Edexcel IAL, Unit 5: Transition Metals and Organic Nitrogen Chemistry. 22-Jun-2016

hey where is everybody from? :smile:

Reply 41

imnoteinstein

Hey could some explain these questions please:

https://doc-00-5g-docs.googleusercontent.com/docs/securesc/ha0ro937gcuc7l7deffksulhg5h7mbp1/q9knucmjq9kpvf1tangropdq2h7egb05/1460707200000/01042298237316186224/*/0B1ZiqBksUHNYVzR2LVBMZWI0UnM
Q15 - how do you know the answer's A?

Q8 - The way I got 90degrees by saying that each N forms one bond, so each molecule forms 2, so 3 molecules form 6 bonds which is why its octahedral but that hardly makes sense? So what's the logical way of arriving at 90?

Reply 42

Mehodax

Original post by imnoteinstein

Hey could some explain these questions please:

https://doc-00-5g-docs.googleusercontent.com/docs/securesc/ha0ro937gcuc7l7deffksulhg5h7mbp1/q9knucmjq9kpvf1tangropdq2h7egb05/1460707200000/01042298237316186224/*/0B1ZiqBksUHNYVzR2LVBMZWI0UnM
Q15 - how do you know the answer's A?

Q8 - The way I got 90degrees by saying that each N forms one bond, so each molecule forms 2, so 3 molecules form 6 bonds which is why its octahedral but that hardly makes sense? So what's the logical way of arriving at 90?

I can't open the link you posted
Tell me which paper is it?

Reply 43

Mehodax

Original post by Tomasio

What are people finding to be the hardest topic in chem5?
IMO T metals are just horrible, so damn fiddly and so much stuff to learn....
Am finding other topics such as REDOX pretty easy though tbh

The organic stuff as a whole can be tricky as there's a lot to remember

Reply 44

imnoteinstein

Whoops, sorry
Its the June 2015 paper (not ial/not R)

http://www.physicsandmathstutor.com/past-papers/a-level-chemistry/edexcel-unit-5/

Original post by Mehodax

I can't open the link you posted
Tell me which paper is it?

Reply 45

bobbydylan

3

Having a high ^s system means that there are more product particles than reactants and therefore the eq. constant is greater...

Reply 46

imnoteinstein

Original post by bobbydylan

Having a high ^s system means that there are more product particles than reactants and therefore the eq. constant is greater...

riiight so the first equation has '5 more products' and second one has '2 more products' than their reactants and since first one has more, the K value is greater. Right?

Thankyou! :smile:

Reply 47

They do have topicwise past paper questions and answers for chem at physicsandmathstutor.com aswell.

Reply 48

All rounder

hey could anybody tell why the answer is A???
Q.It is calculated that, as a result of delocalization, benzene has a stabilization energy of 150 kJ mol−1. This means that:
A- the enthalpy change for the conversion of benzene to cyclohexa-1,3,5-triene
would be +150 kJ mol−1.
B -the enthalpy change for the conversion of cyclohexa-1,3,5-triene to benzene
would be +150 kJ mol−1.
C - the enthalpy change for the conversion of cyclohexane to benzene is
+150 kJ mol−1.
D -the enthalpy change for the conversion of benzene to cyclohexane is
+150 kJ mol

Reply 49

Original post by All rounder

hey could anybody tell why the answer is A???
Q.It is calculated that, as a result of delocalization, benzene has a stabilization energy of 150 kJ mol−1. This means that:
A- the enthalpy change for the conversion of benzene to cyclohexa-1,3,5-triene
would be +150 kJ mol−1.
B -the enthalpy change for the conversion of cyclohexa-1,3,5-triene to benzene
would be +150 kJ mol−1.
C - the enthalpy change for the conversion of cyclohexane to benzene is
+150 kJ mol−1.
D -the enthalpy change for the conversion of benzene to cyclohexane is
+150 kJ mol

I guess i'd need to check with my teacher xD

Reply 50

All rounder

yess plx the answer is A idk why! :smile:

Reply 51

Original post by All rounder

yess plx the answer is A idk why! :smile:

It's given on student's book pg.195 and hodder's pg.182.
Basically due to Delta Hydration values of benzene and 1,2,3 blah blah x)

As when you hydrogenate cyclohexene about 119.5 kJ/mol energy is released ,say 120 kJ/mol (so Delta Hydration is -119.5 kJ/mol)
Now if you hydrogenate theoretical 1,2,3 cyclohexatriene you release (3x119.5=358.5 kJ/mol that's about 360 kJ/mol according to book)
But hydrogenation of benzene releases only 207.5 or 208 kJ/mol. thats (Delta Hydration -208 kJ/mol)

so the difference between benzene and 1,2,3 cyclohexatriene is 150kJ/mol.
If you convert 1,2,3cyclohexatriene to benzene Delta Hydration is -150 kJ/mol as benzene is at a lower energy level (so energy is released)
whereas if you convert benzene to 1,2,3 cyclohexatriene you need 150 kJ/mol energy (Delta Hydration is +150 kJ/mol)
That's all I understood. hope this helps! :smile:

(edited 8 years ago)

Reply 52

Original post by All rounder

hey could anybody tell why the answer is A???
Q.It is calculated that, as a result of delocalization, benzene has a stabilization energy of 150 kJ mol−1. This means that:
A- the enthalpy change for the conversion of benzene to cyclohexa-1,3,5-triene
would be +150 kJ mol−1.
B -the enthalpy change for the conversion of cyclohexa-1,3,5-triene to benzene
would be +150 kJ mol−1.
C - the enthalpy change for the conversion of cyclohexane to benzene is
+150 kJ mol−1.
D -the enthalpy change for the conversion of benzene to cyclohexane is
+150 kJ mol

Here's how i summed it up, although its kinda ugly and hard to understand! :colondollar:

well, let me know if you still don't understand! x)

Reply 53

All rounder

omg I FINALLY get this !! thnxx ALOT for ur help :smile:

Reply 54

Original post by All rounder

omg I FINALLY get this !! thnxx ALOT for ur help :smile:

I'm happy It was useful! x)

Reply 55

jwanjwan

is anybody here taking this unit in indian, or around asia. I would be grateful if somebody would discuss the exam with me after so i can get a rough idea of where i have gone wrong

Reply 56

Original post by jwanjwan

is anybody here taking this unit in indian, or around asia. I would be grateful if somebody would discuss the exam with me after so i can get a rough idea of where i have gone wrong

yea i study in muscat. sure i will x)

Reply 57

Tomasio