Given below are two statements: Statement I : Retardation factor $(\mathrm{R}_{\mathrm{f}})$ can be measured in meter / centimeter. Statement II: $\mathrm{R}_{\mathrm{f}}$ value of a compound remains constant in all solvents. Chose the most appropriate answer from the options given below:

(B) Both statement I and statement II are false

(A) Statement I is true but statement II is false

(C) Both statement I and statement II are true

(D) Statement I is false but statement II is true

JEE Main · 2021 · 17 Mar 2021 · Shift 1 · Practical and Analytical Chemistry

Given below are two statements:
Statement I : Retardation factor

(R_{f})

can be measured in meter / centimeter.
Statement II:

R_{f}

value of a compound remains constant in all solvents.
Chose the most appropriate answer from the options given below:

(A)Statement I is true but statement II is false
(B)Both statement I and statement II are false✓ Correct
(C)Both statement I and statement II are true
(D)Statement I is false but statement II is true

Answer: (B)

Solution

The retardation factor is the distance travelled by the spot divided by the distance travelled by the solvent front. Being a ratio of two lengths it is a pure number and carries no unit, so it cannot be quoted in metres or centimetres. Its size is fixed by how the compound distributes itself between the stationary phase and the mobile phase, so a change of solvent changes it, which is why an

R_{f}

is always reported together with the solvent system used. Both Statement I and Statement II are false.

JEE Main · 2021 · 17 Mar 2021 · Shift 1 · Single correct option

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JEE Main · 2021 · 17 Mar 2021 · Shift 1 · Practical and Analytical Chemistry

Solution

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