[vhpk]

Why does the solubility of hidrocarbon decrease when the number of carbon of the molecular increase

[english]

Generally it's because C-H bonds are nonpolar, so as you increase the number of C-H bonds water cannot bring the species into solution very well.  Immiscibility results.

General rule (if I can remember correctly) is that alkanes with 4 or less carbons can be solubilized to a certain extent.  From there on up the number of C atoms makes it relatively difficult to bring the alkane into solution.


Use nonpolar solvents for larger alkanes.

[vhpk]

Explain why doesn't Clorine make hidrogen bond with water? From that, compare the solubility of: HF, HCl, HBr, HI

[xiankai]

the water molecule is polar; it has 2 partially positive hydrogen atoms and a partially negative oxygen atom with two lone pairs.

in order to make a hydrogen bond with it, you need a polar molecule, so that the partially positive end can H-bond with the lone pairs on the oxygen, while the partially negative end H-bonds with the hydrogen.

what do you think about chlorine?

[vhpk]

I've known about the mechanism of H-force, but the thing I concern is that, clorine is a strong un-metal, it only loses F and O, but it can't make H-bond with H₂O

[xiankai]

it has something to do with electronegativity, there's a hint

[vhpk]

I don't understand your hint very much because I don't understand the word"negativity" but do you mean that the electronegativity of Cl is 3,16 less than Oxygen is 3,44 so it can't make H-bond.
I hope I'm right

[english]

I don't understand your hint very much because I don't understand the word"negativity" but do you mean that the electronegativity of Cl is 3,16 less than Oxygen is 3,44 so it can't make H-bond.
I hope I'm right

OK.

If you follow the trend in atomic size, you would be able to estimate that Cl is larger than N. 

According to Linus Pauling and his Scale of Electronegativities, Cl and N both have an electronegativity of 3.0.


But Cl cannot form hydrogen bonds? 

Well it turns out that the greater polarizability, due to resulting larger size of the Cl atom, means that hydrogen bonding is not as effective with Cl as it is with N.

Polarizability means that the atom's electron cloud is more easily distorted because its valence electrons, or outer electrons, are held more loosely.  Think about what happens when you have a weak magnet, and are trying to use it to pick up a much heavier object.  You have a "loose" force because of a weak magnetic field (I don't know if loose force is a good phrase here, bear with me ).  In this case a weak nuclear charge gives a "loose" electron cloud.


For O and F, on the other hand, well they can form hydrogen bonds because they are the two most electronegative elements.

A hydrogen bond is not a full bond, which is weaker than a covalent bond but stronger than a London force (van der Waals forces), . 

H — O - - - - - H — O — H
        |
        H                   
                       

[vhpk]

Next question, whether CH₃-O-CH₃ and aldelhit can make H-bond

[Yggdrasil]

To have a hydrogen bond, you must have a hydrogen bond donor and a hydrogen bond acceptor.  A hydrogen bond donor must have a hydrogen bonded to a F, O, or N.  A hydrogen bond acceptor must have a lone pair on a F, O, or N.  So, can dimethyl ether act as a hydrogen bond donor or acceptor?  What about an aldehyde?

[vhpk]

Well it turns out that the greater polarizability, due to resulting larger size of the Cl atom, means that hydrogen bonding is not as effective with Cl as it is with N.

But when N and Cl made their bond, they are ions, and the radial of N^3- is bigger than Cl^-, so whether we use the size of atom to explain

[english]

Well it turns out that the greater polarizability, due to resulting larger size of the Cl atom, means that hydrogen bonding is not as effective with Cl as it is with N.

But when N and Cl made their bond, they are ions, and the radial of N^3- is bigger than Cl^-, so whether we use the size of atom to explain

When you form an anion, you are filling up degenerate orbitals.  Electrons in the same subshell and energy level do not shield each other very effectively, and thus do not effect the atom's overall nuclear charge, Z_eff.  Chlorine still has one more set of core electrons than nitrogen, which shield it's outer electrons effectively, thus reducing the nuclear charge.

Polarizability doesn't necessarily increase with electron gain when you form an anion.


Iodine is the most polarizable natural element, yet its atom only forms an anion with a -1 charge.

[vhpk]

Organic acid and alcol, which has stronger H-bond

[english]

Organic acid and alcol, which has stronger H-bond

You have to be more specific and less confusing.  You mean alcohol?  That is an organic acid.

[vhpk]

, sorry I mean carboxylic acid like :CH₃COOH