Question 1: Chromatography is a technique used to separate mixtures based on differences in how components distribute between a stationary phase and a mobile phase. It is widely used in analysing the purity of substances and identifying unknown compounds.

Answer: Chromatography separates components of a mixture based on their different affinities for stationary and mobile phases.

Question 2: Name three common types of chromatography used in chemical analysis.

Answer: Thin-layer chromatography (TLC), paper chromatography, gas chromatography (GC)

Question 1: Explain the role of the stationary phase and mobile phase in chromatography.

Answer: The stationary phase holds the sample components in place, while the mobile phase moves through the stationary phase, carrying different components at different speeds based on their affinities.

Question 2: Describe how the polarity of substances affects their movement during paper chromatography.

Answer: More polar substances tend to interact more with the polar stationary phase and move slower, whereas less polar substances move faster with the mobile phase.

Question 1: A pigment sample is spotted on a chromatography paper. The solvent front travels 15 cm, and a particular pigment travels 9 cm. Calculate the Rf value of the pigment. (Rf = distance moved by substance / distance moved by solvent front).

Answer: Rf = 9 cm / 15 cm = 0.6

Question 2: If a mixture contains two components with Rf values of 0.3 and 0.7, which component is more polar? Justify your answer.

Answer: The component with Rf 0.3 is more polar because it interacts more with the stationary phase and moves less.

Question 1: Describe the key safety precautions to take when performing paper chromatography in a laboratory setting.

Answer: Wear safety goggles and gloves, handle solvents in a well-ventilated area, and avoid inhaling fumes.

Question 2: In an experiment, the Rf values for three components were found to be 0.25, 0.55, and 0.75. Which component is likely the least polar? Explain your reasoning.

Answer: The component with Rf 0.75 is likely the least polar because it travels furthest with the mobile phase and interacts less with the stationary phase.

Question 1: A chromatogram of a drug sample shows multiple spots with different Rf values. What does this indicate about the sample's purity?

Answer: It indicates the sample is impure, containing multiple components or contaminants.

Question 2: Explain how chromatography is used in the food industry to detect additives or contaminants.

Answer: Chromatography separates and identifies additives, preservatives, and potential contaminants in food products, ensuring safety and compliance with regulations. It allows for rapid analysis of complex mixtures to verify ingredient purity and detect illegal substances.

Question 3: Discuss the advantages and limitations of using gas chromatography in analysing complex mixtures such as petroleum or environmental samples.

Answer: Gas chromatography offers high sensitivity, rapid analysis, and excellent separation of complex mixtures like petroleum. However, it requires volatile samples, expensive equipment, and skilled operation. It may not be suitable for non-volatile or thermally unstable compounds, limiting its use in some analyses.