[Jenny3687]

Water's strongest intermolecular force would be hydrogen bonding, and methanol's strongest intermolecular forces is also hydrogen bonding.

I know hydrogen bonding is the strongest type of intermolecular forces, and I know it occurs when a hydrogen is bonded to an oxygen, nitrogen or fluoring atom and there is also a lone pair on that atom.

When a mixture is composed of water and methanol, do the intermolecular forces work together, and therefore make a very strong force? Or do the forces cancel each other out, and form weak bonds?

My guess is that the water and methanol are going to hydrogen bond together, and therefore form a very strong molecule, with high polarity. Is this correct?

Thank you!

[Donaldson Tan]

My guess is that the water and methanol are going to hydrogen bond together, and therefore form a very strong molecule, with high polarity. Is this correct?

You make it sound as if intermolecular bonding is equivalent to a covalent bond.

[Jenny3687]

I'm confused as to what you mean.

I'm assuming the water and methanol will bond together, and form a new molecule.

I know the difference between intermolecular bonding and covalent bonding, I dont see how I'm making it sound as if they are equivalent...?

[Donaldson Tan]

I'm assuming the water and methanol will bond together, and form a new molecule.

Intermolecular bonding do not produce a new molecule.

[Mitch]

Hydrogen bonding is not an actual covalent bond!

[Jenny3687]

The water and methanol will bind together. not intermolecularly. intermolecular forces occur within a molecule. covalent bonding occurs with other atoms/molecules.

grrr nevermind, this is too confusing.

i wasnt looking for an explanation between intermolecular and covalent bonds.

[Borek]

intermolecular forces occur within a molecule

Intramolecular forces occur within a molecule, intermolecular forces are between molecules.

Unless my English fails me.

[Jenny3687]

wow, that confused me even more! lol

i think i most likely made a typo.

borek, u are correct. I meant intErmolecular forces as in those forces between molecules. i appologize!

[Jenny3687]

I confused myself as to what I was even asking, so I'm trying to rephrase my original question..



I don't understand how water and methanol will bond, if at all. If there is a mixture of 50:50 methanol water, what bonding takes place between the water and methanol?

Both molecules (water and methanol) are covalently bonded, and polar. They both will exhibit hydrogen bonding becuase of the O-H bond in their molecular structure, and they will both exhibit dipolar forces.

In this case, methanol is added to the water, and the water acts as a solvent.

I know the methanol water mixture has a greater polarity than just water by itself and methanol by itself.

Can someone help me understand why the polarity of the mixture is stronger?

I hope that cleared it up a bit, and thanks for helping me by making me think it through by myself! That's the best kind of help, and the only true way one can learn!

[Mitch]

I don't understand how water and methanol will bond

Water and methanol will not bond! There is only a slight attraction for one an other, not a bond.

[gregpawin]

I like your use of exclaimation points mitch.

[Jenny3687]

Nevermind.

what's the point of this website anyway? I come here for help and get treated like an idiot...

so there is an attraction due to their polarities. i get it. thanks for nothing.

grrr

[mike]

Water and methanol are miscible so you can mix them together completely.

You are right they probably can form some hydrogen bonds with each other. If you mixed your 50:50 water and methanol there would still be a lot of water-water interactions and methanol-methanol interactions as well as your water-methanol interactions.

I am not sure why the mixture would be more polar than either of the components though. If anything I would say that by adding the methanol to the water you would disrupt the hydrogen bonding a little so there would be weaker interactions.

What do you think?

[plu]

Hi Jenny,

I believe we are having some difficulties here with definitions of terms.  Intramolecular bonds are bonds within a molecule.  These bonds keep the atoms of a molecule together.  Covalent bonds and ionic bonds are types of intramolecular bonding.  Intermolecular bonds are bonds between molecules.  These are the bonds that affect the degree of attraction the molecules in a substance have for each other and thus affect the physical properties of the substance (such a melting point, boiling point, and vapour pressure).  Hydrogen bonding, dipole-dipole bonding, and London dispersion forces are types of intermolecular bonding.  Intermolecular bonding however does not lead to the formation of new molecules.  Intermolecular bonds simply keep molecules attracted to one another within a substance or mixture.  You are absolutely right in saying that hydrogen bonding is the most important form of intermolecular bonding in a mixture of ethanol and water.  However, hydrogen bonding will not cause ethanol and water to form a new molecule.  It will only keep the molecules of the mixture together (i.e. not fly off as a gas).  I hope this helps

plu

[pantone159]

When a mixture is composed of water and methanol, do the intermolecular forces work together, and therefore make a very strong force? Or do the forces cancel each other out, and form weak bonds?

My guess is that the water and methanol are going to hydrogen bond together, and therefore form a very strong molecule, with high polarity. Is this correct?

Hydrogen bonds are much weaker than the covalent bonds that hold together the atoms of a single molecule.  They don't join two different molecules into one big one.  They aren't strong enough, and the molecules that are attracted together don't stay stuck permanently.  I.e., in a single water molecule, the oxygen atom keeps the same hydrogen atoms connected to it.  (More or less, anyways).  But when two water molecules hydrogen bond, the two don't stay stuck permanently.  The two will attract each other, but then something will come along and knock one of the water molecules away, then the remaining molecule might hydrogen bond to another molecule.  So there is attraction, but not to the point of making a double-sized molecule.

In a water and methanol mixture, each will hydrogen bond to its own kind and also the other.  I would think that the polarity of the mixture would be somewhere between the polarity of pure water and of pure methanol.