CAIE IGCSE Chemistry 12.3.4 And Use the Equation for Rf Rf Questions

Work through real CAIE IGCSE Chemistry questions to apply the R_f equation, compare spots and interpret solvent-front distances.

Exam points

state the R_f equation as distance travelled by the substance divided by distance travelled by the solvent front
calculate R_f values from chromatogram distances and select the matching answer
use R_f values, which are normally less than 1, to compare and identify substances
interpret how solubility and travel distance affect R_f values and use the equation to identify spots or solvent-front measurements

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$39 R_{\mathrm{f}}$ values are used to identify unknown substances using paper chromatography.
Which statements about $R_{\mathrm{f}}$ values are correct?
$1 \quad R_{\mathrm{f}}$ values are always less than 1.0.
$2 \quad R_{\mathrm{f}}$ value = distance travelled by solvent ÷ distance travelled by unknown substance.
3 The higher the $R_{\mathrm{f}}$ value, the further the unknown substance travels.
$4 R_{\mathrm{f}}$ values are not affected by the solubility of the unknown substance.

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CAIE IGCSE Chemistry 12.3.4 And Use the Equation for Rf Rf Questions question 1