Question

On a thin layer chromatographic plate, an organic compound moved by 3.5 cm, while the solvent moved by 5 cm. The retardation factor of the organic compound is \( \_\_\_\_ \times 10^{-1} \).

Answer 1

Correct Answer: 7

This problem requires determining the retardation factor (Rf) for an organic compound using measurements of its migration distance and the solvent front's migration distance on a thin layer chromatography (TLC) plate. The result must adhere to a specific formatting convention.

Concept Used:

In thin layer chromatography (TLC), the retardation factor, denoted as \( R_f \), is a dimensionless ratio representing the distance a compound travels relative to the distance the solvent front travels. This factor is intrinsic to a compound under defined stationary and mobile phase conditions. The formula for calculating the retardation factor is:

\[R_f = \frac{\text{Distance travelled by the compound (solute)}}{\text{Distance travelled by the solvent front}}\]

The \( R_f \) value ranges from 0 to 1, as a compound cannot migrate beyond the solvent front.

Step-by-Step Solution:

Step 1: Extract the provided measurements.

The distance migrated by the organic compound (solute) is 3.5 cm.

The distance migrated by the solvent (mobile phase) is 5 cm.

Step 2: Apply the retardation factor formula with the obtained values.

\[R_f = \frac{\text{Distance travelled by the compound}}{\text{Distance travelled by the solvent front}} = \frac{3.5 \text{ cm}}{5.0 \text{ cm}}\]

Step 3: Compute the numerical value of the retardation factor.

\[R_f = \frac{3.5}{5.0} = 0.7\]

Step 4: Format the calculated \( R_f \) value as \( \_\_\_\_ \times 10^{-1} \).

To express 0.7 in the required format, we rewrite it as:

\[0.7 = 7 \times 0.1\]

Recognizing that \( 0.1 \) is equivalent to \( 10^{-1} \), we get:

\[R_f = 7 \times 10^{-1}\]

Final Computation & Result:

The retardation factor is computed by dividing the distance traveled by the compound by the distance traveled by the solvent.

\[R_f = \frac{3.5}{5.0} = 0.7\]

Expressing this result in the specified format:

\[0.7 = 7 \times 10^{-1}\]

Therefore, the retardation factor for the organic compound is 7 \( \times 10^{-1} \).