Question 1: Define chromatography and explain its purpose in chemical analysis.

Answer: Chromatography is a technique used to separate mixtures into their individual components based on differences in how substances distribute themselves between a stationary phase and a mobile phase, helping to identify and analyze substances' purity.

Question 2: Describe the basic mechanism by which chromatography separates different substances in a mixture.

Answer: Chromatography separates substances based on their different affinities to the stationary phase and their solubility in the mobile phase, causing them to move at different rates.

Question 1: Calculate the Rf value for a pigment that travels 3.5 cm on the chromatogram while the solvent front travels 10 cm. Show your formula and units.

Answer: Rf = distance traveled by substance / distance traveled by solvent front = 3.5 cm / 10 cm = 0.35

Question 2: A mixture of dyes is separated by chromatography. The blue dye travels 4.2 cm, and the solvent front is 9.0 cm. What is the Rf value? Round to two decimal places.

Answer: Rf = 4.2 cm / 9.0 cm = 0.47

Question 1: List three safety precautions that should be taken when performing chromatography in a laboratory setting.

Answer: Wear gloves and safety goggles, work in a well-ventilated area or fume hood, and handle solvents with care to avoid spills and inhalation.

Question 2: Identify two variables that can affect the separation quality in paper chromatography.

Answer: The type of solvent used and the temperature during the process.

Question 3: Explain why chromatography is useful in testing the purity of a sample.

Answer: Chromatography allows scientists to separate and identify individual components within a mixture, making it possible to detect impurities or verify the purity of a substance by analyzing the number, position, and intensity of the separated spots or peaks.

Question 1: A chromatogram shows three distinct spots for a sample, with Rf values of 0.25, 0.50, and 0.75. What does this indicate about the sample's composition?

Answer: It indicates the sample contains at least three different components, each with different affinities for the stationary and mobile phases, separated based on their Rf values.

Question 2: In an experiment, the same sample produced different Rf values in two different solvents. What could be the reason for this observation?

Answer: Different solvents have varying polarities and affinities, which affect how the substances travel, leading to different Rf values.

Question 3: A student notices that two spots on a chromatogram are very close to each other, with Rf values of 0.45 and 0.47. What might this suggest about the two substances?

Answer: The two substances are very similar in their properties and have similar affinities for the stationary and mobile phases, making their separation less distinct.

Question 1: How is chromatography used in the food industry to ensure product quality?

Answer: Chromatography is used to analyze food ingredients, detect contaminants, and verify the presence and concentration of additives or preservatives to ensure safety and compliance.

Question 2: Describe a way chromatography technology can assist in forensic science investigations.

Answer: Chromatography helps identify and analyze substances such as drugs, toxins, or residues from crime scenes, aiding in criminal investigations by providing evidence of substances present.