This question is about paper chromatography. A food colouring contains a dye. Plan an investigation to determine the Rf value for the dye in this food colouring. Your plan should include the use of: • a beaker • a solvent • chromatography paper.- 6129

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1. I drew a straight line near the bottom of the chromatography paper using a pencil. I then added a small spot of food colouring onto the pencil line. Next, I poured some water (the solvent) into a beaker, making sure the level of the water was below the pencil line. I placed the chromatography paper into the beaker so the bottom was in the water, but the spot was not covered. I put a lid on the beaker and waited for the solvent to travel up the paper. Once it was near the top, I took the paper out, marked the solvent front, and left the paper to dry.
   I measured the distance from the pencil line to the centre of the spot and also from the pencil line to the solvent front. Then I used these measurements to calculate the Rf value.

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