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Chemistry: Post your doubts here!

angelicsuccubus

angelicsuccubus

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Casablanca said:
Okay, this is pretty simple, but it's not stated clearly in my book, so I'll ask here.

Can someone please name the kinds of intermolecular forces in order of strength? I know that Hydrogen bonds are strong, and Van der Waals are weak, but just need confirmation. Also, are dipole-dipole forces and Ionic bonds the same thing?
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3 types of forces:
Strongest --1.Hydrogen Bonding

2.Dipole-dipole forces (polar molecules have permanent dipole-dipole forces so for example the force between a HCl molecule and another HCl molecule is a dipole-dipole dorce- the permanently positive end of a molecule is attracted to the permanently negative end of the other molecule)

Weekest --- 3.Instantaneous dipole-induced dipole forces (Van der Waal's forces)
 
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ibadsiddiqi

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angelicsuccubus said:
3 types of forces:
Strongest --1.Hydrogen Bonding

2.Dipole-dipole forces (polar molecules have permanent dipole-dipole forces so for example the force between a HCl molecule and another HCl molecule is a dipole-dipole dorce- the permanently positive end of a molecule is attracted to the permanently negative end of the other molecule)

Weekest --- 3.Instantaneous dipole-induced dipole forces (Van der Waal's forces)
Click to expand...
2 and 3 both are Van der Waals forces.;)
 
Casablanca

Casablanca

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ibadsiddiqi said:
sure..in increasing order of strength: Temporary dipole-dipole interactions(more commonly known as the dispersion forces), dipole-dipole interaction and the strongest hydrogen bonding.
No dipole-dipole forces are 1 of the van der waals forces, completely different thatn Ionic bonds. You want me to explain dipole-dipole interactions?
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Yes please, if it's not too much trouble. :)
 
angelicsuccubus

angelicsuccubus

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Casablanca said:
Err... Isn't that an ionic bond?

Now I'm even MORE confused. D:
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No I explained that as a permanent dipole-permanent dipole force. It's intermolecular .. between one HCl molecule and another HCl molecule and that's what I believe it is. But then ibadsiddiqi said that's the same as a van der waal's force so I put that up to ask him if he's calling the force induced between two HCl molecules a van der waal's force.
 
Casablanca

Casablanca

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Oh yeah, and, can someone briefly explain bond angles to me? Or link me to somewhere that explains it?

I get the main idea, that the more lone pairs there are, the more repulsion there is, but in which case is it 104.5 or 109? How can I tell what the bond angles in a compound would be?

Like, I have a question here that asks: Suggest the size of the C-O-C bond angle in methoxymethane (CH3OCH3). The answer is 104.5, but how would I figure that out? Why not 109?
 
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prannoy

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Casablanca said:
Okay, this is pretty simple, but it's not stated clearly in my book, so I'll ask here.

Can someone please name the kinds of intermolecular forces in order of strength? I know that Hydrogen bonds are strong, and Van der Waals are weak, but just need confirmation. Also, are dipole-dipole forces and Ionic bonds the same thing?
Click to expand...

No permanent dipoles are not ionic bonding as they also have the tendency to share Due to polarization. Hydrogen bonds are stronger than van der waals but not than ionic and covalent.
 
angelicsuccubus

angelicsuccubus

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Casablanca said:
Oh yeah, and, can someone briefly explain bond angles to me? Or link me to somewhere that explains it?

I get the main idea, that the more lone pairs there are, the more repulsion there is, but in which case is it 104.5 or 109? How can I tell what the bond angles in a compound would be?

Like, I have a question here that asks: Suggest the size of the C-O-C bond angle in methoxymethane (CH3OCH3). The answer is 104.5, but how would I figure that out? Why not 109?
Click to expand...
there must have been an indication that the molecule had a similar shape to water.. .14.5 is the bond angle in H2O, 107 in ammonia and 109.5 is for a tetrahedral molecule (where there are for pairs of electrons).
 
smzimran

smzimran

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Casablanca said:
Oh yeah, and, can someone briefly explain bond angles to me? Or link me to somewhere that explains it?

I get the main idea, that the more lone pairs there are, the more repulsion there is, but in which case is it 104.5 or 109? How can I tell what the bond angles in a compound would be?

Like, I have a question here that asks: Suggest the size of the C-O-C bond angle in methoxymethane (CH3OCH3). The answer is 104.5, but how would I figure that out? Why not 109?
Click to expand...
http://www.chemguide.co.uk/atoms/bonding/shapes.html#top

Its because central oxygen has two lone pairs as well
 
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ibadsiddiqi

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angelicsuccubus said:
No I explained that as a permanent dipole-permanent dipole force. It's intermolecular .. between one HCl molecule and another HCl molecule and that's what I believe it is. But then ibadsiddiqi said that's the same as a van der waal's force so I put that up to ask him if he's calling the force induced between two HCl molecules a van der waal's force.
Click to expand...
Yea thats permanent dipole dipole interaction but what i meant was that Van der Waal's forces comprise of 2 types of forces. One is dipole dipole interactions and the other is dispersion forces(aka temporary induced dipoles or London forces);)
 
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