Chemistry: Post your doubts here!

[darks]

can one of you help me with this? I can't understand why the answer is B - thanks

Both 1, and 2 will cause hydrolysis of the ester group. Na does not react with any group present.

 

[ughkno]

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.

Thanks! It had an easy logic but I messed up.

 

[zellyman]

can one of you help me with this? I can't understand why the answer is B - thanks

Hydrolysis of the ester bond by dilute Sulfuric acid or Sodium hydroxide is possible ^_^

 

[zellyman]

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.

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.

 

[Metallic9896]

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.

 

[darks]

View attachment 62499
Classic.

0.002 : p

 

[SohaibButt]

ANYONE?

 

[SohaibButt]

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.

Man also do march 2016

 

[darks]

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.

Yeah it has some really tricky Qs, must solve.

 

[Metallic9896]

ANYONE?

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.

 

[Metallic9896]

ANYONE?

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.

 

[darks]

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.

 

[Metallic9896]

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.

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

 

[darks]

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

I hope they don't come, or the easier ones come

 

[Metallic9896]

ANYONE?

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.

 

[darks]

GOOD LUCK GUYS!! I am out now! I hope we all nail the exam!

 

[Metallic9896]

I hope they don't come, or the easier ones come

Ikkk same, like today there was no EPG lol

 

[Metallic9896]

GOOD LUCK GUYS!! I am out now! I hope we all nail the exam!

Haha good luck to you too man I really hope we do! Have a goodnight, I'll be up!

 

[Metallic9896]

Guys what's going on in this one?

 

[Metallic9896]

ANYONE?

4.
A: D without a charge has 1 proton and 1 neutron and 1 electron. D- would have 1 proton 1 neutron 2 electrons, so it has more electrons than protons but not more protons than neutrons.
B: H3O without a charge has 10 protons 10 electrons and 8 neutrons, with + charge it loses 1 electron and has 9 electrons 10 protons 8 neutrons, so it has more protons than neutrons but not more electrons than protons.
C: OD without charge has 9 protons 9 electrons and 9 neutrons, after - charge has 10 electrons 9 protons 9 neutrons, more electrons than protons but not more protons than neutrons.
D: OH without charge has 9 protons 9 electrons and 8 neutrons, after - charge has 10 electrons 9 protons 8 neutrons, which fulfills conditions, making it ther ight answer.