Edexcel IAL Chemistry Unit 01 - 26th of May, 2017

Original post by mr.holmes

thank you so much
could you please help me with this question:
Which equation represents the reaction for which the enthalpy change, H, is the mean bond energy of the C-F bond?
A CF4 (g) ------- C(g) + 4F(g)
B ¼CF4 (g) --------¼C(g) + F(g)
C C(g) + 4F(g) --------- CF4 (g)
D ¼C(g) + F(g) -----------¼CF4 (g)

i think its B..as everything has to be 1:1 ratio.. but i m not very sure.. sorry...
can u tell me which year this paper is?
whats the mark scheme answer?

Reply 82

neelc21

8

Original post by mr.holmes

thank you so much
could you please help me with this question:
Which equation represents the reaction for which the enthalpy change, H, is the mean bond energy of the C-F bond?
A CF4 (g) ------- C(g) + 4F(g)
B ¼CF4 (g) --------¼C(g) + F(g)
C C(g) + 4F(g) --------- CF4 (g)
D ¼C(g) + F(g) -----------¼CF4 (g)

Is it A

Reply 83

Original post by neelc21

Is it A

but then its not the same mole ratio right?
how is it so? can u please explain... :/

Reply 84

mr.holmes

5

Original post by zooshan

i think its B..as everything has to be 1:1 ratio.. but i m not very sure.. sorry...
can u tell me which year this paper is?
whats the mark scheme answer?

it is May 2013
question 17
and the answer is B
but if it is 1:1 why is it 1/4 of the carbon?

Reply 85

Original post by mr.holmes

it is May 2013
question 17
and the answer is B
but if it is 1:1 why is it 1/4 of the carbon?

there are 4 fluorine..
it does say that the bond enthalpy is a mean of all the bonds..

Reply 86

mr.holmes

5

Original post by zooshan

there are 4 fluorine..
it does say that the bond enthalpy is a mean of all the bonds..

if you can explain more?

Reply 87

neelc21

8

Original post by zooshan

but then its not the same mole ratio right?
how is it so? can u please explain... :/

I dont know, i just guessed

Reply 88

Original post by mr.holmes

if you can explain more?

makes sense?

Original post by neelc21

I dont know, i just guessed

oh.. okay..

Reply 90

waow

Anyone got some last minute short revision notes, would be really helpful.

Reply 91

https://chemrevise.org/3-edexcel-revision-guides/

Original post by waow

Anyone got some last minute short revision notes, would be really helpful.

Reply 92

OP

BEST OF LUCK FOR YOUR EXAM TODAY, EVERYONE!!! :rave:

I couldn't tag u guys, so I'm quoting you:

1.

Original post by Aadha24

x

2.

Original post by waow

x

I'm extremely sorry if I had missed out anyone :colondollar:

(edited 6 years ago)

Reply 93

OP

Original post by raai ahamed

ok fine sis!!!!

Don't be angry with me bro
You haven't edited it yet
But it's ok
I don't think anyone would notice

Reply 94

CaptainJackFail

9

Original post by mr.holmes

thank you so much
could you please help me with this question:
Which equation represents the reaction for which the enthalpy change, H, is the mean bond energy of the C-F bond?
A CF4 (g) ------- C(g) + 4F(g)
B ¼CF4 (g) --------¼C(g) + F(g)
C C(g) + 4F(g) --------- CF4 (g)
D ¼C(g) + F(g) -----------¼CF4 (g)

If they had asked an equation to represent 4deltaH, it'd be A
However they asked an equation to represent deltaH.
Answer is B
Carbon has already gone under atomization, so its mole ratio really don't matter.
If you look at the enthalpy change of atomization of fluorine,
1/4F4(g) --------> F(g) deltaH
F4(g) ------------> 4F (g) 4delta H (x4 all)

Definition of (standard) enthalpy change of atomization
The standard atomisation enthalpy is the enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard state (under standard conditions).
Can't be C or D as bond energy involves the breaking of bonds, which is an endothermic process.

Reply 95

CaptainJackFail

9

Exam starts in 1 and a half hour for me.. best of luck to everyone!!! :biggrin:

Reply 96

cenet0:o

11

Guys how was the paper.. Just finished mine

Reply 97

OP

Original post by mandax_25

Guys how was the paper.. Just finished mine

How was yours?
Was the paper just like how you expected?

Reply 98

OP

Original post by CaptainJackFail

Exam starts in 1 and a half hour for me.. best of luck to everyone!!! :biggrin:

Are you from the UK?
I guess sri lankans might have finished their exam coz it's started at 10 AM I guess

Original post by Aadha24

x

Have you finished ur exam? How was it? Easy?

Reply 99

OP