Question 1: Define the term 'mole' in chemistry and explain its significance.

Answer: A mole is the amount of substance containing exactly 6.022 x 10^23 particles (atoms, molecules, or ions). It allows chemists to count particles by weight.

Question 1: Calculate the number of moles in 24 grams of water (H₂O). (Molar mass of H₂O = 18 g/mol)

Answer: Number of moles = mass / molar mass = 24 g / 18 g/mol = 1.33 mol

Question 2: How many particles are present in 2 moles of sodium chloride (NaCl)? (Use Avogadro's number: 6.022 x 10^23 particles/mol)

Answer: Particles = moles x Avogadro's number = 2 mol x 6.022 x 10^23 = 1.2044 x 10^24 particles

Question 1: Describe the key safety precautions to observe when preparing a molar solution of a chemical substance.

Answer: Wear protective gloves and goggles, work in a well-ventilated area, handle acids and other hazardous chemicals carefully, and label solutions clearly.

Question 2: Identify the independent variable, dependent variable, and control in an experiment where a student measures the effect of concentration on reaction rate using molar solutions.

Answer: Independent variable: concentration of the solution; Dependent variable: reaction rate; Control: volume of solution, temperature, and type of chemical used.

Question 1: A sample contains 3.01 x 10^24 particles of a substance. How many moles does this sample represent?

Answer: Moles = particles / Avogadro's number = 3.01 x 10^24 / 6.022 x 10^23 ≈ 5 mol

Question 2: If 0.5 mol of gas occupies a volume of 11.2 litres at room temperature and pressure (RTP), what volume does 1 mol occupy?

Answer: Volume per mol = 11.2 L / 0.5 mol = 22.4 L per mol

Question 1: Explain why the mole is a useful unit in chemistry, particularly when dealing with chemical reactions and quantities. (6 marks)

Answer: The mole provides a standard way to count particles by relating mass to the number of particles through molar mass. It simplifies calculations involving reactants and products, allowing chemists to predict yields, determine amounts needed for reactions, and compare substances accurately. Using the mole ensures consistency and precision across experiments and industries.

Question 1: Describe how the pharmaceutical industry uses the concept of moles when formulating medicines.

Answer: The industry uses moles to accurately measure active ingredients to ensure correct dosage, consistency, and safety in medicines by calculating the precise amount needed based on molar mass.

Question 2: Explain the importance of molar calculations in environmental science, such as analysing pollutants.

Answer: Molar calculations help quantify pollutant concentrations in air, water, or soil, enabling assessment of environmental impact, regulation compliance, and development of remediation strategies.