Chemistry: Post your doubts here!

[strangerss]

It is.

the why in OCT/NOV 2012 13 THE FIRST answer is D which is not a straight line but a curve?

 

[Raiyan3]

Please help in question number 4
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_12.pdf

 

[Malik777]

what about question 34 in may june 07? Thanks

hey plz Q 9 in the same papers May 2007 :/

 

[HubbaBubba]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s07_qp_1.pdf Q9 plz :/

With credit to h4rriet who helped me with this earlier

You're taking the Kc for the reverse reaction, so you'll take the reciprocal of the forward reaction. Then, look at reaction II, and you'll see that all the moles have been divided by 2. Therefore you take the square root of the reciprocal of the Kc.

 

[strangerss]

For 11, n has to be the number of bonds in the compound. For example, the bond energy of a C-H bond is found by divided the enthalpy of formation of CH4 by 4, because there are 4 C-H bonds in CH4.

WHAT about D? if the compound was NH3 for example so the n number is 3 so you divided the bond energy by 3 and the answer will be correct right?

 

[Raiyan3]

The last one is from 2003 november.
The rest are from 2011 paper 12

Hubbabubba looks like you have done w11 paper12. How did you do question number 4? :/

 

[strangerss]

alsalum allaykom
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_13.pdf question 34 and 36 please :/

 

[Raiyan3]

okay its eating my head. How do we do this? question number 4
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_12.pdf

 

[Saad (سعد)]

When you write the equation for the decomposition of a Group II metal nitrate, you see that the mole ratio of the metal nitrate to the metal oxide is 1:1. So n(nitrate)=n(oxide). You have the mass of the nitrate and you can find the mass of the oxide (mass of nitrate minus mass of gases). You can calculate the molecular mass of Group II metal nitrate and oxide knowing the general formulae: M(NO3)2 and MO. M can be x. Cross multiply.

Jazak Allah Khayr again.

Question 7 and 30: http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_12.pdf

 

[natalee123]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf


Question 4 and question 11

Please help....exam tomorrow!! Thank you

 

[Student12]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf Q7 (A), 8(D), 11(C), 22(C), 28(B), 39(A)
HELPPPPPPPPPPPPPPPP !

 

[Aries_95]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf


Question 4 and question 11

Please help....exam tomorrow!! Thank you

Q.4:

use the equation:
CnH2n+2 +(3n+1)O2----> nCO2+ (n+1)H20.
where n=1,2,3,4
the graph should be a straight line with a negative gradient.​

 

[white rose]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
anyone plzz explain q. 7 & 14

 

[white rose]

Somebody please reply fast.. i have 2 hours left. Im done with all the papers back till 2002. Ive gone through my notes once. what should i do right now?? chemguide or the book (coursebook by David Acaster) plz note that I have 2 hours only and went through each looong way back

which variant r u giving?

 

[messi10]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_11.pdf

MCQ number 21 and 26 please!

 

[Alicee]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_12.pdf
16,20 and 28...please help!!

 

[imperial]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_12.pdf
16,20 and 28...please help!!

16 is D, ClO-3 (V) is formed

20: products of the NaOH(aq) hydrolysis is Sodium Ethanoate and Propanol

Mr of NaCH3COOH/Total Mr of the products * 100: 57.7

so it's C

 

[HubbaBubba]

Hubbabubba looks like you have done w11 paper12. How did you do question number 4? :/

Sorry for the late reply, I had to revise a topic in chemistry. BTW I did Summer 2011 not Winter but I'll help you

q4 - It says there's 96kg of Hydrogen leftover, so 120-96 = 24kg of H2 was used in the reaction.

no. of moles of H2 = 24kg/2 = 12 moles.
N2 + 3H2 ---> 2NH3.

Ratio of Hydrogen to Ammonia is 3: 2
that means number of moles of ammonia produced is 8 moles.
Then you calculate the mass of ammonia which is moles * Molar Mass (8 * 17) = 136kg. Answer is C

 

[Alicee]

16 is D, ClO-3 (V) is formed

20: products of the NaOH(aq) hydrolysis is Sodium Ethanoate and Propanol

Mr of NaCH3COOH/Total Mr of the products * 100: 57.7

so it's C

okay!! thanks!

 

[HubbaBubba]

21 An alkene has the formula CH3CH=CRCH2CH3 and does not possess cis-trans isomers. What is R?
A) H
B) Cl
C) CH3
D) C2H5

Why can't it be B? Why is the answer D?