Polar Covalent Bond in HCl question

In summary, the polar covalent bond in HCl creates a polar molecule because the molecule is unsymmetrical. This means that the partially positive H can attract negative ions and the partially negative Cl can attract positive ions from another compound.
  • #1
If my understanding is correct, the polar covalent bond in HCl creates a polar molecule because the molecule is unsymmetrical.

1. Does this mean that the partially positive H of one HCl molecule will be attracted to the partially negative Cl of another HCl molecule and vice versa, to create a chain of HCl? If so, what is this called?

2. In regards to an HCl molecule, does this also mean that the partially positive H can attract negative ions and the partially negative Cl can attract positive ions from another compound such as KCl?
 
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  • #2
1. I'm assuming you are talking about hydrogen bonding-like behavior. In that sense, it sort of happens but the attraction is much much smaller than e.g. oxygen and nitrogen. This is because although chlorine have high electronegativity, due to its atom size, the electron density is not high enough for hydrogen bonding. As such, it's improbable that it creates a chain of HCl.

2. Due to the reason above, I don't think you can observe a hydrogen bond-like behavior or significant attraction for chlorine atom in HCl. The dipole attraction do happen to some extent though, and this affects the boiling point. As for hydrogen bond for the hydrogen in HCl, hydrogen bond between fluorine of HF and hydrogen of HCl has been documented before (HF-HCl complex).
https://aip.scitation.org/doi/abs/10.1063/1.434691
 
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  • #3
Got it! Thanks:biggrin:
 
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ProjectFringe said:
If my understanding is correct, the polar covalent bond in HCl creates a polar molecule because the molecule is unsymmetrical.

1. Does this mean that the partially positive H of one HCl molecule will be attracted to the partially negative Cl of another HCl molecule and vice versa, to create a chain of HCl? If so, what is this called?
It probably does not happen, but if it does, it would be called "associate".
Compare HF. HF has molar mass of 20. It boils at +19 Celsius. And even above the boiling point, the molar mass of vapour is much bigger than 20, non-integer and varies strongly with temperature and pressure - at room temperature it is around 50 or so. The reason is that the vapour has equilibrium of various hydrogen bonded associates - (HF)2, (HF)3, some HF and so on, which equilibrium easily shifts.
In contrast, HCl boils at -85, and the vapour seems to be mostly lone molecules.
The reason is that H is much smaller than Cl. With the smaller F, H can give both polar covalent bond and hydrogen bond. With Cl, the polar covalent bond is weaker, and hydrogen bond cannot be formed.
ProjectFringe said:
2. In regards to an HCl molecule, does this also mean that the partially positive H can attract negative ions and the partially negative Cl can attract positive ions from another compound such as KCl?
It can attract negative ions - which is why HCl is a strong acid and reacts with a lot of salts. Like
HCl+F-=HF+Cl-
Partially negative Cl can attract positive ions from another compound. Actually not KCl, specifically, because K+ has a closed electron shell. On the other hand, partially negative Cl readily attracts positive ions from compounds like AlCl3.
 
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1. What is a polar covalent bond?

A polar covalent bond is a type of chemical bond where two atoms share electrons unequally, resulting in a slight positive and negative charge on each atom.

2. How does a polar covalent bond differ from a nonpolar covalent bond?

In a nonpolar covalent bond, the electrons are shared equally between the two atoms, resulting in no separation of charge. In a polar covalent bond, the electrons are shared unequally, creating a dipole moment.

3. Why is HCl considered a polar covalent bond?

HCl is considered a polar covalent bond because the electronegativity difference between hydrogen and chlorine is large enough (3.0-2.1=0.9) to result in unequal sharing of electrons, creating a dipole moment.

4. How does the polarity of HCl affect its physical properties?

The polarity of HCl affects its physical properties in several ways. It has a lower boiling point and melting point compared to nonpolar molecules of similar size, due to the attraction between the slightly positive and negative ends of the molecule. It is also highly soluble in polar solvents, but not in nonpolar solvents.

5. Can a polar covalent bond be broken?

Yes, a polar covalent bond can be broken through a chemical reaction. The unequal sharing of electrons makes the bond relatively weak, allowing it to be easily broken and reformed with other atoms.

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