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ALL CIE CHEMISTRY DOUBTS HERE !!
perky:
oct/nov 2009 ppr 11 q 28,29,30
Ghost Of Highbury:
--- Quote from: perky on May 07, 2012, 09:16:51 am ---oct/nov 2009 ppr 11 q 28,29,30
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27 : 2,4 DNPH reacts with aldehydes and ketones. This molecule has a ketone group, so it will react.
HBr will get added to the C=C
NaBH4 will reduce the C=O group.
Fehling's reagent only reacts with aldehydes, no -CHO group so no reaction.
28 : This one's easy. Start with the general aldehyde molecule R-CHO. The carbon being partially positive, gets attacked by the nucleophile
-CH2CO2CH3. So the final product is R-CH(OH)CH2CO2CH3. Now R can be any alkyl group, the answer is C, where R is the ethyl group (CH3CH2)
29. B. Nucleophilic substitution. CN- ions replace Br. CN gets hydrolysed to COOH. Do these for B and u get the required product.
raamishstudent:
Hey guys just need some1 to clear some doubts of mine.
http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w05_qp_1.pdf
Qs 31 How to do it?
Qs 34) WHy is C not the answer
Qs 20) MY isomers are becoming 4 but the answer is 3.
Qs 5) How to do it?
Please help the exam is tommorrow
NidZ- Hero:
--- Quote from: Ghost Of Highbury on May 05, 2012, 08:48:48 pm ---First I.E + Second I.E is same for Co and Al (757 + 1640 for Co) and (577+1820) = 2397. Use data booklet for IEs
A will have a dipole because Chlorine atoms and Fluorine atoms can be places in different carbons, and due to different electronegativities,
a net dipole remains. Same reason for C and D. The answer, C2Cl4 doesn't have a net dipole because Cl atoms have same Electronegativity and thus
net dipole cancels and is zero.
A 2 g sample of hydrogen at temperature T and of volume V exerts a pressure p. p = nrT/V = 2RT/V (moles of H2 = 2/1 = 2)
check which option gives same pressure. For e.g A gives p = nRT/V = RT/V (n = 2/2 = 1). B gives p = 4RT/V
C gives correct answer because n = 1 + 1 = 2.
2HI <-> H2 + I2
Initially b 0 0
Equilibrium b-x b/2 b/2
(b^2/4)/(1-b)^2
26. First break the double bonds, add the -OH groups and make the diols. NOw, for oxidation to ketone, 2 hydrogen atoms should be lost, one from the -OH group, one from the same carbon atom. And remember u need a diketone, so 2 ketone groups.
It isnt possible to get a diketone in A and D because you'll only get one ketone group in each. From B and C, B gives u an aldehyde after losing th 2 h-atoms, C is the answer.
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Thankkkks Alllot
Ghost Of Highbury:
--- Quote from: raamishstudent on May 08, 2012, 06:07:19 am ---Hey guys just need some1 to clear some doubts of mine.
http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w05_qp_1.pdf
Qs 31 How to do it?
Qs 34) WHy is C not the answer
Qs 20) MY isomers are becoming 4 but the answer is 3.
Qs 5) How to do it?
Please help the exam is tommorrow
--- End quote ---
Q31) The relative molecular mass is the average of all the isotopic mass. So some atoms might have different number of neutrons, hence different nucleon number. The different number of neutrons won't affect the radius. So 1 is correct, 2 is wrong, hence D.
34) 1 is correct, because H+ reacts with OH- ions of the first equilibrium and equilibrium moves to the right. So number of hydroxyapatite molecules decrease. 2 is correct because H+ will react with the PO4(3-) ions and decrease its concentration again moving the equilibrium to the right. 3 is not correct, because Calicium ions won't react with the acid. I'm not sure about the explanation to that, if someone could throw some light on that, it'd be great.
20) 1,1 dichloro ethene. cis 1,2 dichloro ethene and trans 1,2 dichloro ethene. 3 isomers.
5) He and Nitrogen will only have VDW's forces between them, so they can behave like an ideal gas compared to the others. HCl will have VDW's forces stronger than that in CH4 because more number of electrons. It will also have hydrogen bonding, so that's the answer.
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