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ALL CIE CHEMISTRY DOUBTS HERE !!
Master_Key:
Nov 08
Q3 - Ans:- D
One electron in S orbital means that it is in S-block of periodic table but the first group.
elemis:
Nov. 09 Variant 1
Question 5
A and D are eliminated as they are symmetrical and hence have no overall dipole moments.
In C Chlorine is very electronegative and hence tugs hard at the electrons. Oxygen which is even more electronegative tugs even harder so the net dipole moment is very small.
In B we see that hydrogen can offer little resistance to the effect of the highly electronegative oxygen causing a large dipole moment in the direction of oxygen
Ans = b
Deadly_king:
--- Quote from: moon on November 15, 2010, 01:16:31 pm ---pls can u help in Nov.08 Q3,30,39
--- End quote ---
Nov 08 p1
30. First you need to use the mass of the respective molecules given to find the number of moles of each.
No of moles = Mass / Mr
No of moles of ethanol : 30/46 = 0.652
No of moles of ethanoic acid : 30/60 = 0.50
Ratio of moles of ethanol to ethanoic acid was supposed to be 1:1. Hence we can deduce that ethanol is in excess. Only 0.5 mole of each reactant will react.
No of moles of ethyl ethanoate : 22/88 = 0.25.
Hence it can be noted that only 0.25 mole of ester is formed when 0.5 mole of reactants react together.
% Yield is therefore : 0.25/0.5 x 100 = 50%
Answer is C
39. From the information given above, you can note that for methane which contains only one carbon atom, ethane with two carbon atoms can be obtained as product. In other words the number of carbon atoms double.
So for propane which contains 3 carbon atoms, the resulting product may contain maximum 6 carbon atoms.
Hence we can reject the last suggestion leaving us with only 1 and 2 as potential answers.
Answer is B
Deadly_king:
--- Quote from: birchy33 on November 15, 2010, 09:48:55 am ---10. At a total pressure of 1.0 atm, dinitrogen tetraoxide is 50% dissociated at a temperature of 60 C,
according to the following equation.
N2O4 2NO2
What is the value of the equilibrium constant, Kp, for this reaction at 60oC?
A 1/3 atm
B 2/3 atm
C 4/3 atm
D 2 atm
Please explain. Its from MJ/06 P1 thank-you. Oh and please can you held with 18 and 20 from the same exam.
--- End quote ---
Jun 06 p1
10. Kp = [(NO2)]2 / (N2O4)
At equilibrium, pressure of N2O4 is while that of NO2 is 2. Since total pressure is given to be 1.0 atm, this implies that + 2 = 1.0
Therefore = 1/3, i.e pressure of N2O4 is 1/3 while that of NO2 is 2/3.
Kp = (2/3)2 / (1/3) = 4/3
Answer is C.
18. C is the most appropriate solution since it is cheaper and the reaction is not exothermic.
20. First reaction is removal of hydrogen atom, i.e oxidation of an alcohol to an aldehyde.
Second reaction is a nucleophilic reaction as an aldehyde is made to react with an alcohol to form a ketone.
Third reaction is again oxidation.
Answer is C.
birchy33:
--- Quote from: Deadly_king on November 15, 2010, 04:04:43 pm ---Jun 06 p1
10. Kp = [(NO2)]2 / (N2O4)
At equilibrium, pressure of N2O4 is while that of NO2 is 2. Since total pressure is given to be 1.0 atm, this implies that + 2 = 1.0
Therefore = 1/3, i.e pressure of N2O4 is 1/3 while that of NO2 is 2/3.
Kp = (2/3)2 / (1/3) = 4/3
Answer is C.
18. C is the most appropriate solution since it is cheaper and the reaction is not exothermic.
20. First reaction is removal of hydrogen atom, i.e oxidation of an alcohol to an aldehyde.
Second reaction is a nucleophilic reaction as an aldehyde is made to react with an alcohol to form a ketone.
Third reaction is again oxidation.
Answer is C.
--- End quote ---
Cheers mate, I'm just a bit unsure about the 2x + x = 1 bit. Secondly There's another equilibrium question: Question 9 from MJ/07. Your help would be much appreciated. Cheers + rep.
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