Question 1: Concentration refers to the amount of solute present in a given quantity of solvent or solution. It is commonly expressed in units such as molarity (mol/dm^3), mass per volume (g/dm^3), or percentage. Understanding concentration helps in preparing solutions and predicting chemical reactions.

Answer: Concentration is the amount of solute in a given amount of solvent or solution, often expressed in molarity, g/dm^3, or percentage.

Question 1: Define molarity and explain how it is used to express concentration.

Answer: Molarity is the number of moles of solute per litre of solution, used to quantify concentration.

Question 2: Describe one safety precaution to consider when preparing concentrated hydrochloric acid solutions.

Answer: Always add acid to water slowly while stirring and wear appropriate protective equipment.

Question 1: Calculate the molarity of a solution prepared by dissolving 5 grams of sodium chloride (NaCl) in 250 cm^3 of solution. (Molar mass of NaCl = 58.44 g/mol)

Answer: M = 0.34 mol/dm^3

Question 2: A solution has a concentration of 2 mol/dm^3. How many grams of sulphuric acid (H2SO4, molar mass = 98.08 g/mol) are needed to prepare 500 cm^3 of this solution?

Answer: 9.80 grams

Question 1: Identify two variables that must be controlled when preparing a standard solution of potassium permanganate in the lab.

Answer: Volume of solution measured accurately and purity of the chemical.

Question 2: State one safety precaution to take when handling concentrated acids during solution preparation.

Answer: Use gloves and eye protection to prevent contact with skin and eyes.

Question 1: A student prepared a 0.5 mol/dm^3 solution of sodium hydroxide and used 25 cm^3 of it to neutralise 40 cm^3 of hydrochloric acid. What is the concentration of the hydrochloric acid?

Answer: 0.312 mol/dm^3

Question 1: A 10 g sample of sodium carbonate (Na2CO3, molar mass = 106 g/mol) is dissolved in water to make 2 dm^3 of solution. Calculate the molarity of the solution.

Answer: 0.047 mol/dm^3

Question 2: Explain why it is important to use a volumetric flask when preparing solutions of known concentration.

Answer: Using a volumetric flask ensures accurate and precise measurement of the solution volume, which is crucial for calculating and achieving the desired concentration.

Question 1: Explain how understanding solution concentration is important in the pharmaceutical industry.

Answer: It ensures correct dosages, effectiveness, and safety of medicines by accurately preparing solutions with precise concentrations.

Question 2: Describe a situation in daily life where concentration of a solution affects its use or effectiveness.

Answer: Diluting cleaning products to the correct concentration ensures they work effectively without causing damage or health risks.