Molecular Forces

Question 1

what is a INTRA molecular force

Answer 1

the forces that holds atoms togethers within a molecule

Question 2

what is a INTER molecular force

Answer 2

the forces that exist between molecules (covalent molecules) and are weaker than intra

Question 3

order the intermolecular forces from strongest to weakest

Answer 3

1. Hydrogen Bonding
2. Dipole - Dipole
3. Dispersion forces

Question 4

when does hydrogen bonding occur

Answer 4

when there is an IMF between the lone pairs of electrons on O, N or F and the hydrogen that is attracted to it becomes partial pos

Question 5

when does dipole dipole occur

Answer 5

when the partial positive of a polar molecule interacts with the partial negative of a neighbouring polar molecule

Question 6

When do dispersion forces occur

Answer 6

when the electrons of non polar/neutral molecules are for a second concentrated on one side due to a momentary shift creating a temporary dipole which induces dipoles in neighbouring molecules and so on

Question 7

between with molecules do dispersion forces occur

Answer 7

IN ALL MOLECULES (POLAR AND NON POLAR)

Question 8

what is an example of each type of IMF

Answer 8

hydrogen bonding - H2O
dipole dipole - HCl
dispersion - F2

Question 9

what 4 factors determine the strength of IMFs and therefore melt boil point

Answer 9

1. type of IMF
2. size of molecule - all molecules have disp force which rely on number of electrons therefore size
3. polarity
4. shape - more surface area increase melt point

Question 10

explain the melt/boil point of each type of IMF

Answer 10

dispersion - weak non polar bonds = low melt
DD - more polar more strength = high melt
Hydrogen - strong bonds - highest melt boil

Question 11

what is vapour pressure and what does it measure

Answer 11

the pressure of a gas colliding with the wall above it’s liquid state in a closed container after it evaps (measure of tendency to evap)

Question 12

the higher a substances VP =

Answer 12

the easier and faster it is to evaporate and the weaker it’s IMFs

Question 13

higher temp =

Answer 13

higher VP = weaker IMF

Question 14

what is the rule of solubility

Answer 14

generally substances (which use similar types of IMFs) will be soluble with one another

Question 15

what are 2 examples of this solubility rule

Answer 15

petrol (non polar) is INSOLUBLE in water (polar)

sugar (polar) in water (polar)