Chapt. 5

Question 1

solvent

Answer 1

particles moving at random

Question 2

solute

Answer 2

particles in lattice

Question 3

solution

Answer 3

forces b/w solute particles have been overcome
the forces b/w some solvent molecules have been overcome
new forces are present b/w solvent and some solute particles

Question 4

water as a solvent

Answer 4

1. polar covalent compounds that can form hydrogen bonds with water
   - the larger the non polar part = less soluble
   eg. ethanol
   2.polar covalent compound that ionise in water
   - some covalent molecules are so polar they break when placed in water
   eg. HCl
2. dissociation of soluble ionic compound
   - an ion-dipole attraction is where the H20 molecules surround the ions making them hydrates

Question 5

chromatography

Answer 5

involves the separation of components in a mixture
- involves a stationary and mobile phase
- separation occurs b/c different components will move over the stationary phase at different rates

Question 6

adsorption

Answer 6

occurs when a substance forms a bond with a surface

Question 7

desorption

Answer 7

breaking of the bond (dissolving back into the mobile phase)

Question 8

the rate of movement depends on

Answer 8

• how strongly the component absorbs onto the stationary phase
  how readily it desorbs in the mobile phase
• components that more strongly attracted to the stationary phase will take longer to reach the end of the stationary phase.
  the components most strongly adsorbed onto the stationary phase moves the shortest distance and so has a lower RF

Question 9

pros and cons of paper chromatography and thin layer chromatography

Answer 9

P.C
- cheap
- little preparation
l more efficient for polar and h2o soluble compounds
easy to handle and store
TLC
- detects smaller amounts
- better separation of less polar compounds
- corrosive materials can be used
wide rand of stationary phases are available

Question 10

thin layer chromatography (TLC

Answer 10

SP = thin layer of powder on a piece of glass or plastic
MP = suitable solvent (polar or non-polar)
origin = small dot of mixture near the bottom
- qualitative analysis
Rf value = distance moved from origin/distance from origin by solvent