Solubility of ions compared to H-bonding question

[dedicate]

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When I answered this question I reasoned that the N-H in A would H bond therefore it was the most soluble, but the answer was that the quaternary salt was the most soluble.

Why is this and why is it that ions in general are more soluble?

 

[computerdorkdan]

When I answered this question I reasoned that the N-H in A would H bond therefore it was the most soluble, but the answer was that the quaternary salt was the most soluble.

Why is this and why is it that ions in general are more soluble?

I think it's because they have a charge. Something with a charge is going to be more soluble in a polar protic solvent than something without a charge.

 

[football9315]

There are 2 reasons why C is the correct answer.

1) C has a hyrogen attached to an electronegative element (nitrogen)

2) But mainly, it has a positive charge. Positive charges and polar molecules are most soluble in polar solvents such as water

This isnt the best question in the world b/c A seems like a feasible choice due to its lone pair of electrons and hydrogen atom.

I wouldnt worry so much about this particular question, as it is sort of ambiguous. Just know that for solubility..

a) like dissolves like (polar dissolves polar)
b) Hydrogen bonding is one of the reasons a molecule may dissolve in water (or another hydrophilic solvent)
C) hydrophilic solvents like water dissolve charged molecules (ie NaCl) b/c it is entropically driven

 

[dedicate]

Thanks for the info.

What is the basis behind water strongly dissolving charged molecules? Can you expound on that please?

 

[computerdorkdan]

Thanks for the info.

What is the basis behind water strongly dissolving charged molecules? Can you expound on that please?

Water is polar. Oxygen is slightly negative and the hydrogens are slightly positive. In this case the oxygen would associate easily with the positive charge, surrounding, or solvating (sp?) the nitrogen molecule. It would help make the positive charge slightly less positive, an energetically favorable action. Although, for this situation hydrogen bonding is much more important.

 

[dedicate]

Water is polar. Oxygen is slightly negative and the hydrogens are slightly positive. In this case the oxygen would associate easily with the positive charge, surrounding, or solvating (sp?) the nitrogen molecule. It would help make the positive charge slightly less positive, an energetically favorable action. Although, for this situation hydrogen bonding is much more important.

Thanks that helps, although the answer indicated that the salt was more soluble than the H-bonding for answer A.