JEE Main · 2022 · 25 Jul 2022 · Shift 2 · Practical and Analytical Chemistry

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The separation of two coloured substances was done by paper chromatography. The distances travelled by solvent front, substance A and substance B from the base line are 3.25 cm, 2.08 cm and 1.05 cm respectively. The ratio of

R_{f}

values of A to B is ____

Answer: 2

Solution

The retention factor

R_{f}

is defined as:

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

For substance A:

R_{f_{A}} = \frac{2.08}{3.25}

For substance B:

R_{f_{B}} = \frac{1.05}{3.25}

Ratio:

\frac{R _{f_{A}}}{R _{f_{B}}} = \frac{2.08/3.25}{1.05/3.25} = \frac{2.08}{1.05} \approx 1.98 \approx 2

The answer is 2.

JEE Main · 2022 · 25 Jul 2022 · Shift 2 · Integer answer

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