Chemistry: Post your doubts here!

[princess Anu]

How? can you please elaborate..

Oxidation of the third one produces two compounds.

 

[Rohaan Nadeem]

In the third compound, there is a lenghty carbon chain and a primary alcohol (they are attached)
Now when CH3CH2(CH3)CH2- is oxidised, a ketone is formed and when a primary alcohol is oxidised, a carboxilic acid is formed.
Therefore, oxidation(gain of oxygen) breaks this compound into two compounds.

 

[princess Anu]

Well, I just checked the marking scheme and the answer is A :s

In the third compound, there is a lenghty carbon chain and a primary alcohol (they are attached)
Now when CH3CH2(CH3)CH2- is oxidised, a ketone is formed and when a primary alcohol is oxidised, a carboxilic acid is formed.
Therefore, oxidation(gain of oxygen) breaks this compound into two compounds.

 

[Rohaan Nadeem]

Can't be!!!
Let ,me review again!

 

[princess Anu]

Yes please..

 

[rexsun]

First question

The answer, as the mark scheme says, is B. I chose A and got it wrong..Can anybody kindly explain a bit about that please!!!


The Second one

Could anybody explain how to decide the bond angle in this case? D can be ruled out because N has lone pairs, but for the remaining three , I feel hard.

The third, most important one

Answer is A. What@!? HSO3- act as a base in the second reactoin???? I feel just totally baffled...

OK, the last one, thanks guys for being so patient

The answer is A... But I feel D seems to be more correct. Potassium forms covalent bonding in most cases, thus it should show the greatest tendency... Not sure if I have misunderstood the question however.

 

[RoOkaYya G]

1st one -_- too lazy to read all tht sorry :S

2nd one is : the nitrogen, having a double bond to the adjacent carbon and a single bond to the methyl group, is sp^2 hybridized and, therefore, the C-N-C bond angle would be 120°.

3rd one : the HNO3 - acts as a base as it neutralises the H+ (acidic)

4th one : its aluminium since its cation is Al3+ it has 3 electrons free to make covalent bonds unlike Mg2+ Ne (noble gas) K+
rexsun

 

[RoOkaYya G]

First question

The answer, as the mark scheme says, is B. I chose A and got it wrong..Can anybody kindly explain a bit about that please!!!


The Second one

Could anybody explain how to decide the bond angle in this case? D can be ruled out because N has lone pairs, but for the remaining three , I feel hard.

The third, most important one

Answer is A. What@!? HSO3- act as a base in the second reactoin???? I feel just totally baffled...

OK, the last one, thanks guys for being so patient

The answer is A... But I feel D seems to be more correct. Potassium forms covalent bonding in most cases, thus it should show the greatest tendency... Not sure if I have misunderstood the question however.

PS i think for quest 1 its A

 

[neha saleem]

papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20%289701%29/9701_w05_qp_4.pdf

can sum1 pls help wid q2 d..........

 

[rexsun]

1st one -_- too lazy to read all tht sorry :S

2nd one is : the nitrogen, having a double bond to the adjacent carbon and a single bond to the methyl group, is sp^2 hybridized and, therefore, the C-N-C bond angle would be 120°.

3rd one : the HNO3 - acts as a base as it neutralises the H+ (acidic)

4th one : its aluminium since its cation is Al3+ it has 3 electrons free to make covalent bonds unlike Mg2+ Ne (noble gas) K+
rexsun

Thanks so much! Though I still don't quiet understand what's meant by SP^2 and why it's 120 degree. Anyway I will find out.Thanks

 

[RoOkaYya G]

Thanks so much! Though I still don't quiet understand what's meant by SP^2 and why it's 120 degree. Anyway I will find out.Thanks

quite*

well it is the hybridisation level. u've studied hybridisation yet?

 

[neha saleem]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s06_qp_4.pdf

q 5 c.....hw is it amine...........

 

[Rohaan Nadeem]

Yes please..

I just reviewed my notes and you're right.
I drew the first one correct.
The second compound is an aldehyde and aldehydes, under harsh conditions can be oxidised into Carboxilic Acids, so if Y is (CH3)3CCH2CH2OH, (C6H14O) Z would be (CH3)3CCH2COOH (C6H12O2).Same reason goes for the third compound.

 

[Rohaan Nadeem]

A

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_4.pdf

q 5 c.....hw is it amine...........

Amine group is C-NH2,

 

[neha saleem]

thanxx............

cn u pls show hw to do q2 c iii.....
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_42.pdf

 

[princess Anu]

Why is the answer to this B and not A?

 

[Rohaan Nadeem]

thanxx............

cn u pls show hw to do q2 c iii.....
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_42.pdf

 

[Rohaan Nadeem]

Why is the answer to this B and not A?

Reaction 1 is decomposition and decomposition reactions are always endothermic. That heating upto 1000 degrees Celcius was an absolute hint too.
Reaction 2 involves braking of a lattice and formation of Ca-OH bonds. If you use a data booklet, you will see that enthalpy of -OH ion is less than the enthalpy of -O.

 

[princess Anu]

what does that imply?

Reaction 1 is decomposition and decomposition reactions are always endothermic. That heating upto 1000 degrees Celcius was an absolute hint too.
Reaction 2 involves braking of a lattice and formation of Ca-OH bonds. 'If you use a data booklet, you will see that enthalpy of -OH ion is less than the enthalpy of -O'.

 

[Rohaan Nadeem]

Aren't you aware that we are provided with data booklets that have value of certain bonds printed.