Chemistry: Post your doubts here!

[strangerss]

O

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_33.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_ms_33.pdf
I guess you're talking about 1 c part iii, you have to multiply the answer you got in part ii with 10 because if 25 cm3 of Fa1 have the amount of moles you found out for ii, then 250 cm3 of FA1 has 10 times as much amount of moles..
see, i think you're confused because you probably think that the II mark on the mark scheme is for part ii. But it's not. It is one whole mark consisting of what calculation you did in part ii and iii.
Then for iv you multiply the Mr of FA1 with the moles from iii and then divide it by the mass of FA1 you found in 1a. 'weighing out the salt' part and times it with 100.

Okay I got it , thanks a lot for the help , jazak alallah 5ayran.

 

[strangerss]

Can some one please tell me how they to solve question 1c in Maj/June 2008 31 varaint?

 

[strangerss]

Is the unit for 1000/reaction time in seconds , s^-1 or 1000s^-1 ?

 

[Rahma Abdelrahman]

darknessinme Thanks
Really appreciated

 

[Es Jay]

how do you calculate the uncertainty in the measurement of time using a stopwatch?

 

[strangerss]

how do you calculate the uncertainty in the measurement of time using a stopwatch?

the smallest reading in a stop watch would be 1 second so , 1/2 = 0.5 seconds , any one do please correct me if I'm wrong

 

[Sughontha]

if I altered my thermometer reading after i wrote it down in the table with pen,will I get a U?

 

[Es Jay]

the smallest reading in a stop watch would be 1 second so , 1/2 = 0.5 seconds , any one do please correct me if I'm wrong

the smallest reading is 1 millisecond, of this i'm sure. But i was thinking, don't we consider the reaction time when we write time uncertainties?

 

[syed1995]

FINALLY DONE WITH IT.. MCQs here we come

 

[strangerss]

the smallest reading is 1 millisecond, of this i'm sure. But i was thinking, don't we consider the reaction time when we write time uncertainties?

No we don't , but if they tell you to write the minimum reaction time then you subtract the uncertainty fro the reaction time and vice versa for the maximum reaction time , hope you got it

 

[Es Jay]

No we don't , but if they tell you to write the minimum reaction time then you subtract the uncertainty fro the reaction time and vice versa for the maximum reaction time , hope you got it

Yes, I did...thank you so much

 

[Rahma Abdelrahman]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Please help with the following questions:
Q12
Q26, why 6 isomers, why not 5?
Q29 (If u can explain it here , if not no problemo )
Q30, Why answer is A and not B?
Q35.... In the first sentence, how does N undergo REDOX rx. ?? I guess it is only oxidised as oxidation state increases from -3 to zero
Thanks in advance..

 

[hela]

Please help with the following questions:
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q23 Q36
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q13 Q22
Thanks in advance..

 

[hela]

Please help with the following questions:
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q23 Q36
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q13 Q22
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_13.pdf Q10

 

[hela]

Please help with the following questions:
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q23 Q36
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q13 Q22
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_13.pdf Q10

Please help with the following questions:
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q23 Q36
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q13 Q22
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_13.pdf Q10
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_12.pdf Q 20

 

[hela]

Please help with the following questions:
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q23 Q36
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q13 Q22
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_13.pdf Q10

Please help with the following questions:
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q23 Q36
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q13 Q22
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_13.pdf Q10
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_12.pdf Q 20​

 

[daredevil]

Please help with the following questions:​

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf ​

Q23 Q36​

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf ​

Q13 Q22​

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_13.pdf Q10​

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_12.pdf Q 20​

i just got around to Q 36.
look if it is Nitrogen or Sulphur then all three options ought to be correct.
because they have told us that it is polutant gas so we know it will be an oxide of N or S.
if one more O is added to the molecule (the molecule is oxidised) then the oxidation number definitely increases by to :-
NO + O --> NO2 ox no. of N increases from 2+ to 4+
SO2 + O --> SO3 ox no. of S increases from 4+ to 6+

no matter if it is N or it's S .... the molecule will definitely have an unpaired electron in both the cases because not all valence electrons bind in S or in N.

as Y is a molecule of N/S and O so two different elements means it is polar. due to the electronegativity difference.

 

[Rahma Abdelrahman]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Please help with the following questions:
Q12
Q26, why 6 isomers, why not 5?
Q29 (If u can explain it here , if not no problemo )
Q30, Why answer is A and not B?
Q35.... In the first sentence, how does N undergo REDOX rx. ?? I guess it is only oxidised as oxidation state increases from -3 to zero
Thanks in advance..

 

[Rahma Abdelrahman]

Please help with the following questions:
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q23 Q36
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q13 Q22
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_13.pdf Q10
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_12.pdf Q 20

Q23--> I did this question just yesterday... They said the mole fraction of ethene is 0.5 meaning ethene is half of the products.. So if there are 8 C atoms, 4 must be from ethene and 4 are from methane and propene ..
If there are 6 C, then 3 must be ethene, then only 3 will remain from the six.. which is not possible as methane and propene together have 4 C atoms.. try like this for the others as well.. Answer is B
Q36 Explained
Q13--> Sorry no idea A small guess may be that as CO2 is produced twice, there shd be 2 compounds with carbonate.. so it's C or D But I don't know why it is C not D..
Q22--> I also have a problem with this question.. there was a similar one somewhere but i couldn't solve either.. I think you got an answer that is not in the choices.
Q10--> enthalpy change of neu. is same because NaOH and Ba(OH)2 are both strong alkalis while HCL and H2SO4 are both strong acids..
Similar to June 2012 P11 Q13 above (That I have no idea about )

 

[ahmed abdulla]

for question 8 u need to do a hess cycle diagram which will look like this....

the values of 590 and 1150 are the first and second ionisation energies!

for question 28 the answer is B because if u can see when we write skeletal formulas we dont include the hydrogen attached on the carbon. the only one that has that is B!

bro .. i posted the WRONG year !
its 2004 .. sorry for that ... http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s04_qp_1.pdf
q8 .... i kept thinking from wr the calcium any way can u help me out with this