separating techniques

Question 1

how do you conduct an investigation with chromatography?

Answer 1

1. draw a pencil line near bottom of paper
2. puts dots of dye of same size on line evenly spaced out - let dry
3. place paper in beaker with a small amount of solvent - BELOW PENCIL LINE
4. put lid on beaker - stops evaporation of solvent
5. remove paper once solvent is about 1cm from top - solvent front
6. leave paper to dry so solvent evaporates

Question 2

what does it mean if an Rf value is big?

Answer 2

dye is very soluble in solvent

Question 3

what is an Rf value

Answer 3

the ratio of the solute’s distance travelled to the solvent’s distance travelled

Question 4

what can fractional distillation be used to separate?

Answer 4

mixture of liquids - e.g. ethanol and water

Question 5

how does fractional distillation work

Answer 5

separating liquids by taking taking advantage of their different boiling points

Question 6

what can simple distillation be used to separate

Answer 6

components of a solution - e.g. sodium chloride solution

Question 7

what can crystallisation be used to separate?

Answer 7

solute from a solvent

Question 8

what can filtration be used to separate

Answer 8

solid from a liquid

Question 9

how can we tell if a substance is pure

Answer 9

melts + boils at fixed temp

Question 10

how can we tell if a substance is a mixture

Answer 10

melts or boils over a RANGE of temps

Question 11

how to calculate an Rf value

Answer 11

distance travelled by the component divided by the distance travelled by the solvent