Chemistry: Post your doubts here!

[smartangel]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w09_qp_12.pdf
please explain Q40!!

 

[saudha]

In the past paper you're doing, do you know the answer for 14? The question about the graph of acidity of period 2 oxides. Is the answer A or B? (or something else?)

B

 

[saudha]

A monomer undergoes addition polymerisation. A 1 mol sample of the monomer is completely
polymerised.
How many moles of polymer might, theoretically, be formed?
1.1
2 .10–6
3.6.02 1023(avogadro's constant)

 

[leosco1995]

A monomer undergoes addition polymerisation. A 1 mol sample of the monomer is completely
polymerised.
How many moles of polymer might, theoretically, be formed?
1.1
2 .10–6
3.6.02 1023(avogadro's constant)

If 1 mole of a monomer is polymerized and you obtained the same number of moles of a polymer, then technically... you got the same thing right? So 1 can't be a polymer. 2 and 3 are just random numbers given but they can be polymers because they're not the same # of moles as the monomer.

So C is right.

 

[Casablanca]

B

Thanks.

 

[Oliveme]

Can someone please explain these paper 1 questions?
Thanks.....

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_11.pdf
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_ms_11.pdf
Q8 Why cant the answer be C?
Q16?
Q27 Why is the ratio 3:1?
Q36?

And why isnt the examiner report for this paper available here?

8) because acids give away H+ ions not gain them. look at the backward reaction in equation 2.

27) ultraviolet light means a free radical reaction takes place and this involves HOMOLYTIC fission. Then there are 6 places from where Cl can attack the H to form 1-chloro-propane but only 2 places for attack to form 2-chloro-propane. Thus the 3:1 ratio.

Hope this helps. Good Luck.

 

[hmlahori]

Have some doubts....

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_11.pdf
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_ms_11.pdf
Q16 I'm confused between options B & C. Clarify why its B.
Q36 The non-metallic element has to be nitrogen. It satisfies all the conditions in the question and the statements 1 & 2. But how is nitrogen dioxide polar?

 

[smartangel]

please tell me how to do this question..i dont knw how many times i"ve posted it! but no one has answered it yet
its Q 22 of jun11/11 if you need to refer to the paper. answer is A. PLEASE HELP ME OUT!!

 

[sumaiyarox:)]

y dos the bond length increase btween hydrogen chloride,hydrogen bromide and hydrogen iodide?

 

[hmlahori]

please tell me how to do this question..i dont knw how many times i"ve posted it! but no one has answered it yet
its Q 22 of jun11/11 if you need to refer to the paper. answer is A. PLEASE HELP ME OUT!!

First of all we have to consider the outer electrons of both hydrogen and carbon. Normally CH3 has a total of (4 of carbon+3 of 3 H atoms) 7 outer electrons. For becoming a free radical CH3 does not need to add or remove electrons.(for example the chlorine free radical has the same number of outer electrons 7). So it will have 7 outer electrons. A nucleophile is a donator of a pair of electrons so the C in CH3 needs to gain one electron to have a free non bonding pair of electrons which it can donate(other electrons are already bonded with hydrogen). So it will have 8. An electrophile is an accepter of a pair of electrons so the C in CH3 needs to lose one electron so it can accept a pair of electrons and have a complete outer shell. So it will have 6.
Hope this helps.

 

[smartangel]

First of all we have to consider the outer electrons of both hydrogen and carbon. Normally CH3 has a total of (4 of carbon+3 of 3 H atoms) 7 outer electrons. For becoming a free radical CH3 does not need to add or remove electrons.(for example the chlorine free radical has the same number of outer electrons 7). So it will have 7 outer electrons. A nucleophile is a donator of a pair of electrons so the C in CH3 needs to gain one electron to have a free non bonding pair of electrons which it can donate(other electrons are already bonded with hydrogen). So it will have 8. An electrophile is an accepter of a pair of electrons so the C in CH3 needs to lose one electron so it can accept a pair of electrons and have a complete outer shell. So it will have 6.
Hope this helps.

thank you so much!! yes it did help me out

 

[smartangel]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w07_qp_1.pdf
Q32.. please explain how 2 and 3 are correct!

 

[smartangel]

6 Which of the following least resembles an ideal gas?
A ammonia
B helium
C hydrogen
D trichloromethane
why is the ans A and not D when trichloromethane has a higher mass??

 

[user]

6 Which of the following least resembles an ideal gas?
A ammonia
B helium
C hydrogen
D trichloromethane
why is the ans A and not D when trichloromethane has a higher mass??

aoa wr wb!

Ammonia has hydrogen bonding......!! which is very strong as you know...
and for an ideal gas, one condition is that inter molecular forces are negligible..

 

[Afeef]

6 Which of the following least resembles an ideal gas?
A ammonia
B helium
C hydrogen
D trichloromethane
why is the ans A and not D when trichloromethane has a higher mass??

Gases like ammonia which has strong intermolecular attractions show more deviation ,
In D there exist weak van der wall forces i guess

 

[gestetner]

Help required in Q 1, 2, 40 of May/June 2005 P1
http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s05_qp_1.pdf​

 

[Anoushay]

b

wel yes..u knw hw CIE is!!!

but it can be balanced by option A too.

 

[user]

Help required in Q 1, 2, 40 of May/June 2005 P1​

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s05_qp_1.pdf​

Q: 2

Assalamoalaikum wr wb!
Ok so they said, there's 1 mol of sodium azide..right?

from eqn 1, we know 2 moles produce 3 moles of nitrogen, so one mole will produce 3/2 moles of nitrogen and one mole of sodium...

now from eqn 2, we know 10 moles of sodium produce one mole of nitrogen, we got only one mole of sodium therefore how many nitrogen will be there..=> 1/10

total moles of nitrogen = 3/2 + 1/10 = 1.6

 

[smartangel]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w07_qp_1.pdf
Q32.. please explain how 2 and 3 are correct!

 

[kshumaila52]

Can any one explain why option 3 is wrong ???? Q 38 June 06
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/