Chemistry MCQ thread...

[MHHaider707]

Yeah its B.... but how...??

 

[xHazeMx]

Yeah its B.... but how...??

bond energies

 

[sakibfaiyaz]

Yeah, there should be a choice of 107*...

wat abt Q. 9 and 38??

Ok I guess 9 is common sense...C and D wont be the answer (acids and ketones are not used as fuels)...
and i guess we know it from bio that a substance which is richer in Carbon-hydrogen bonds has a greater calorific value(its a fact so you can learn it).so the answer should be B

 

[xHazeMx]

check the bond energies of each compound. the greatest bond energies will release the greatest energy

 

[xHazeMx]

answer with explaining

 

[hassam]

YA ITS a...H2S...WITH A BOND ANGLE OF 92 Deg!!!

 

[hassam]

all 3....that is A....ITS SIMPLE....2nd one is a characteristic acid-base reaction....and 3rd one a characteristic reaction of ammonium salts with alkalis...
talking abt 1st reaction....well CO2 is present in soil just like oxygen is found....so CO2....AN ACIDIC oxide...will again undergo acid base reaction

 

[xHazeMx]

all 3....that is A....ITS SIMPLE....2nd one is a characteristic acid-base reaction....and 3rd one a characteristic reaction of ammonium salts with alkalis...
talking abt 1st reaction....well CO2 is present in soil just like oxygen is found....so CO2....AN ACIDIC oxide...will again undergo acid base reaction

just had a confusion about 1. thanks

 

[hassam]

14 Which of the following is the strongest reducing agent?
A Ba B Ba2+ C Mg D Mg2+

 

[xHazeMx]

14 Which of the following is the strongest reducing agent?
A Ba B Ba2+ C Mg D Mg2+

C ?

 

[xHazeMx]

why 2 is wrong ?

 

[Anonymousx3]

why 2 is wrong ?

I was wondering the same thing.
This is what it says in the ER:

"The most surprising response came in Q40, in which candidates were asked to identify those products of the hydrolysis of methyl butanoate, CH3CH2CH2CO2CH3, with NaOH (aq) that would be in a subsequent distillate. Whereas 80% correctly identified CH3OH, 70% thought that the salt, CH3CH2CH2CO2Na, would have distilled over."

What I gathered from that is, CH3CH2CH2CO2Na will not be present in the distillate.

 

[Anonymousx3]

14 Which of the following is the strongest reducing agent?
A Ba B Ba2+ C Mg D Mg2+

I think it's A, but I'm not completely sure.

 

[xHazeMx]

why 2 is wrong ?

I was wondering the same thing.
This is what it says in the ER:

"The most surprising response came in Q40, in which candidates were asked to identify those products of the hydrolysis of methyl butanoate, CH3CH2CH2CO2CH3, with NaOH (aq) that would be in a subsequent distillate. Whereas 80% correctly identified CH3OH, 70% thought that the salt, CH3CH2CH2CO2Na, would have distilled over."

What I gathered from that is, CH3CH2CH2CO2Na will not be present in the distillate.

alright then, a new info to add to our brains

 

[xHazeMx]

why it is not D !!

 

[Anonymousx3]

why it is not D !!

Esters don't mix completely with water.
The small esters are fairly soluble in water but solubility falls with chain length.

 

[Abdulrab]

use of data booklet is relevant to this question !
What mass of solid residue can be obtained from the thermal decomposition of 4.1 g of anhydrous calcium nitrate ?
A. 0.7g
B 1.00g
C 1.40g
D 2.25g

i am getting C !! but it is not correct !! please give the answer with full working ! thnx

 

[hassam]

ya that was A barium..cos reducing agent has to loose e- and the most effective reducing agent wud be one with lowest I.E

 

[Zishi]

use of data booklet is relevant to this question !
What mass of solid residue can be obtained from the thermal decomposition of 4.1 g of anhydrous calcium nitrate ?
A. 0.7g
B 1.00g
C 1.40g
D 2.25g

i am getting C !! but it is not correct !! please give the answer with full working ! thnx

The answer has to be C. Does mark scheme say that C is wrong?

 

[smartangel]

please help me with june 06 question 38.