Chemistry MCQ thread...

[Zishi]

Explanation???

W has both nitrile and hydroxyl groups. X has carboxyl group only, I guess. So potassium dichromate and Na can be used to distinguish between them. As for AgNO3, I think it's for something relating to benzene ring(it's not ins syllabus). As 1 and 3 are correct, so obviously A is the answer.

The explanation is messy. So wait for it.

 

[hassam]

 

[Hateexams93]

which of the following least resembles an ideal gas : ammonia or trichloromethane , can some1 plz expain why its not CHCl3?????

 

[hassam]

on adding HCN we have a product containing CN and OH....product in last step tell us that an amine is formed....and if u remember halogenoalkanes chapter that amines are formed from them by heating in a sealed tube...so from here we get that X contains HALOGEN....now i guess its too easy for all of u to guess y A shud be the anser

 

[MHHaider707]

Is it B???

which of the following least resembles an ideal gas : ammonia or trichloromethane , can some1 plz expain why its not CHCl3?????

Ammonia!!!

Ammonia have hydrogen bonding due to which it will deviate largely from an ideal gas behavior!!

 

[hassam]

although trichloromethane is larger than ammonia....but since ammonia has the MIGHTY H BONDS...so no need to look at trichloromethane with weak dipole interactions

 

[Zishi]

I did this swiftly, so I get C as the answer. Don't tell the answer til I'm confirmed with my answer.

EDIT: I think I'm sure that C is the answer. What does the mark scheme say?

 

[xHazeMx]

on adding HCN we have a product containing CN and OH....product in last step tell us that an amine is formed....and if u remember halogenoalkanes chapter that amines are formed from them by heating in a sealed tube...so from here we get that X contains HALOGEN....now i guess its too easy for all of u to guess y A shud be the anser

how amine is formed from a chloroalkane for example after heating in a sealed tube????

 

[MHHaider707]

I think its B!!

 

[hassam]

sadly i dont have markscheme....btw a convvincing explanation wud work for me

 

[Zishi]

-_- I'm pretty sure that the answer has to be C. First confirm it please, if I'm right - then I'll tell my explanation...

 

[hassam]

sadly i dont have markscheme for this particular one....btw a convvincing explanation wud work for me

 

[Zishi]

on adding HCN we have a product containing CN and OH....product in last step tell us that an amine is formed....and if u remember halogenoalkanes chapter that amines are formed from them by heating in a sealed tube...so from here we get that X contains HALOGEN....now i guess its too easy for all of u to guess y A shud be the anser

how amine is formed from a chloroalkane for example after heating in a sealed tube????

By heating it with ethanolic concentrated ammonia.

 

[Zishi]

sadly i dont have markscheme for this particular one....btw a convvincing explanation wud work for me

Which exam board is it? I may get the mark scheme.

 

[hassam]

....its a book with me...saved...as pdf

 

[xHazeMx]

thx zishi,
can u explain ur attempt to the last question?

 

[xHazeMx]

can some one explain choice no. 1 in Q 34 , June 2002

 

[hassam]

zishi......???

 

[MHHaider707]

can some one explain choice no. 1 in Q 34 , June 2002

Choice no. 1 is wrong....rite??

With increase in temp. Kp value increases which means that with an increase in temp. there is an increase in yield!!!!

And we knw that if the yield of reaction increase on increase in temp. then reaction is endothermic but in 1 it says reaction is exothermic so 1 is wrong!!

 

[Zishi]

....its a book with me...saved...as pdf

The explanation is a bit lengthy hassam. I'll tell you about it within 30 minutes.