Question 1: Define the term 'neutralisation' in the context of acids and alkalis.

Answer: Neutralisation is a chemical reaction in which an acid reacts with an alkali to produce a salt and water, resulting in a solution with a pH close to 7.

Question 2: Describe the mechanism by which acids react with alkalis during neutralisation.

Answer: Acids release hydrogen ions (H⁺) in solution, while alkalis release hydroxide ions (OH⁻). When these ions combine, they form water (H₂O), and the remaining ions form a salt.

Question 3: What is the typical pH range of a neutral solution?

Answer: Approximately 7.

Question 1: Calculate the volume of 0.1 mol/dm³ hydrochloric acid (HCl) required to neutralise 25 cm³ of 0.2 mol/dm³ sodium hydroxide (NaOH).

Answer: Using the formula: M₁V₁ = M₂V₂; M₁=0.1 mol/dm³, V₁=?, M₂=0.2 mol/dm³, V₂=25 cm³. Convert V₂ to dm³: 25 cm³ = 0.025 dm³. So, V₁ = (M₂ × V₂)/M₁ = (0.2 × 0.025)/0.1 = 0.05 dm³ or 50 cm³.

Question 2: If 30 cm³ of a 0.5 mol/dm³ hydrochloric acid is needed to neutralise a solution, what is the amount of salt (NaCl) produced? (Assuming complete neutralisation).

Answer: Number of moles of HCl = Molarity × Volume = 0.5 mol/dm³ × 0.03 dm³ = 0.015 mol. Since the reaction is 1:1, 0.015 mol of NaCl is produced.

Question 1: Outline the steps involved in titrating an acid with an alkali to find the neutralisation point.

Answer: First, fill a burette with the alkali solution. Add a few drops of a suitable indicator to the acid in a conical flask. Slowly add the alkali from the burette to the acid while swirling continuously. Watch for a colour change that signifies neutralisation. Continue until the indicator changes colour permanently, indicating the end point. Record the volume used.

Question 2: Identify two safety precautions that should be observed during neutralisation experiments.

Answer: Wear safety goggles to protect eyes from splashes, and handle acids and alkalis with care, using appropriate gloves and apparatus to prevent skin contact.

Question 1: A student measures 25 cm³ of hydrochloric acid (0.1 mol/dm³) and neutralises it with sodium hydroxide. The reaction produces 25 cm³ of salt solution. Explain what this data indicates about the molar ratio of acid to base.

Answer: The data suggests a 1:1 molar ratio between HCl and NaOH, as equal volumes of equal molarity are needed for neutralisation in this scenario.

Question 1: Explain how neutralisation reactions are used in treating indigestion with antacids.

Answer: Antacids contain bases that react with excess stomach acid (hydrochloric acid) to form salt and water, reducing acidity and relieving symptoms of indigestion.

Question 2: Describe a practical reason why industries must carefully control neutralisation processes when producing waste water.

Answer: Industries need to carefully control neutralisation to ensure that harmful acids or alkalis are completely neutralised before releasing waste water into the environment, preventing damage to aquatic life and ecosystems. Proper neutralisation also helps industries comply with environmental regulations and avoid penalties.