. (Original post by vuvuzela)
Hess Law will blow up this year too.
So will the three hydrocarbon processes

Posted from TSR Mobile
What do u mean by the 3 hydrocarbon processes?

Is it isomerism, cracking and reforming?
19. (Original post by shooting_stars)
What do u mean by the 3 hydrocarbon processes?

Is it isomerism, cracking and reforming?
Yeah. Good luck all

Posted from TSR Mobile
20. Last min prep guys , what most likely to come up ??

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: June 2, 2015
Today on TSR

Will it ever be possible?

### University open days

1. University of Cambridge
Wed, 26 Sep '18
2. Norwich University of the Arts
Fri, 28 Sep '18
3. Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 29 Sep '18
Poll
Useful resources

Can you help? Study Help unanswered threadsStudy help rules and posting guidelines

## Groups associated with this forum:

View associated groups

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