Question 1: Define the term 'concentration' in the context of a solution.

Answer: Concentration is the amount of solute present in a given volume of solvent or solution, usually expressed in molarity (mol/dm³).

Question 2: Explain why knowing the concentration of a solution is important in chemical reactions.

Answer: Knowing the concentration helps determine the amount of reactants needed for reactions, ensures safety, and allows for accurate and reproducible results.

Question 1: Calculate the molarity of a sodium chloride (NaCl) solution prepared by dissolving 5 grams of NaCl in 500 cm³ of water. (Molar mass of NaCl = 58.44 g/mol)

Answer: M = 0.171 mol/dm³

Question 2: A student needs 0.25 mol of sulphuric acid (H₂SO₄) to prepare 1 dm³ of solution. What mass of H₂SO₄ should they dissolve? (Molar mass of H₂SO₄ = 98.08 g/mol)

Answer: Mass = 24.52 grams

Question 1: Describe the steps involved in preparing a 0.1 mol/dm³ sodium hydroxide (NaOH) solution from solid NaOH.

Answer: Weigh a specific amount of NaOH (e.g., 4 g), dissolve it in less than 1 dm³ of water, then transfer to a volumetric flask and make up to the 1 dm³ mark, ensuring thorough mixing.

Question 2: Identify two safety precautions necessary when handling concentrated acids during solution preparation.

Answer: Wear eye protection and gloves; perform the procedure in a well-ventilated area and add acid slowly to water to prevent splashing.

Question 1: A 250 cm³ sample of a copper(II) sulphate solution contains 0.15 mol of CuSO₄. Calculate the concentration of the solution in mol/dm³ and explain what this value indicates about the solution.

Answer: Concentration = 0.6 mol/dm³; this indicates a relatively concentrated solution of copper sulphate.

Question 1: Explain how concentration measurements are crucial in the pharmaceutical industry when preparing medicines and solutions for injections.

Answer: Accurate concentration measurements ensure correct dosages, safety for patients, consistency in medicine efficacy, and compliance with regulations.

Question 1: Describe how you would prepare a 0.2 mol/dm³ solution of potassium permanganate (KMnO₄) starting from solid crystals. Include safety precautions, measurements, and calculations involved. Discuss the importance of accuracy in this process.

Answer: Begin by calculating the mass of KMnO₄ needed using its molar mass (158.04 g/mol): for 1 dm³ at 0.2 mol/dm³, mass = 31.6 grams. Weigh this accurately using a balance, dissolve it in less than 1 dm³ of distilled water in a beaker, then transfer to a volumetric flask and make up to the 1 dm³ mark. Wear safety goggles and gloves, handle the solid carefully to avoid spills, and add acid or base as required for specific reactions. Precise measurements are vital to ensure the solution's concentration is correct for subsequent reactions or experiments, avoiding errors that could compromise safety and results.