Thanks mortaz;
Anybody seen this question before?

Calculate the temperature at which Stot is zero?
Whats the best way to remember this calculation, i just learnt that it's DeltaH / Ssys why is it this though? i dont understand

Yeh It has come up quite a few times

u have to rearrange the equation to make T the subject and then go on from there.
Im going to stop there and let somone else take over because Im beginning to confuse myself :rolleyes:

trying to explain in words/steps.

Reply 584

agoodwin

could anyone explain how to do this question please?

its question 5 part d
http://pdf.ocr.org.uk/download/pp_11_jun/ocr_66612_pp_11_jun_gce_uf335.pdf?

thanks :smile:

Reply 585

swimming002

have people revised how to attach dyes to fibres? revision guide not very helpful and specification doesn't really elaborate so do we actually need to know about mordanting agents (trichlorotriazine - or whatever its called?!) etc...

Reply 586

Bi0logical

7

Explain how Kekule's structure accounts for some but not all evidence from the electron diffraction data:
Answer:
accounts for: bond angle same / 120 
three bonds OR three groups / sets of electrons around each carbon 
does not account for: bond lengths equal 
single bonds longer than double bonds 

Reply 587

Hazel247

Original post by Bi0logical

Got a tricky question here;
Calculate the mass of CO2 that would be formed when burning 1.00g of Benzene?

You would work out the moles of benzene:

mole = mass/Mr
Mr = (12x6) + 6
= 78
mole = 1/78
= 0.013mol

For every mole of benzene, six moles of CO2 would be formed so:

0.013 x 6 = 0.078

and, mass = mole x Mr
Mr = 12 +32
= 48
mass = 48 x 0.078
= 3.7grams

Reply 588

mortaz786

Original post by Bi0logical

Got a tricky question here;
Calculate the mass of CO2 that would be formed when burning 1.00g of Benzene?

write an equation:

2cH+2.502 ---->2co2+h2o

1g of ch... mr of ch is 13.. mass/mr =1/13 = moles of benzene.

same ratio of benzene and c02 so moles x mr is mass. 1/13 x 44 =3.38 g :smile:

Reply 589

master_blaster66

17

Original post by swimming002

have people revised how to attach dyes to fibres? revision guide not very helpful and specification doesn't really elaborate so do we actually need to know about mordanting agents (trichlorotriazine - or whatever its called?!) etc...

im not revising for that...doesnt sound familiar to our course

Reply 590

master_blaster66

17

can someone help me with nmr via skype please

(edited 11 years ago)

Reply 591

Princess Kawaii

OP

15

when converting from KJ to J u multiply by a 1000 right ?

Reply 592

Hazel247

Original post by Princess Kawaii

when converting from KJ to J u multiply by a 1000 right ?

Yes... If you think of the 'K' as being interchangable with 'x10^3' I find it helps :smile:

Reply 593

Princess Kawaii

OP

15

Original post by swimming002

have people revised how to attach dyes to fibres? revision guide not very helpful and specification doesn't really elaborate so do we actually need to know about mordanting agents (trichlorotriazine - or whatever its called?!) etc...

What are those ^ ?

Reply 594

Rainbow_2010

2

Original post by Princess Kawaii

when converting from KJ to J u multiply by a 1000 right ?

yep

Reply 595

mortaz786

Original post by swimming002

have people revised how to attach dyes to fibres? revision guide not very helpful and specification doesn't really elaborate so do we actually need to know about mordanting agents (trichlorotriazine - or whatever its called?!) etc...

WTF????

Reply 596

Hazel247

Does anyone understand what an Ionic liquid is? And why it's used in the Friedel Crafts reactions?

Reply 597

Princess Kawaii

OP

15

Original post by Bi0logical

Explain how Kekule's structure accounts for some but not all evidence from the electron diffraction data:
Answer:
accounts for: bond angle same / 120 
three bonds OR three groups / sets of electrons around each carbon 
does not account for: bond lengths equal 
single bonds longer than double bonds 

I don't understand the last point. Can u/anyone explain it?

I thought that in the new model the bonds are of equal length which is the length inbetween the length of single bonds and double bonds