chromatography (Required Practical) Flashcards
what is the steps to carry out the chromatography practical
- Use a ruler to draw a horizontal pencil line on the chromatography paper.
- The line should be around 2 cm from the bottom of the paper.
- Mark five pencil spots at equal spaces across the line.
- leave 1cm clear at each side
- Use a capillary tube to put a small spot of each of the known food colors and the unknown color onto the pencil spots.
- pour water into the beaker till 1cm depth (water is the solvent)
- attach the paper to a glass rod using tape and lower the paper into the beaker (the bottom of the paper should dip into the water)
- when the spots start to move make sure that you don’t touch the beaker
- remove the paper when the water moves 3/4 up the paper
- use a pencil to mark where the water reached
- then hang it to dry
what is a capillary tube
A capillary tube is simply a very thin glass tube.
how can you prevent the colors form spreading to each other
keep the spots relatively small
what are some things that you should do to the paper (2 things) ( 1 for the beaker)
make sure that the pencil line with the spots of ink must be above the surface of the water and will wash the ink of the line
make sure the sides of the paper do not touch the sides of the beaker so it will not interfere with the way the water moves
put a lid on the beaker to reduce evaporation of the solvent
what does it mean when a color has 3 different spots
there are 3 different colors
what does it mean when the spots line up with other spots
it meas that they both have the same mixture of color in them
how can you identify the chemicals in the colours
rf values
how can you calculate the rf values
- Measure the distance from the pencil line to the center of each spot.
- We then measure the distance moved by the water from the pencil line.
3.RF value = distance moved by chemical
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distance moved by solvent
