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Chemistry: Post your doubts here!

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Metallic9896

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ughkno said:
can one of you help me with this? I can't understand why the answer is B - thanks
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1 is true cause of the COOCH3 branch, it's an ester, so H2SO4 will hydrolyze it.
2 is true cause again, COOCH3 is an ester, alkaline hydrolysis of esters will occur due to NaOH.
3 not true cause no open OH or OOH with which sodium metal can react.
 
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ughkno

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Metallic9896 said:
1 is true cause of the COOCH3 branch, it's an ester, so H2SO4 will hydrolyze it.
2 is true cause again, COOCH3 is an ester, alkaline hydrolysis of esters will occur due to NaOH.
3 not true cause no open OH or OOH with which sodium metal can react.
Click to expand...
Thanks! It had an easy logic but I messed up.
 
Z

zellyman

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Metallic9896 said:
Damn. I talked to a friend (absolute genius) and he pointed out that it's perhaps cause CO doesn't get oxidized in the atmosphere. Which would make sense cause normally you see that when CO is produced, it like, remains in the air ya know. It harms us and stuff. Unlike NO which we do in paper 3 which 'readily oxidized to NO2' when in contact with air. I presume the same goes for sulphur. Hence why carbon is rejected.
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I guessed something of the sort,its its still an ill demeanor to give us questions as such,since from our O levels we know that CO is a powerful reducing agent and so there is still a possibility of it being oxidised in the atmosphere.
 
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Metallic9896

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3 guys from my batch said 2015 Paper 12 is hard and they got 27-28 ish, give it a shot. I'll give it a try too.
 
SohaibButt

SohaibButt

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ANYONE?
 

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Metallic9896

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SohaibButt said:
ANYONE?
Click to expand...

1. It's B cause when the HBr is eliminated and C=C forms, the second C (the one which had the Br) can either form a C=C with the C to its left (the first C), OR form a C=C with the C to its right (i.e., C=C between 2nd and 3rd C). This is 2 structural isomers. Then for the C=C in the middle formed by the 2nd and 3rd C, there will be cis-trans isomerism. So total, 3 isomers. It's not the case in any other option.
 
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Metallic9896

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SohaibButt said:
ANYONE?
Click to expand...

2. Both exist as solid lattice. You should know that I2 is a solid molecular lattice, google it. But you can also get A by eliminating the other incorrect options. It can't be B cause SiO2 is a giant molecular structure, not simple. It can't be C cause CO2 has double bonds. It can't be D cause SiO2 doesn't sublime at room temp. at all as it has a very high melting point and it'd go liquid before going gas. So only A is left which must be true.
 
D

darks

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Any tips for structural isomers etc?
for cis trans... "2^no of double bonds"
for optical... "2^no of chiral carbons"
for stereoisomers... "2^no of chiral carbons+double bonds"
The double bonds are of of course cis trans C=C only.
 
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Metallic9896

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darks said:
Any tips for structural isomers etc?
for cis trans... "2^no of double bonds"
for optical... "2^no of chiral carbons"
for stereoisomers... "2^no of chiral carbons+double bonds"
The double bonds are of of course cis trans C=C only.
Click to expand...

Hmm yeah these are good formulae but there are exceptions so I just do the counting on the spot lol and I leave isomers for the end so that's a major tip. Skip isomer questions. Do em at the end. XD
 
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Metallic9896

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SohaibButt said:
ANYONE?
Click to expand...

3.

R to S is -134
S to R is +134
S to U is +92
U to S is -92
U to T is -75
T to U is +75

Statement 1: U to R = U to S + S to R = -92 + 134 = +44 so it's true
Statement 2: T to S = T to U + U to S = +75 + -92 = exothermic, not endothermic
Statement 3: Knowing that 2 is incorrect and 1 is correct, you can jump for D as the answer cause there is no '1 and 3', but just to prove that 3 is incorrect, R to T = R to S + S to U + U to T = -134 + 92 + 75 = +33, while they say -33, so incorrect.
 
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