Chemistry: Post your doubts here!

[ZaqZainab]

Suchal Riaz can you tell me where from did you read the ionization energy doesn't effect the Melting point?

 

[princessnoor]

one question plz help
in gas phase Al nd a transition element require the same amount of energy to form one mole of an ion with a +2 charge
A: Co
B:Cr
C: Cu
D:Ni
pleasee help!!!
answer is A but how on earth do we come to know tht

 

[Suchal Riaz]

how is the bond energy in graphite stronger than that in diamond?:/

a very interesting question.
in graphene/graphite all CC bonds are not single bonds. they are neither double bonds. it like one p-orbital free electron a double bond for all of the six bonds. in the data booklet you will find "C=C(benzene)" value. it is much higher than C-C.
each bond in graphite is 520kj/mol while in diamond it is 350
3(520)-4(350)=160kj/mol
it means that diamond to graphite is exothermic.
just to be clear i used novice language knowingly. to read about it you can google "bonding in benzene" or read about it in the coursebook in the A2 section.

 

[GCE As and a level]

Guys PLZ help me with this
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_12.pdf
Q10-B
Q16-D
Q20-C
Q23-B
Q25-C
Q28-D
Q37-B

Thnx

 

[Kamihus]

one question plz help
in gas phase Al nd a transition element require the same amount of energy to form one mole of an ion with a +2 charge
A: Co
B:Cr
C: Cu
D:Ni
pleasee help!!!
answer is A but how on earth do we come to know tht

The total of first 2 ionization energies is same.

 

[princessnoor]

a question plz
in an experiment b mol of HI were put into a sealed vessel under pressure p.
ateqilibrium ,x mol of HI had dissociated
2HI--- H2 +I2
now tell how its answer is x2/4(b-x)2
i dont get how the 4 came

 

[Suchal Riaz]

Suchal Riaz can you tell me where from did you read the ionization energy doesn't effect the Melting point?

Jim Clark :

Interestingly, if you compare the ionisation energies with the electrical conductivity of some elements, there is no simple relationship between the two. In Group 1 (usually a well-behaved group as far as trends are concerned) although ionisation energies fall as you go down the group, conductivity falls as well (Li excepted) which is the opposite of what you might expect. There is a table of electrical conductivities on http://periodictable.com/Properties/A/ElectricalConductivity.an.html which you could explore if you could be bothered. In Group 2, the first three conductivities are similar, and then you get the same sort of fall as in Group 1.

author of "chemistry calculation for As and A level" and of ChemGuide.co.uk

 

[princessnoor]

The total of first 2 ionization energies is same.

oh ryt

 

[Kamihus]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s07_qp_1.pdf

Q9, Q29, Explain plz


http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_11.pdf
Q13

Also, how does it hydrochloric acid behave as acid when it is added to NaCl,
And H2SO4 conc. is used for hydrolosis or dehydration, and what about NaOH,

I need urgent help please !!!

s07-Q29
Every aldehyde and ketone undergoes nucleophilic addition with HCN

 

[SIstudy]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q37 (D) why the first statement is correct? I mean the empirical formula has 1 atom of O, so there must be aldehyde :/

 

[Suchal Riaz]

I can't solve any doubts now. i have made many mistakes in solving the doubts which indicate that sleep has overtaken me and i am not able to help you guys without misguiding you.
Have an excellent paper tomorrow
May the odds be in your favour

 

[princessnoor]

guys plzz answer my question
in an experiment b mol of HI were put into a sealed vessel under pressure p.
ateqilibrium ,x mol of HI had dissociated
2HI--- H2 +I2
now tell how its answer is x2/4(b-x)2
i dont get how the 4 came

 

[ZaqZainab]

I can't solve any doubts now. i have made many mistakes in solving the doubts which indicate that sleep has overtaken me and i am not able to help you guys without misguiding you.
Have an excellent paper tomorrow
May the odds be in your favour

Huger game
Best of luck thanks for your time

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q37 (D) why the first statement is correct? I mean the empirical formula has 1 atom of O, so there must be aldehyde :/

it can be aldehyde or ketone. both contain only one C=O

 

[princessnoor]

plz

Huger game
Best of luck thanks for your time

can u answer my question above

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q37 (D) why the first statement is correct? I mean the empirical formula has 1 atom of O, so there must be aldehyde :/

sorry wrong answer.
correct answer is that as the molecular formula shows that there are 4 carbon and 10 hydrogen, it must be an alcohol as any C=O will decrease the number of hydrogen by 2. it has general formula CnH2n-2O. ketones/aldehydes have formula CnH2nO

 

[Kamihus]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q37 (D) why the first statement is correct? I mean the empirical formula has 1 atom of O, so there must be aldehyde :/

it can be aldehyde or ketone. both contain only one C=O

Wrong. Cannot be aldehyde as molecular formula contains 10 H but butanal would contain 8 H.

 

[MiniSacBall]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_11.pdf

Q13, i don't how to get this, i have got volume as 60 cm3, how is it 30 cm3

 

[ZaqZainab]

plz

can u answer my question above

Can you tell the paper?

 

[Suchal Riaz]

guys plzz answer my question
in an experiment b mol of HI were put into a sealed vessel under pressure p.
ateqilibrium ,x mol of HI had dissociated
2HI--- H2 +I2
now tell how its answer is
i dont get how the 4 came

i don't understand your question. what is for and what is x2/4(b-x)2