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ALL CIE CHEMISTRY DOUBTS HERE !!
elemis:
--- Quote from: Martin Luther King Jr on December 08, 2010, 12:25:09 pm ---Jun 03 p1 No 33
It is given that the conversion of graphite to diamond is endothermic.
1. The enthalpy change of atomisation of diamond is smaller than that of graphite -----> It is correct since converting graphite to diamond is endothermic meaning graphite requires more energy.
2. The bond energy of the C-C bonds in graphite is greater than that in diamond -----> It is correct as well since in diamond, each carbon carries 4 bonds while in graphite they carry only 3 bonds.
3. The enthalpy change of combustion of diamond is greater than that of graphite -----> It is correct too dor the same reason as the first one.
So answer is A.
--- End quote ---
You are contradicting yourself. If Carbon has 4 bonds and its atoms are arranged tetrahedrally then it should have a LARGER BOND ENERGY than graphite.
Therefore, wouldnt this eliminate option 2 ?
Can you explain how option 1 is correct in more detail ?
Deadly_king:
--- Quote from: Kirin on December 09, 2010, 04:51:45 am ---You are contradicting yourself. If Carbon has 4 bonds and its atoms are arranged tetrahedrally then it should have a LARGER BOND ENERGY than graphite.
Therefore, wouldnt this eliminate option 2 ?
Can you explain how option 1 is correct in more detail ?
--- End quote ---
Nope........am not contradicting myself dude. Let me get it clear for you.
Bond energy is not the 4 C-C bonds present but only one of them. A carbon atom in carbon carries 4 bonds, so the force of attraction needs to be divided exactly in 4. While in graphite the force of attraction is divided in only 3.
So the bond energy in graphite will be larger. ;)
Option 1.
Enthalpy change of Atomisation can also be considered as the energy required for breaking of bonds to form C(g). So since bond energy for graphite is larger, so will be atomisation energy.
elemis:
Okay, I see.
--- Quote ---It is correct since converting graphite to diamond is endothermic meaning graphite requires more energy.
--- End quote ---
So what if its endothermic ? How did you realise graphite requires more energy ?
Deadly_king:
--- Quote from: Kirin on December 09, 2010, 05:26:37 am ---Okay, I see.
So what if its endothermic ? How did you realise graphite requires more energy ?
--- End quote ---
Hmm.........I had the same explanation I gave you, in mind.
elemis:
http://www.xtremepapers.net/CIE/International%20A%20And%20AS%20Level/9701%20-%20Chemistry/9701_w04_qp_1.pdf
Question 13. I understand the answer is D and that you need a strong acid and base, but why ? What is the chemistry behind all of this ?
Why wouldnt a strong acid and weak base give a SHARP colour change ?
What chapter does this appear in the chem book by Brian Ratcliff ?
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