Induced dipole-dipole
Weak intermolecular forces that exist between all molecules.
State what induced dipole-dipole forces are.
Act between the permanent dipole in different polar molecules.
State what permanent dipole-dipoles are.
A special type of permanent dipole-dipole interaction that occurs between a lone pair of electrons on a O, F or N and a H.
State what Hydrogen bond is.
Induced dipole-dipole forces.
What is term dispersion used for?
1-10 KJmol-1
State the strength of the induced dipole-dipole force.
There are no mobile charged particles in KBr therefore it will not be able to conduct electricity
Predict and explain the electrical conductivity of KBr.
It is less dense when frozen and has a relatively high melting and boiling point.
State two anomalous properties of water.
Van Der Waals forces
What is another name for London-London forces?
Increases as you go down the group.
Describe the trend in boiling points of the Noble gases as you go down the group.
I2 is a simple molecular substance and so forms a simple molecular lattice. The molecules are held in place by weak intermolecular forces which are weak and therefore need small amounts of energy to break. Therefore the boiling point will be low.
Predict and explain in terms of bonding the boiling point of I2.
Hydrogen bonds hold water molecules apart in an open lattice structure. the water molecules are further apart than water so it is less dense.
Explain why water is less dense when frozen.
Ethanol contains bother polar and non-polar parts so can dissolve in both water and hexane.
Predict the solubility of ethanol in water and hexane.
As the number of electrons in each molecule increases the larger the induced dipoles created and therefore more energy is required to overcome these forces.
State and explain what impacts the strength of the induced dipole-dipole interactions between molecules.
Fluorine molecules are non-polar and only have London forces between molecules. Hydrogen chloride molecules are are polar and have London forces and permanent dipole-dipole interactions between molecules. Extra energy if needed to break the additional permanent dipole-dipole interactions between hydrogen chloride molecules making the boiling point higher.
State and explain which molecule would have the highest boiling point.
Hydrogen bonds are extra forces, over and above London forces. More energy is required to break these forces, therefore the melting point is higher than expected from just London forces.
Explain why water has a higher melting point that expected.
In DNA hydrogen bonds exist between the A and T and C and G.
Identify a biological example of where Hydrogen Bonding is found.
Propane is a straight chain so is able to fit together more closely, therefore forming more London forces between the chains. The more London forces there are the higher the boiling point will be as more energy is required to break the bonds.
CCl4 is non-polar and therefore will form intermolecular forces with the hexane. Interactions weaken the intermolecular forces in the simple molecular lattice. The intermolecular forces break and the compound dissolves.
Predict and explain the solubility of CCl4 in hexane.
Relatively high surface tension and viscosity.
State another anomalous property that water has
The boiling point of hydrogen fluoride is much higher than that of other hydrogen halides, due to fluorine’s high electronegativity. The means that hydrogen bonding between molecules of hydrogen fluoride is much stronger than the permanent dipole–dipole forces between molecules of other hydrogen halides. More energy is therefore required to separate the molecules of hydrogen fluoride.
Predict and explain the boiling pint of hydrogen fluoride.