JEE MAIN - Chemistry (2019 - 10th April Evening Slot - No. 17)
In chromatography, which of the following statements is incorrect for Rf ?
Rf value depends on the type of chromatography.
Higher Rf
value means higher adsorption.
Rf
value is dependent on the mobile phase.
The value of Rf
can not be more than one.
Explanation
Rf = $${x \over y}$$
$$x$$ = Distance moved by the substance from baseline
$$y$$ = Distance moved by the solvent from baseline
Option A : Correct. The Rf value can depend on the type of chromatography being used because different methods can use different stationary and mobile phases, which can influence how far a substance travels.
Option B : Incorrect. The Rf value is actually inversely related to adsorption. A higher Rf value indicates that the substance is less strongly adsorbed to the stationary phase, and therefore moves further along with the mobile phase.
Option C : Correct. The nature of the mobile phase can greatly influence the Rf value. The more compatible the substance is with the mobile phase, the further it will travel, leading to a higher Rf value.
Option D : Correct. By definition, the Rf value cannot exceed one, as a substance cannot travel further than the solvent.
So, Option B is incorrect for the Rf value in chromatography.
$$x$$ = Distance moved by the substance from baseline
$$y$$ = Distance moved by the solvent from baseline
Option A : Correct. The Rf value can depend on the type of chromatography being used because different methods can use different stationary and mobile phases, which can influence how far a substance travels.
Option B : Incorrect. The Rf value is actually inversely related to adsorption. A higher Rf value indicates that the substance is less strongly adsorbed to the stationary phase, and therefore moves further along with the mobile phase.
Option C : Correct. The nature of the mobile phase can greatly influence the Rf value. The more compatible the substance is with the mobile phase, the further it will travel, leading to a higher Rf value.
Option D : Correct. By definition, the Rf value cannot exceed one, as a substance cannot travel further than the solvent.
So, Option B is incorrect for the Rf value in chromatography.
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