Chemistry: Post your doubts here!

[Charlotte20102013]

CH4 + Cl2 = CH3Cl + HCl
Cl2 reduced to form Cl(-).
C(4-) in CH4 oxidized to C(2-) in CH3Cl.
Hope this helped.

Ahhh... Now I get it.. Thank you!

 

[princess Anu]

It's easy, just follow the instructions, it says from U to R which means the direction would change (arrow) and positive enthalpy would be reversed by sign. whereas 2nd option is wrong because endothermic is donated by +ve sign

Can u explain clearly why 2nd is wrong? I did the calculation for it like if we're going from T to S we can use T-U and U-S so (-75+92=+17) the answer is + so can be endo, no?

 

[princess Anu]

the answer is A . somebody plz explain why others are wrong?

 

[savera]

could anyone explain Q3(c)(i)(ii)?

 

[princess Anu]

why are we dividing y by 2??

 

[100]

somebody please if you have the chemistry standards booklet please upload it! NEED IT ASAP!!

 

[maryam fatima]

plz tell me what to do with the construction lines in paper ? :/

 

[maryam fatima]

plz tell me what to do with the construction lines in paper ? :/

in paper 5 of chemistry?

 

[emilyy]

Two moles of compound P were placed in a vessel. The vessel was heated and compound P
was partly decomposed to produce Q and R. A dynamic equilibrium between chemicals P, Q and
R was established.
At equilibrium x moles of R were present and the total number of moles present was (2 + 2/x ).What is the equation for this equilibrium reaction?
A P(r.a)P 2Q + R
B 2P(r.a)2P 2Q + R
C 2P(r.a) 2PQ + R
D 2P(r.a) 2PQ + 2R
CAN sombdy explain and give me the answer??

 

[janasalem]

Can someone explain this to me ?

 

[PlutoHuman]

How do find the answer to this!

 

[PlutoHuman]

View attachment 49036
Can someone explain this to me ?

Is it A?

 

[janasalem]

no it's D

 

[Maqb0ol]

Can u explain clearly why 2nd is wrong? I did the calculation for it like if we're going from T to S we can use T-U and U-S so (-75+92=+17) the answer is + so can be endo, no?

From T-U it is (-75 kJ/mol) and as from U-S the the direction of arrow will be changed so the value would be (-92 KJ/mol) so total value has -ve sign with it this shows it is exothermic

 

[janasalem]

Can anyone help ?

 

[Charlotte20102013]

Can someone please explain
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_12.pdf
Q26 (Ans: D)
Thank you

 

[shoban10]

Hello! I got 69 for AS chem. But I really messed up p4 in A2 and I think I'll only get ard 10-15 out of 100 for p4... Is it still possible to get a D?

 

[Camille96]

http://www.gceguide.com/2014/08/download-as-level-chemistry-9701-may.html?m=1

Hey guys, help me out with june 14 paper51 no. 1 (b) (i), pleeeaase!
Please, send me the diagram of the apparatus, please, it's urgent. I have p5 exam tomorrow

 

[Emma23]

Hi can someone please help with qn 2 a)
I've the exam tmr,,

 

[Gimmick]

Can someone please explain
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_12.pdf
Q26 (Ans: D)
Thank you

D is a tertiary halogenoalkane, they undergo Sn1 nucleophilic substitution (the Br breaks off and then, very quickly, OH- replaces it) and so the rate determining step is the Br bond breaking (and thus dependent on the concentration of the organic molecule only); since the substitution of OH- is very fast compared to it, adding more OH- does not increase the rate.