Chemistry P4 Help needed

[zeebujha]

It is due to increasing Van der Waals' forces.

HOW?????????? Please explain

 

[fluffycloud]

May june 2005 Q2 i don't know how to solve the whole thigngg

 

[bineetojha]

@zeebujha u're AS or A2 ??..if as listen junior..with increasing molecular size down the group the 'size' of electron cloud increases..so more intermolecular forces due to large number of dipole-dipole interactions and hence the color deepens because color depends on the compactness that the molecules are held.//

 

[maniac33]

I see now. Thank you

u'r welcome....

 

[ParanoidAleveler]

http://www.xtremepapers.me/CIE/Internat ... 8_qp_4.pdf


i looked at this question and i was COMPLETELY blank :O:

Question 1) (c) (i) and (ii)

HELPPPP!

 

[zeebujha]

@zeebujha u're AS or A2 ??..if as listen junior..with increasing molecular size down the group the 'size' of electron cloud increases..so more intermolecular forces due to large number of dipole-dipole interactions and hence the color deepens because color depends on the compactness that the molecules are held.//

A2. What doesn't satisfy me about your explanation is: If it was "compactness" as you put it, determining the color, the intensity of the SAME COLOR would deepen. To put it into perspective, Cl2 is yellowish green. So, Br2 would have to darker yellowish green ,not REDDISH BROWN!

 

[bineetojha]

@zeebujha u're AS or A2 ??..if as listen junior..with increasing molecular size down the group the 'size' of electron cloud increases..so more intermolecular forces due to large number of dipole-dipole interactions and hence the color deepens because color depends on the compactness that the molecules are held.//

A2. What doesn't satisfy me about your explanation is: If it was "compactness" as you put it, determining the color, the intensity of the SAME COLOR would deepen. To put it into perspective, Cl2 is yellowish green. So, Br2 would have to darker yellowish green ,not REDDISH BROWN!

you don't seem to get me do you refer to the syllabus section 9.4 ..and check the schemes of work ...and most importantly the syllabus stresses on explanation of the volatility ..not the color and the color are only ought to be described.. got it??

 

[zeebujha]

@zeebujha u're AS or A2 ??..if as listen junior..with increasing molecular size down the group the 'size' of electron cloud increases..so more intermolecular forces due to large number of dipole-dipole interactions and hence the color deepens because color depends on the compactness that the molecules are held.//

A2. What doesn't satisfy me about your explanation is: If it was "compactness" as you put it, determining the color, the intensity of the SAME COLOR would deepen. To put it into perspective, Cl2 is yellowish green. So, Br2 would have to darker yellowish green ,not REDDISH BROWN!

you don't seem to get me do you refer to the syllabus section 9.4 ..and check the schemes of work ...and most importantly the syllabus stresses on explanation of the volatility ..not the color and the color are only ought to be described.. got it??

dude, this is color thing is AS stuff. As A2 "senior" you must know the answer to AS!

 

[bineetojha]

@zeebujha why should i know the answer of something that's not specified in the syllabus ??? ..and why don't u come up with an expalnation of urs..instead of playing jhagada-jhagada with me??

 

[MukeshG93]

@zeebujha u're AS or A2 ??..if as listen junior..with increasing molecular size down the group the 'size' of electron cloud increases..so more intermolecular forces due to large number of dipole-dipole interactions and hence the color deepens because color depends on the compactness that the molecules are held.//

Dude, take a look to the right of Zeebujha's posts and you'll see how much of a senior he is to you. Pft, newbie... And don't you dare going around the forums making people seem inferior to you just because you feel you know more than them, we just post questions because we are not sure, not because we don't know anything about them. And also, in your answer, you have mentioned little to nothing about the intermolecular mechanism of Van der waal's forces. It is due to the larger electron cloud that the probability of an uneven distribution of electrons about the atom increases which causes a chain-induction effect in the chemical sample. One molecule induces an imbalance of charge in another and this continues throughout the sample, creating temporary dipoles. Now, as the number of electrons increases, so does the probability of this uneven shift, which also increases the strength and frequency (don't take it in physical terms, frequency as in the number of times it is likely to happen in a given time) of the VAn der waal's forces. This causes them to bunch up together. Now, you should know that when we take absorption spectrum of a sample species, we take it from a fixed amount of a substance, and when these molecules are tightly packed, they absorb more and the absorption peak becomes higher. A higher absorption peak is reflected as a depth in colour. This is also the reason [Cu(NH3)4]2+ has a deeper color than Cu(OH)2 in aqueous medium. Hope this helps Zeebu. And Bineet, please try not to be a root of trouble, all of us here could do without your attitude. Also, the change in color of the different halogen species is due to the difference in their absorption spectra. Bromine absorbs in the blue region whereas chlorine absorbs more in the red region and somewhat in the blue region. It's due to discrete electron energy levels.

