Purity, formulations and chromatography

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Question 20
Medium

An analyst investigated a batch of orange food dye using paper chromatography.

a.

The orange dye formulation consists of 65%65\%65% yellow dye and 35%35\%35% red dye by mass. Determine the simplest whole-number ratio of yellow dye : red dye in this formulation.

[2]
b.

On the developed chromatogram, the analyst obtained the following measurements:

  • the distance travelled by the yellow dye = 10.5 cm10.5\text{ cm}10.5 cm
  • the distance travelled by the solvent front = 15.0 cm15.0\text{ cm}15.0 cm

Calculate the RfR_{\text{f}}Rf​ value of the yellow dye using the equation: Rf=distance moved by dyedistance moved by solventR_{\text{f}} = \frac{\text{distance moved by dye}}{\text{distance moved by solvent}}Rf​=distance moved by solventdistance moved by dye​

[2]
c.

Under identical experimental conditions, if the analyst tested a different formulation of orange dye containing 45%45\%45% yellow dye and 55%55\%55% red dye, state what would happen to the RfR_{\text{f}}Rf​ value of the yellow dye.

[1]

Purity, formulations and chromatography Questions

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