Chemistry: Post your doubts here!

[A*(a*)]

How to decide energy given out by various compounds on combustion, for example if we combust alcohol and ethene so which one is likely to give more energy, is only calculation energy change is the way? or we can decide through general knowledge in either case let me know the solution for it?

the greater the carbon content (C %) the higher is the energy evolved!
Alcohols have less percentage of Carbon than Alkenes, so they produce less energy.

 

[nodyed]

A CH3CH2CH2OH
B CH3CH2CH3
C CH3CH2CO2H
D CH3 COCH3

All have same no. of carbon here?

the greater the carbon content (C %) the higher is the energy evolved!
Alcohols have less percentage of Carbon than Alkenes, so they produce less energy.

 

[nodyed]

A CH3CH2CH2OH
B CH3CH2CH3
C CH3CH2CO2H
D CH3 COCH3

All have same no. of carbon here?

i got it by taking out carbon content in particular molecule right so B option gives the most carbon content (i.e. 0.8)?

 

[Nidz-Ahmed]

Organic question, help me out!?
Carboxyl compounds (aldehydes and ketones) do not make hydrogen bond within themselves Cuz The hydrogen atom is attached to Carbon , For hydrogen bond to occur ,Electronegative elements with a non bonding pair of electron available to bond with the Hydrogen that Must be attached to an Electronegative Element
Carboxyl compounds (aldehydes and ketones) do not make hydrogen bond within themselves...
Whats's the reasn behind this, i have read that for hydrogen bonding, H+ should be directly attached to (FON, i.e. fluorine, oxygen and nitrogen) but in carbonyl compounds, oxygen is have no such attachements like one should be present in H+ bonding. so is this the reason behind that?

My other confuion is i have studied that carbonyl compounds are polar right, and water is polar too?
so it is rule of thumb that polar solvents dissolves polar compunds, and non polar vice versa, exception small nonpolar compounds are soluble in water?
okay, so now the confusion is according to this rule aldehydes and ketones should be soluble in water, but they are sonly soluble with small chains of carbon, in bgger chains they are insoluble, so why is this soo??

Any kind of help will be appreciated, please help me!

 

[nodyed]

?

 

[A*(a*)]

i got it by taking out carbon content in particular molecule right so B option gives the most carbon content (i.e. 0.8)?

Yes I think so B is the ans, because it has the greatest percentage of Carbon

 

[nodyed]

ty u remind me, i totally forgot that!

 

[A*(a*)]

i got it by taking out carbon content in particular molecule right so B option gives the most carbon content (i.e. 0.8)?

the % is 85.7. Your O'levels teacher told you about this, Didn't you remember?

 

[nodyed]

u r ryt i was just checking roughly without multiplying by hundred ! so it was something 0.857, as it was mcq, yep now you remind me

 

[A*(a*)]

u r ryt i was just checking roughly without multiplying by hundred ! so it was something 0.857, as it was mcq, yep now you remind me

Do you know who I am? :

 

[nodyed]

Do you know who I am? :

i guess ali dk no profile pic, how can i know

 

[A*(a*)]

i guess ali dk no profile pic, how can i know

Hamza

 

[Nidz-Ahmed]

?

Sorry was in a hurry
Uhm thats your answer

Carboxyl compounds (aldehydes and ketones) do not make hydrogen bond within themselves Cuz The hydrogen atom is attached to Carbon , For hydrogen bond to occur ,A Electronegative elements with a non bonding pair of electron (lone pair) must be available to bond with the Hydrogen that Must be attached to an Electronegative Element
And its soluble Cuz Carboxyl Compounds can form hydrogen bonds with water but with themselves

 

[Abu mota]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s07_qp_1.pdf
Q.36
The answer is D, i know that the first one is correct and that the 2nd one is wrong but the third statement to me looked ok, so i just said A. Now my question is: why is statement 3 wrong?

 

[darknessinme]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s07_qp_1.pdf
Q.36
The answer is D, i know that the first one is correct and that the 2nd one is wrong but the third statement to me looked ok, so i just said A. Now my question is: why is statement 3 wrong?

You know option 1 is correct and option 2 is incorrect so that's fine.
Option 3 suggests Astatine is a good reducing agent. IF it was a reducing agent, then the Astatine molecules would get oxidised in the process, but what can they get oxidised to? They can't turn into At+ ions or increase their oxidation state. So that's why option 3 is incorrect. I would assume though that At- ions are good reducing agents.

 

[nodyed]

h

Hamza

hamza tariq ryt?

 

[nodyed]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s08_qp_1.pdf
q.29, how chiral and what feature decides about acidic or alkaline?

 

[NIM]

How to prepare solutions of different concentration???

 

[haha101]

hey this is a question for everyone ! how many MCQ's do you guys get wrong per paper ?

 

[haha101]

How to decide energy given out by various compounds on combustion, for example if we combust alcohol and ethene so which one is likely to give more energy, is only calculation energy change is the way? or we can decide through general knowledge in either case let me know the solution for it?

dude another way to look at this is by checking the no of oxygen . if it has no oxygen then it wall release the most amount of energy for eg : hydrocarboons with no oxygen attached will give out more energy then those with oxygens attached . Btw yeh baat call pr q nh pooochi