Chromatography interactive worksheet - Free Printable

Problem Analysis:

The question involves interpreting the results of a paper chromatography experiment to determine which colored dyes are present in a mixture (dye X). The image provided shows the separation of different colored dyes on a chromatography paper. Let's solve each part step by step.

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Part (a): Explain why the line is drawn in pencil and not in ink.

#### Solution:
In paper chromatography, the starting point for the dye samples is marked with a pencil line near the bottom of the paper. This line is used to place the samples of the dyes before running the experiment. The reason for using pencil instead of ink is:

- Pencil marks are non-volatile and do not dissolve in the solvent: If an ink pen were used, the ink could potentially dissolve in the solvent as it travels up the paper, contaminating the chromatogram and affecting the results.
- Pencil graphite does not interfere with the separation process: Pencil marks are inert and do not react with the dyes or the solvent, ensuring that only the dyes being analyzed are separated.

Thus, the use of pencil ensures that the starting point is clearly marked without introducing any additional substances that could interfere with the experiment.

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Part (b): Which colors are present in dye X?

#### Solution:
To determine which colors are present in dye X, we need to compare the positions of the spots on the chromatogram for dye X with those of the individual colored dyes (red, blue, yellow, brown, green).

1. Identify the spots for each color:
- Red: One spot is visible.
- Blue: One spot is visible.
- Yellow: One spot is visible.
- Brown: One spot is visible.
- Green: One spot is visible.
- Dye X: Multiple spots are visible.

2. Compare the positions of the spots in dye X with the individual colors:
- The spots in dye X match the positions of the spots for red, blue, yellow, and brown.
- There is no spot in dye X that matches the position of the green spot.

3. Conclusion:
The colors present in dye X are red, blue, yellow, and brown.

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Part (c): Which colored dye contains a substance not present in any of the other colored dyes?

#### Solution:
To determine which colored dye contains a substance not present in any of the other colored dyes, we need to analyze the unique spots on the chromatogram:

1. Analyze each dye:
- Red: Has one unique spot.
- Blue: Has one unique spot.
- Yellow: Has one unique spot.
- Brown: Has one unique spot.
- Green: Has one unique spot.
- Dye X: Contains spots corresponding to red, blue, yellow, and brown.

2. Identify the unique spot:
- The green dye has a spot that does not overlap with any of the spots in dye X or the other individual dyes. This indicates that the green dye contains a substance not present in any of the other dyes.

3. Conclusion:
The colored dye that contains a substance not present in any of the other colored dyes is green.

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Final Answers:

(a) The line is drawn in pencil because pencil marks are non-volatile and do not dissolve in the solvent, ensuring they do not interfere with the separation process.

(b) The colors present in dye X are red, blue, yellow, and brown.

(c) The colored dye that contains a substance not present in any of the other colored dyes is green.

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Boxed Final Answers:

\[
\boxed{
\begin{array}{l}
\text{(a) Pencil marks are non-volatile and do not dissolve in the solvent.} \\
\text{(b) Red, blue, yellow, and brown} \\
\text{(c) Green}
\end{array}
}
\]