Chemistry: Post your doubts here!

[Raiyan3]

15 Use of the Data Booklet is relevant to this question.
The combustion of fossil fuels is a major source of increasing atmospheric carbon dioxide, with a
consequential rise in global warming. Another significant contribution to carbon dioxide levels
comes from the thermal decomposition of limestone, in the manufacture of cement and of lime for
agricultural purposes.
Cement works roast 1000 million tonnes of limestone per year and a further 200 million tonnes is
roasted in kilns to make lime.
What is the total annual mass output of carbon dioxide (in million tonnes) from these two
processes?
A 440 B 527 C 660 D 880

You see the total amount of limestone roasted is 1200 (1000+200)
Now we make the equation
CaCO3 => CaO + CO2
We find the moles of limestone = 1200/(40.1+12+ 16 x 3) = 11.98
Since the mole ratio of CaCO3:C02 is 1:1, we find the mass, we multiply by the mr of co2 which is 44. 11.9 x 44 = 527.47. Ans B

 

[Sohail A. Razzak]

Salamualikum...
Can sumbody answer these question ??
O n 2012 paper 13 question 36,34,26,10

The link fr da ppr is

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_13.pdf

 

[natalee123]

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


Question 4....please explain! Thank you.

Oh and question 11 if you don't mind, thanks!

 

[messi10]

Edit: no longer help needed

 

[LimeReem]

You see the total amount of limestone roasted is 1200 (1000+200)
Now we make the equation
CaCO3 => CaO + CO2
We find the moles of limestone = 1200/(40.1+12+ 16 x 3) = 11.98
Since the mole ratio of CaCO3:C02 is 1:1, we find the mass, we multiply by the mr of co2 which is 44. 11.9 x 44 = 527.47. Ans B

Thank you so so much~!

 

[HubbaBubba]

Can you please tell what papers are these from?

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

 

[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?