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

Answer: Concentration is the amount of solute present in a given quantity of solvent or solution, typically measured in molarity (mol/dm³).

Question 2: Explain why it is important to know the concentration of a solution in a laboratory setting.

Answer: Knowing the concentration ensures accurate reactions, proper reagent use, and safety in experiments.

Question 3: What is the formula used to calculate concentration in molarity?

Answer: Concentration (mol/dm³) = moles of solute / volume of solution in dm³.

Question 4: Calculate the concentration of a solution prepared by dissolving 0.5 mol of sodium chloride in 2 dm³ of water.

Answer: Concentration = 0.5 mol / 2 dm³ = 0.25 mol/dm³

Question 5: If a 100 cm³ solution contains 0.02 mol of sulphuric acid, what is its concentration in mol/dm³?

Answer: Convert 100 cm³ to 0.1 dm³. Concentration = 0.02 mol / 0.1 dm³ = 0.2 mol/dm³

Question 6: Which of the following solutions has the highest concentration? A) 0.1 mol of solute in 1 dm³ B) 0.2 mol of solute in 2 dm³ C) 0.5 mol of solute in 5 dm³

Answer: All have the same concentration of 0.1 mol/dm³.

Question 7: Complete the sentence: A solution with a high concentration of solute has a ___________ colour compared to a dilute solution.

Answer: darker

Question 8: Describe a simple method to prepare a 0.5 mol/dm³ sodium hydroxide solution from solid NaOH.

Answer: Weigh out 20 g of solid NaOH (molar mass 40 g/mol), dissolve it in distilled water, and make up the volume to 1 dm³ in a volumetric flask.

Question 9: What safety precautions should be observed when preparing solutions of acids and alkalis in the laboratory?

Answer: Wear safety goggles and gloves, handle acids and alkalis carefully, and work in a well-ventilated area.

Question 10: In a factory, a chemical mixture contains 2 mol of solute dissolved in 10 dm³ of solution. How would you describe its concentration?

Answer: The concentration is 0.2 mol/dm³.

Question 11: Explain how concentration affects the rate of a chemical reaction in solution.

Answer: Higher concentration means more reactant particles are present in a given volume, increasing the likelihood of collisions and thus speeding up the reaction.