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yeah because making all the structures is going to be time consuming..but thanks a lot!
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Yes, takes 3-4 minutes!yeah because making all the structures is going to be time consuming..but thanks a lot!
thnx..il post the link.. sorry..Heating under reflux means heating without having the risk of the liquid evaporating or splashing off the flask
A liebag condenser condenses the evaporaing liquid back into the flask
A Request:
Plz post the link to your questions
First write the balanced equation.what volume of oxygen ,measured at room temperature and pressure,is required for the complete combustion of 8.65g of H2S ?
plzz help..howz this done..??
4)need help with June 2010 paper1 Q 4,6,21,29,40
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_11.pdf
4)
thanks a lot!For question 4
Maybe somebody else can verify this, i'm not so sure:
First you try to write an equation for the reaction, which is as follows:
SO2 + I- ----> I2 + SO42-
Then, you find the oxidation numbers of S in SO2 and SO42-and you'll see a change from +4 to +6.
So the answer is D
For question 9
First you find the ▲H = 200 x 4.2 x (66-18) =40320 Jg-1oC-1
Let the energy released when 1.60 g of fuel is burned be x J
0.45x has been absorbed by 200g of water
So, 0.45x = 40320
Hence x = 89600 J
Now, When 1.60g is burned, 89600 J of energy is released
So, when 1g of fuel is burned, 89600/1.60 = 56000 J of energy is released.
Answer is B.
Hope my answer has been of help to you.
thank you so much!! its amazing how you guys help others! God bless you4)
P - One Br-Br bond is breaking. So enthalpy change is -193J
Q - One Cl-Cl bond is forming. So enthalpy change is +244J
R - One C-Cl bond is forming. So enthalpy change is +340J
S - One C-H bond is breaking. So enthalpy change is -410J.
Answer is therefore D.
6) NH4NO3 is really NH4+ and NO3-.
Oxidation state of N in NH4+:
x + 4 = +1
x = -3
Oxidation state of N in NO3- :
x + (-2 x 3) = -1
x = +5
Oxidation state of N in N2O:
2x + (-2) = 0
x = +1
So changes in oxidation numbers are:
-3 ---> +1 = +4
+5 ---> +1 = -4
Answer is D
21) Here, they're testing your knowledge of what happens in a free radical substitution reaction. A C-H bond is changed to a C-Cl.
In the compound given, work clockwise with the carbon atoms. In the top most carbon atom, any of the hydrogens being replaced will give the same X radical. So this gives one possible X radical. The next two carbons will also have only one possible distinct replacement. However, these replacements will give radicals which are identical to the replacement given by the first carbon. Try doing this on a paper if you don't get how.
Another possible replacement is on any one of the 2 hydrogens on the second-last carbon on the left. The last one is possible on any one of the 3 hydrogens on the last carbon.
Hence a total of 3 possible X radicals are possible. Ans: C
29) butan-2-ol can form only 2 straight chain alkenes plus one alkene with an alkyl side chain. Ans: B
40) in 3 both reactants are gases. They can't be 'heated under reflux'. Ans: B
For question 4
Maybe somebody else can verify this, i'm not so sure:
First you try to write an equation for the reaction, which is as follows:
SO2 + I- ----> I2 + SO42-
Then, you find the oxidation numbers of S in SO2 and SO42-and you'll see a change from +4 to +6.
So the answer is D
Aoa,Need help with Question 3 on this paper: (Summer 2011 Qp 21)
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_21.pdf
What topic is it? Is it Group 2? I couldn't get any answers correct from Question 3 C till the end of the question. Help me. Exam is in less then a month.
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