2.1. A sample of dust from the air in a factory is collected on a glass slide. If dust on the slide was deposited from one cubic centimetre of air, estimate the mass of dust in g/m3 of air in the factory, given the number of particles in the various size ranges to be as follows: Size range (μm) 0-1 1-2 2-4 4-6 6-10 10-14 Number of particles (-) 2000 1000 500 200 100 40 It may be assumed that the density of the dust is 2600 kg/m3, and an appropriate allowance should be made for particle shape. (15) 2.2. Calcium carbonate (CaCO₃) is commonly used as a water treatment agent to neutralize acidity and reduce the solubility of heavy metals. In a pilot experiment, 2000 g of calcium carbonate is added to 2 m³ of pure water. Determine the following: 2.2.1. Calculate the concentration of bicarbonate ions (HCO₃⁻) in mg/L that results from the dissolution of calcium carbonate in the water. Assume complete dissociation of CaCO₃. (3) 2.2.2. Determine the concentration of calcium ions (Ca²⁺) in mg/L in the water after the addition of calcium carbonate. (3) 4 2.2.3. Given that the solubility product constant (Ksp) for CaCO₃ in water at 25 °C is K = 4.8 × 10⁻⁹, calculate the amount of undissolved calcium carbonate precipitate remaining in mg/L. (4) Note: Use appropriate equations for solubility and dissociation. Show all calculations and units in your final answers.