JEE Main · 2021 · 25 Feb 2021 · Shift 1 · Practical and Analytical Chemistry

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Using the provided information in the following paper chromatogram:
Fig: Paper chromatography for compounds A and B. The calculated

R_{f}

value of A is _____

\times 1 0^{- 1}

Answer: 4

Solution

The retention factor compares how far the spot has moved with how far the solvent has moved, both measured from the base line:

R_{f} = \frac{distance moved by the substance}{distance moved by the solvent front}

The solvent front stands 5 cm above the base line, and the spot of A lies 2 cm above it, so

R_{f} (A) = \frac{2}{5} = 0.4

which is

4 \times 1 0^{- 1}

JEE Main · 2021 · 25 Feb 2021 · Shift 1 · Integer answer

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