Which of the following best explains what occurs when pure sulfuric acid is added to water?
The molecules of sulfuric acid and water mix without reacting. The sulfuric acid causes the water to ionise but it remains as H2SO4 molecules in the solution. The sulfuric acid molecules react with water molecules to form ions. The ions present in the sulfuric acid lattice dissociate into the water. Correct. Incorrect • A precipitation reaction can be used to remove the hardness from water. Ca2+(aq) + CO3 2–(aq) → CaCO3(s) Which of the following is the best description for why this process works? The carbonate ions are neutralised. The amount of solid in the water is reduced. The calcium ions are taken out of solution. The calcium carbonate improves the cleaning action of soap. Correct, once in the solid they no longer affect the properties of the solution. Incorrect • Four solutions of sodium chloride were labelled with concentrations measured with different units. Which of the following would have the highest concentration? (Assume density of the solution is 1.00 g mL–1) 2.0% by mass
