Question 1: A pure substance contains only one type of particle, such as atoms, molecules, or compounds. It has a fixed composition and distinct properties. Mixtures, on the other hand, are combinations of different substances that can be separated.

Answer: A pure substance has only one type of particle and a fixed composition; mixtures contain different substances and can be separated.

Question 1: What is the main difference between a pure substance and a mixture?

Answer: A pure substance contains only one type of particle, while a mixture contains two or more substances that can be separated.

Question 2: Name two methods used to test the purity of a substance.

Answer: Melting point analysis and chromatography.

Question 1: A sample of salt (NaCl) weighs 10 grams and is found to contain 9.5 grams of pure NaCl. Calculate the percentage purity of the sample.

Answer: Percentage purity = (Mass of pure substance / Total mass of sample) × 100 = (9.5 g / 10 g) × 100 = 95%

Question 2: A solution contains 50 grams of a pure substance dissolved in 250 milliliters of water. Calculate the concentration in grams per liter (g/L).

Answer: Concentration = (Mass of solute / Volume of solution in liters) = 50 g / 0.25 L = 200 g/L

Question 1: Describe a basic laboratory procedure to test whether a sample of water is pure using boiling point analysis.

Answer: Heat the water sample and note the boiling point. Pure water boils at 100°C at standard pressure. Deviations indicate impurities.

Question 2: List three safety precautions that must be followed when performing purity tests in the lab.

Answer: Wear safety goggles, handle chemicals with care, and work in a well-ventilated area.

Question 1: A sample of copper sulfate shows a melting point of 110°C, while the pure substance melts at 110°C. The sample's melting point range is wider than standard. What does this suggest about the sample's purity?

Answer: The wider melting point range suggests the sample is impure, as impurities lower and broaden the melting point.

Question 1: Explain how chromatography can be used to determine the purity of a chemical sample. Include the basic principle and steps involved.

Answer: Chromatography separates components of a mixture based on their movement through a medium. A pure substance will produce a single spot, while impurities will result in multiple spots. The sample is applied to a stationary phase, and a solvent moves through it, carrying different components at different rates, allowing analysis of purity.

Question 2: Discuss the importance of analyzing purity in the pharmaceutical industry and the consequences of using impure medicines.

Answer: Purity analysis ensures medicines contain only the active ingredients without harmful impurities, guaranteeing safety and efficacy. Using impure medicines can lead to ineffective treatment, adverse reactions, or toxicity, posing serious health risks.