Question 1: Define the Avogadro Constant and state its value in mol⁻¹.

Answer: The number of particles (atoms, molecules, or ions) in one mole of a substance; approximately 6.022 x 10²³ mol⁻¹.

Question 2: Explain why the Avogadro Constant is fundamental in converting between mass and number of particles.

Answer: Because it relates the number of particles to the amount of substance in moles, allowing calculation of particles from mass and vice versa.

Question 1: Calculate the number of molecules in 0.5 mol of water (H₂O).

Answer: Number of molecules = 0.5 mol x 6.022 x 10²³ mol⁻¹ = 3.011 x 10²³ molecules.

Question 2: What is the mass of 2.5 mol of aluminium (Al), given its molar mass is 26.98 g/mol? (Show your working.)

Answer: Mass = 2.5 mol x 26.98 g/mol = 67.45 g.

Question 1: Describe a simple experimental method to determine the molar mass of a gas using the ideal gas equation, assuming the gas is at a constant temperature and pressure.

Answer: Measure the mass of a known volume of the gas, record the temperature and pressure, then use PV=nRT to find moles (n). Divide mass by moles to find molar mass.

Question 2: Identify two safety precautions to consider when conducting experiments involving gases at high pressure.

Answer: Use appropriate pressure-rated equipment and conduct the experiment in a well-ventilated area or fume hood.

Question 1: A sample of sulphur dioxide (SO₂) has a mass of 64 g. Calculate the number of molecules present, given that the molar mass of SO₂ is 64.07 g/mol.

Answer: Number of moles = 64 g / 64.07 g/mol ≈ 1 mol; number of molecules = 1 mol x 6.022 x 10²³ mol⁻¹ ≈ 6.022 x 10²³ molecules.

Question 2: If a chemist increases the amount of substance from 1 mol to 2 mol, how does this affect the number of particles? Explain briefly.

Answer: The number of particles doubles, since particles are directly proportional to moles according to Avogadro's Constant.

Question 1: Explain how the Avogadro Constant is used in the pharmaceutical industry when producing medicines in precise doses.

Answer: It allows precise calculation of the number of molecules or particles in a given mass, ensuring accurate dosing and consistent drug formulation.

Question 2: Describe one technological application that relies on the understanding of the number of particles in a substance, and explain its relevance.

Answer: Nanotechnology relies on controlling individual molecules and atoms; understanding particle numbers enables precise manipulation at nanoscale for developing new materials and electronics.