 

[MukeshG93]

@zeebujha why should i know the answer of something that's not specified in the syllabus ??? ..and why don't u come up with an expalnation of urs..instead of playing jhagada-jhagada with me??

How much of a senior are you if you don't bother to look outside the syllabus to make more sense of the things you do know (or mugged up, seeing your attitude towards the A-levels). At least we A2 "juniors" actually BOTHER.

 

[ParanoidAleveler]

http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9701%20-%20Chemistry/9701_w08_qp_4.pdf


i looked at this question and i was COMPLETELY blank :O:

Question 1) (c) (i) and (ii)

HELPPPP!

 

[zeena123]

For the first part of that question you need to take the Mr of 2,3- dibromoprpan-1-ol.
And the second part you just need to take fractions and get the numbers they require. Thats my understanding.

 

[nealDSA]

I've A Doubt, If In The Exam We Are Asked To Draw The Structure Of Compound X .. Is It OK\Allowed If I Draw The Displayed Formula Or Should I Write Like CH3(OH)CH2 ( For e.g ) ??!!

 

[ParanoidAleveler]

For the first part of that question you need to take the Mr of 2,3- dibromoprpan-1-ol.
And the second part you just need to take fractions and get the numbers they require. Thats my understanding.

but for the first part, the ms says ... C3H6OBr2 = 216, 218 and 220
wht does that mean?

 

[MukeshG93]

I've A Doubt, If In The Exam We Are Asked To Draw The Structure Of Compound X .. Is It OK\Allowed If I Draw The Displayed Formula Or Should I Write Like CH3(OH)CH2 ( For e.g ) ??!!

Displayed should be allowed, otherwise it would be a pain to show different groups attached to a benzene ring. Make displayed formulae, they're the best!

 

[zeena123]

For the first part of that question you need to take the Mr of 2,3- dibromoprpan-1-ol.
And the second part you just need to take fractions and get the numbers they require. Thats my understanding.

but for the first part, the ms says ... C3H6OBr2 = 216, 218 and 220
wht does that mean?

Those numbers indicate the molecular mass of each fragment.
So, you should take different fragments of the original molecule and make sure each fragment satisfies the molecular mass, by trial and error.

 

[MagicmanFarhanul]

May juen 2010 paper 43 how do you the E naught values of PBO2 +AH +SO4 +2E---------PBSO4 +2H20

ddude it goes this way,
PBO2+4H+2E+----------PB2+ + 2H20--------ENOT- +1.47
2S2O82- +2E----------2SO42------------------ENOT- +2.01
AND WE KNOW ENOT VALUE =REDUCTION-OXIDATION
=1.47-2.01= -.54
HOPE IT HELPED U OUT.

 

[beacon_of_light]

For the first part of that question you need to take the Mr of 2,3- dibromoprpan-1-ol.
And the second part you just need to take fractions and get the numbers they require. Thats my understanding.

but for the first part, the ms says ... C3H6OBr2 = 216, 218 and 220
wht does that mean?

Since the molecule contains two Br atoms, if you take Br as 79 you'll get 216, if you take Br as 79 and 81.. you'll get 218 and if you take Br as 81 you'll get 220...this is the same as M , M+2 , and M+4 ....

 

[WellWIshER]

GUYS WTH!!!

oct 07 q3 part c 2 and 4

how IS IT POSSIBLE TO OXIDIZE CL AND REDUCE CHROMATE WHEN DA E VALUE OF CL IS GREATER THAN CR+


wt is going on????