Question 1: Define a salt in scientific terms.

Answer: A salt is an ionic compound formed from the reaction of an acid with a base, consisting of a metal or ammonium cation and a non-metal or polyatomic anion.

Question 2: Explain the general method used to prepare a salt via a neutralisation reaction.

Answer: A salt is prepared by reacting an acid with an alkali (base), producing a salt and water. The acid and alkali are mixed until neutralisation occurs, often followed by filtration and evaporation to obtain the salt.

Question 3: What are the key safety precautions to consider when preparing salts in the laboratory?

Answer: Wear safety goggles and gloves, handle acids and alkalis with care, work in a well-ventilated area, and dispose of chemicals according to safety guidelines.

Question 1: Calculate the mass of sodium chloride (NaCl) produced when 0.5 mol of hydrochloric acid (HCl) reacts completely with excess sodium hydroxide (NaOH). (Atomic masses: Na = 23, Cl = 35.5, H = 1, O = 16)

Answer: NaCl molar mass = 58.5 g/mol; mass = moles × molar mass = 0.5 × 58.5 = 29.25 grams.

Question 2: A student needs to prepare 100 g of potassium sulphate (K₂SO₄). How many moles of potassium sulphate is this? (Atomic masses: K=39, S=32, O=16)

Answer: Molar mass of K₂SO₄ = (2×39) + 32 + (4×16) = 174 g/mol; moles = mass / molar mass = 100 / 174 ≈ 0.575 mol.

Question 1: Outline a basic procedure for preparing copper sulphate (CuSO₄) salt from copper oxide and sulphuric acid, including safety considerations.

Answer: Mix excess copper oxide with dilute sulphuric acid in a beaker, heat gently to dissolve the oxide, then filter the solution to remove unreacted solids. Evaporate the filtrate to obtain crystals of copper sulphate. Use safety goggles and gloves when handling acids and heating, work in a well-ventilated area, and dispose of waste safely.

Question 1: A factory produces 500 kg of sodium carbonate (Na₂CO₃) annually. If the process involves reacting sodium hydroxide with carbon dioxide, estimate the amount of sodium hydroxide (NaOH) used, assuming 100% efficiency. (Atomic masses: Na=23, C=12, O=16, H=1)

Answer: Molar mass of Na₂CO₃ = (2×23)+12+(3×16)=106 g/mol. Moles of Na₂CO₃ = 500,000 g / 106 ≈ 4717 mol. Since 2 mol NaOH reacts per mol Na₂CO₃, moles of NaOH = 2 × 4717 ≈ 9434 mol. Mass of NaOH = 9434 mol × 40 g/mol = 377,360 grams or 377.36 kg.

Question 1: Describe the process and chemical reactions involved in producing an insoluble salt, such as barium sulphate, from soluble barium chloride and sodium sulphate solutions.

Answer: Mix aqueous solutions of barium chloride and sodium sulphate. Barium sulphate precipitates out as an insoluble solid: BaCl₂ + Na₂SO₄ → BaSO₄ (s) + 2 NaCl. Filter the mixture to collect the precipitate, wash it with water, and dry to obtain pure barium sulphate salt.

Question 2: Explain why some salts, such as potassium sulphate, are more suitable for agricultural use than others.

Answer: Potassium sulphate is soluble and provides essential nutrients without adding chloride ions, which can be harmful to plants. It is also less corrosive and has a neutral pH, making it suitable for crops.

Question 1: Describe how the production of sodium chloride (table salt) has evolved from traditional evaporation methods to modern industrial processes.

Answer: Traditional methods involved evaporating seawater in salt pans, while modern industry uses solution mining and vacuum evaporation from brine sources, allowing large-scale, efficient salt production.

Question 2: Identify two industries that rely on salt production, and explain its importance in each.

Answer: The food industry uses salt for preservation and flavouring; the chemical industry uses salt as a raw material for producing chemicals like sodium hydroxide, chlorine, and caustic soda.