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CIE iGCSE Co-Ordinated Science C12.3 Chromatography Exam Style Questions Paper 2

CIE iGCSE Co-Ordinated Science Paper 2 - All Chapters

Question

The chromatogram for substances P, Q, R and S is shown.

Which statement is correct?

A. P and R are both pure substances.
B. P has a higher \(R_f\) value than Q.
C. R is a mixture of P and Q.
D. S is a mixture of Q and one other substance.

▶️ Answer/Explanation
S shows two spots at different positions, indicating it is a mixture of two substances. One spot matches Q’s position, confirming it contains Q and one other component. P and R show single spots (pure).
✅ Answer: (D)

Question

The chromatogram of four different inks is shown.

Which ink has an \(R_f\) value of 0.53?

▶️ Answer/Explanation
\(R_f = \frac{\text{distance travelled by substance}}{\text{distance travelled by solvent}}\). From the chromatogram, if the solvent front moved 10 cm, then a spot at 5.3 cm would have \(R_f = 0.53\). Ink 2 is at this position. Ink 1 would be 0.38, ink 3 about 0.46, and ink 4 about 0.69.
✅ Answer: (B)

Question

The chromatogram of four substances is shown.

Which substance has an \(R_{\mathrm{f}}\) value of 0.25?

▶️ Answer/Explanation
\(R_f = \frac{\text{distance moved by substance}}{\text{distance moved by solvent}}\). The spot that has travelled one-quarter of the solvent front distance corresponds to \(R_f = 0.25\), which is substance B on the chromatogram.
✅ Answer: (B)

Question

The boiling points of three substances, W, X and Y, are shown.

The substances are tested using chromatography.

The chromatogram is shown.

Which statement is correct?

A. One of the components of Y has a boiling point of 132 °C.
B. Substance Y has a smaller boiling point range than substance W.
C. Substance W produces the largest Rf value.
D. Substance X is an impure mixture.

▶️ Answer/Explanation
Substance X has a single sharp boiling point (132 °C) and shows a single spot on the chromatogram, indicating it is a pure substance. Substance Y has a boiling point range (141–145 °C) and shows multiple spots, confirming it is a mixture. Since Y is a mixture, one of its components could have a boiling point of 132 °C. Substance W has a range (116–118 °C), making it impure. The Rf value depends on the chromatogram, which is not provided in detail here.
✅ Answer: (A)

Question

Dye X is a mixture of different coloured substances.

Chromatography is used to compare X with three other mixtures, P, Q and R. The results are shown.

Which mixtures contain dye X?

A. P, Q and R
B. P and Q only
C. P only
D. R only

▶️ Answer/Explanation
A mixture contains dye X only if every spot from X appears at the same height (same \(R_f\) value) in that mixture’s chromatogram track.
Comparing the spot patterns, only mixture P shows spots matching all of X’s spots at the identical positions.
Mixtures Q and R are missing at least one matching spot, so they do not contain dye X.
✅ Answer: (C)
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