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Chemistry: Post your doubts here!

emilyy

emilyy

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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??
 
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Maqb0ol

Maqb0ol

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princess Anu said:
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?
Click to expand...
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
 
S

shoban10

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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?
 
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Emma23

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

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G

Gimmick

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Charlotte20102013 said:
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 :ROFLMAO:
Click to expand...
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.
 
L

Logitech

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Emma23 said:
Hi can someone please help with qn 2 a)
I've the exam tmr,,
Click to expand...
Yeah this was a time consuming question. Anyway so this is what I did. You do the same thing for the diethyl ether, you have to write out the equation and all. Obviously all this working is not required but I cant do any calculations without writing it down.
 

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princess Anu

princess Anu

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The answer to this is B.
Why isn't it A? as the question says ' some covalent character' doesn't this imply least covalent character?Screen Shot 2014-11-21 at 6.46.46 PM.png
 
princess Anu

princess Anu

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Why are we dividing y by 2? although y is the enthalpy change of reaction and it doesn't have to be per mole?jpeg-1.jpeg
 
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