chromatography

Question 1

what is chromatograhy

Answer 1

separation of components from a mixture so they can be identified

there is a mobile and stationary phase

Question 2

what is thin layer chromatography and paper chromatography

Answer 2

mixtures spotted and dried on paper (paper chroma) or plate with silica gel (tlc)
the paper/plate is placed in solvent - below spotting
solvent goes up the paper/plate

Question 3

how do you calculate the Rf value

Answer 3

distance component moved/ distance solvent moved

Question 4

what are the advantages and disadvantages of chromatography

Answer 4

pros - cheap, easy, multiple at once

cons - long time, spot detection difficult

Question 5

what is the steric effect

Answer 5

separation based on molecule size using porous stationary phase

Question 6

what is gas chromatography

Answer 6

gas/liq gets injected into a heated column
the gas travels to the bottom
different molecules move at different rates
detector detects different molecules

Question 7

what is liquid chromatography

Answer 7

liquid pushed through a column - high pressure needed
different molecules travel at different speeds
detector detects when substances leave

Question 8

what is retention time

Answer 8

time taken from injection to emergence (tR)

some substances could have the same retention time under specific conditions

Question 9

what is retention volume

Answer 9

volume of the mobile phase

Vr = tR x flow rate

Question 10

what is the relative retention

Answer 10

α = tR/tR std

or Vr/Vr std

this varies with temperature
advantage - it doesnt rely depend on column length or flow rate