Is this answer correct? (1 Viewer)

[eternallyboreduser]

 

[eternallyboreduser]

bump

 

[eternallyboreduser]

bump

 

[Pre-life]

I think you would need to mention electron density and say that since Cl is quite large, it would have lower electron density and thus cannot form h bonds. Because it is electron density that determines whether h bonds can be formed or not, rather than the atomic radii.

 

[eternallyboreduser]

I think you would need to mention electron density and say that since Cl is quite large, it would have lower electron density and thus cannot form h bonds. Because it is electron density that determines whether h bonds can be formed or not, rather than the atomic radii.

Hmm, i have not yet learnt about electron density in module 1

 

[Luukas.2]

The part about Cl's radius is correct, the parts about "nearly stealing" electrons from H is not. In an H-bonding situation, the H atom is interacting with two very electronegative atoms - one through a covalent bond, one through an electrostatic interaction (the H-bond). The electron from the H atom is part of the covalent bond to the N, O, or F to which it is bonded, and not to the N, O, or F to which it is H-bonded. What can be stolen is the nucleus of the H atom (as a proton) which can be transferred from one species to another, as you will see repeatedly in Module 6. One example would be when ammonia dissolves in water: the H-bond between an ammonia molecule (with the lone pair on the N as the H-bond acceptor) and water can result in transfer of the H⁺ to the ammonia, forming an ammonium ion and a hydroxide ion:

H₃N:......H-OH ------> [H₃N--H]⁺ + OH^-
​

where the line of yellow dots (......) is meant to represent the H-bond, and the green lone pair becomes a green (coordinate) covalent bond as the proton (H⁺) is "stolen" from the water molecule.

 

[eternallyboreduser]

The part about Cl's radius is correct, the parts about "nearly stealing" electrons from H is not. In an H-bonding situation, the H atom is interacting with two very electronegative atoms - one through a covalent bond, one through an electrostatic interaction (the H-bond). The electron from the H atom is part of the covalent bond to the N, O, or F to which it is bonded, and not to the N, O, or F to which it is H-bonded. What can be stolen is the nucleus of the H atom (as a proton) which can be transferred from one species to another, as you will see repeatedly in Module 6. One example would be when ammonia dissolves in water: the H-bond between an ammonia molecule (with the lone pair on the N as the H-bond acceptor) and water can result in transfer of the H⁺ to the ammonia, forming an ammonium ion and a hydroxide ion:

H₃N:......H-OH ------> [H₃N--H]⁺ + OH^-
​

where the line of yellow dots (......) is meant to represent the H-bond, and the green lone pair becomes a green (coordinate) covalent bond as the proton (H⁺) is "stolen" from the water molecule.

Yeah so what i’m saying is that the electron in the covalent bond is “nearly stolen” by the F/O/N atom from the hydrogen atom leaving the hydrogen atom as just a bare nuclei with an extremely concentrated positive charge which allows for large partial charges to form and increases the polarity of the molecule. This allows for stronger H-bonds to form.

 

[xoNat]

Why do you answer in red

 

[eternallyboreduser]

Why do you answer in red

Didnt have a blue or black pen present

 

[Luukas.2]

Yeah so what i’m saying is that the electron in the covalent bond is “nearly stolen” by the F/O/N atom from the hydrogen atom leaving the hydrogen atom as just a bare nuclei with an extremely concentrated positive charge which allows for large partial charges to form and increases the polarity of the molecule. This allows for stronger H-bonds to form.

Good, but that's not how it sounded when I read it.

Also, there is a second factor here that none of the above has addressed. Atomic radius and reduced charge density explains why Cl atoms are generally ineffective as H bond acceptors, but what about the other side of the H bond?

What I would want to see for 2 marks for this question would depend on where it was asked. If it was a trial, or worth more, there is more I would want to see.

 

[eternallyboreduser]

Good, but that's not how it sounded when I read it.

Also, there is a second factor here that none of the above has addressed. Atomic radius and reduced charge density explains why Cl atoms are generally ineffective as H bond acceptors, but what about the other side of the H bond?

What I would want to see for 2 marks for this question would depend on where it was asked. If it was a trial, or worth more, there is more I would want to see.

It’s just a revision booklet for the tutoring y11 module 1 chem exam i have in 2.5 weeks

 

[Luukas.2]

It’s just a revision booklet for the tutoring y11 module 1 chem exam i have in 2.5 weeks

Then it is likely that the answer they seek is the one you have - that despite its higher electronegativity, the much greater radius of chlorine results in a charge density that makes for a poorer H-bond acceptor when compared to nitrogen.

There is material in modules 6 and 7 that will be relevant to this point later on, though.

Preparing for a module 1 test is an even stronger reason for questions to avoid atypical cases like AlCl₃, by the way.

 

[eternallyboreduser]

Then it is likely that the answer they seek is the one you have - that despite its higher electronegativity, the much greater radius of chlorine results in a charge density that makes for a poorer H-bond acceptor when compared to nitrogen.

There is material in modules 6 and 7 that will be relevant to this point later on, though.

Preparing for a module 1 test is an even stronger reason for questions to avoid atypical cases like AlCl₃, by the way.

Oh okay, so for that ruse prelim yearly q , i shouldn’t have to worry about it?

 

[Luukas.2]

Oh okay, so for that ruse prelim yearly q , i shouldn’t have to worry about it?

Badly written questions are sadly common, as are questions with mistakes. You will find them from time to time, just hope it's not in an important assessment. The 2023 had three mistakes, IIRC, though hopefully none made any difference.

 

[Luukas.2]

@jimmysmith560, perhaps this thread belongs in the Chemistry forum?

 

[Luukas.2]

View attachment 41550

Might I also note that your answer wastes 2 of the 7 lines in restating the question, and doesn't actually specify what is needed for an H-bond. You clearly know what is needed, but have assumed part of it without actually saying it.

Also, consider what you would include if the question was worth 5 marks.