Help needed on Chemistry MCQ's!

[Ash1994]

Okay. .so i solved this paper and I want to know the reason's behind the question's that i got wrong!
I DID HORRIBLE! >__< So, Basically, I'm in deep water. . So it would be really kind of anyone who can help

http://www.xtremepapers.me/CIE/Internat ... 7_qp_1.pdf

Q, 6,7,8,9,10,12,18,19,20,21,22,23,29,30,32,34,35,36,37,40!!!!!!!
Yes, I got a whole bunch of questions wrong

 

[sweetiepie]

Q. 22 is A
ALKENE + HALOGEN -------> CARBONIUM ION
CH2=CH2 + BR2---> CH2BRCH2BR

get it..

 

[ExoticPlayer09]

10:
We know that when we increase the temp. the curve gets steeper and it's peak decreases.Overhere they gave a dist. of a high temp and they are asking for the graph of a low temp. so simply, at lower temp. the peak will increase(L) and the steepnes will decrease( M and N)..

 

[ExoticPlayer09]

19:
It has 4 chiral centres, 2nd, 3rd, 4th and 5th C-atom.They all are attached to different groups.So therefore, thyr are 4-chiral centres.

 

[ExoticPlayer09]

20:
In this see, F is substituted, cl^3 is reduced to cl^2 and an F is substituted inplace of 1 cl..So its answer is D, nucleophilic substitution.

 

[Ash1994]

19:
It has 4 chiral centres, 2nd, 3rd, 4th and 5th C-atom.They all are attached to different groups.So therefore, thyr are 4-chiral centres.

But isn't the 2nd one attached to 2 carbon atoms?
Chiral centres are one''s in which there are 4 diff groups ryt?

 

[ExoticPlayer09]

Yeah it is but also check what is attached to that C-atoms..Like to the first --H and that ==o, is different from the 2nd one --H and ---OH

 

[ExoticPlayer09]

6:
Its D because only OH has Hydrogen-Bonds

 

[ExoticPlayer09]

7:
It says ''Intermediate'', so there will be ''2-Peaks''. A and B are eliminated because they just have 1-peak.
In C if you check the first peak, its at 50 and in the question it says that THE ACTICATION ENERGY OF STAGE 1 IS 5O KJMOL-1. And if you check the overall enthalpy change, its -100-0, so its -100KJMOL-1.

D cant be because in D the Energy for stage 1 is aound 75-100 and they said in the question that its 50KJMOL-1. So D cant be the answer, Its C

 

[ExoticPlayer09]

12:
Its B because MgCl2 is smaller in size and has a greater charge.
NaCl has ionic-bonding,
AlCl3 has covalent-bonding,
and SiCl4 has simple-covalent-bonding.
So the answer is B.

 

[ExoticPlayer09]

18:
Its D because Ammonium-Nitrate will form Ammonia Gas which will in-turn the pH paper Blue.

 

[ExoticPlayer09]

29:
Its C because only Ethanal can undergo Nucleophilic-Addition.

 

[ExoticPlayer09]

32:
Brass has only Metallic-Bonding,
Graphite has weak-van-der-wall's forces and Covalent bonding and so does Ice, it has H-Bonds etc.
So the answer is C

 

[ExoticPlayer09]

35:
Its D because, 2 and 3 are wrong, Why, because SiO2 is also inslouble in water(2) and the maximum oxidation is not shown by Silicon, Cl has a higher Oxidation state.