ALL CIE CHEMISTRY DOUBTS HERE !!

[Deadly_king]

Exam in three days! Urgent help please!
http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w07_qp_1.pdf
Q: 30 and 21

21. C-Pb bond is a very weak bond...........So tetra methyl lead acts a source of methyl radicals

30. Upon breaking the ester bonds, we can have only two possible acids formed namely CH3CH2CH2CO2H or CH3CO2H.

Hence answer is B

http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_s08_qp_1.pdf
Q:23 and 27

23. Answer is D due to high molecular weight which will prevent the hydrocarbon from rising upon water

27. The formula C10H14O indicates that it should be an alcohol and the fact that it is unreactive to mild oxidising agents, it cannot be a primary one

So you just have to eliminate all the answers which upon hydration would give a primary alcohol This leaves us with B, C and D! But only D gives a tertiary alcohol which we all know is not affected by mild oxidising agents

http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w08_qp_1.pdf
Q: 28

28. The reaction is one forming an ester So to form an ester we usually need and alcohol and a carboxylic acid

If you break the ester bond, you'll get as products CH3CO2H and CH3CH2CH(CG3)CH2OH, this is because the second carbon atom of 2methyl-butyl methanoate contains a double bond with O which indicated that it should be the acidic carbon atom The rests just fits in

Check the answers, if they are good, then my explanation are correct IF not, then am afraid I can't help :/

AM afraid I don't currently have enough time to check the marking schemes or my notes........I just replied according to my knowledge :/

Hope it helps

[NidZ- Hero]

can Someone please Explain me in  details the answerrs of  the Following ?
- Q3
- Q5
- Q8
- Q11
- Q26

http://www.freeexampapers.com/past_papers.php?l=Past_Papers%2FIGCSE%2FChemistry%2FCIE%2F2002+Nov/
paper 1

[Ghost Of Highbury]

can Someone please Explain me in  details the answerrs of  the Following ?
- Q3
- Q5
- Q8
- Q11
- Q26

http://www.freeexampapers.com/past_papers.php?l=Past_Papers%2FIGCSE%2FChemistry%2FCIE%2F2002+Nov/
paper 1

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.

[Twinkle Charms]

Flask X contains 1dm³ of helium at 2kPa pressure and flask Y contains 2dm³ of Neon at 1kPa pressure.
If flasks are connected at constant temperature, what is the final pressure??

[Arthur Bon Zavi]

Flask X contains 1dm³ of helium at 2kPa pressure and flask Y contains 2dm³ of Neon at 1kPa pressure.
If flasks are connected at constant temperature, what is the final pressure??

Total volume = 1dm³ + 2dm³ = 3dm³

PV = nRT

As temperature is constant, PV is constant, so P₁V₁ = P₂V₂

Flask X : (2)(1) = P₂(3)
P₂ = 2/3 kPa

Flask Y : (1)(2) = P₂(3)
P₂ = 2/3 kPa

Total pressure = sum of partial pressures
Total pressure = 2/3 + 2/3 = 4/3 kPa

[perky]

oct/nov 2009 ppr 11 q 28,29,30

[Ghost Of Highbury]

oct/nov 2009 ppr 11 q 28,29,30

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]

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.

Thankkkks Alllot

[Ghost Of Highbury]

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

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.

[NidZ- Hero]

i have couple of doubts It Would be Great if Some one Could Help

http://www.freeexampapers.com/get_past_papers.php?l=Past_Papers%2FA+Level%2FChemistry%2FCIE%2F2002+Nov%2F9701_w02_qp_1.pdf
Questions : 8 ,29, 39


http://www.freeexampapers.com/get_past_papers.php?l=Past_Papers%2FA+Level%2FChemistry%2FCIE%2F2006+Nov%2F9701_w06_qp_1.pdf
Question : 4 , 5 , 6 , 9 , 11 , 14 , 23 , 27 , 37.

http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_s07_qp_1.pdf
Question : 9 ,26


ASAP
Thanku

[Ghost Of Highbury]

This isn't a 'couple of doubts', it's almost half a paper

I have to sleep in a bit, so i'll do w06 questions very quickly. Hope someone can help u with the other 5

4) Construct balanced equations of the combustion. Find out how much volume of O2 hasn't reacted or is in excess. Find out the volume of CO2 given off using mole concept, add 'em up. Do this for all the alkanes.

5) B, sideways overlap. Weak bond. The rest are head to head

6) Ammonia has a lot of different types of bonding between the molecules, hence it deviates the most from the ideal gas. H2 is the closest to an ideal gas, hence straight line. D

9) Use this hess's cycle.

   H2 + CO + 0.5O2 ---(-283)---> CO2 + H2
               \                        /
                \(-286+44)        /
                 \                   /
                  V                V
                   CO + H2O(g)

11)   acid     alchol        ester        water
         1          1             0              0
       1-x       1-x           x                x

(x^2)/(1-x)^2 = 4
Solve for x

14) Calcium nitrate -> calcium oxide + NO2 + O2
Balance, convert to moles, find out the mass of CaO remaining.

23) B - Different groups attached to each Carbon will produce the cis trans.

27) B - Tertiary alchol, so doesn't get oxidized. No reaction. Forms ONa and gives H2 gas.

37) This is a tough one. Can't draw now, but i'll tell u what to do. break the double bonds and put O atoms to each carbon broken from the double bond. See if the 2 products contain a ketone group. One gives an aldehyde group if i'm not wrong. try it

Good luck, I hope you do great tomorrow

Night

[perky]

guyyyyyyyssss any guess for ppr31 practical ?

[whale95]

Are hydrocarbons are all incombustibles? and explain Thanks you

[astarmathsandphysics]

hydrocarbons incombustibles? Tell my car