Question 1: Define neutralisation in terms of acids and alkalis.

Answer: Neutralisation is a chemical reaction where an acid reacts with an alkali to produce a salt and water.

Question 2: Explain why the pH of a neutralisation mixture is close to 7.

Answer: Because the hydrogen ion concentration from the acid and the hydroxide ion concentration from the alkali cancel each other out, resulting in a neutral pH of around 7.

Question 1: Calculate the volume of 0.5 mol/dm³ hydrochloric acid (HCl) required to neutralise 25 cm³ of 0.2 mol/dm³ sodium hydroxide (NaOH).

Answer: Volume of HCl = (concentration of NaOH × volume of NaOH) / concentration of HCl = (0.2 mol/dm³ × 25 cm³) / 0.5 mol/dm³ = 10 cm³

Question 2: What mass of sodium chloride (NaCl) is formed when 50 cm³ of 0.1 mol/dm³ hydrochloric acid reacts completely with excess sodium hydroxide?

Answer: Moles of HCl = 0.1 mol/dm³ × 50 cm³ = 0.005 mol; NaCl formed = 0.005 mol; Molar mass of NaCl ≈ 58.5 g/mol; Mass = 0.005 mol × 58.5 g/mol = 0.2925 g

Question 1: Describe a simple procedure to determine the concentration of an unknown acid solution using neutralisation.

Answer: Titrate the unknown acid with a standard solution of a known alkali (e.g., sodium hydroxide). Add a few drops of a suitable indicator (e.g., phenolphthalein). Record the volume of alkali used to reach the endpoint (colour change). Use the titration data and the molarity of the alkali to calculate the molarity of the acid.

Question 2: List two safety precautions to observe when performing neutralisation titrations in the laboratory.

Answer: Wear safety goggles and gloves; handle acids and alkalis with care to avoid spills and skin contact.

Question 1: A student titrates 25 cm³ of an unknown acid with 0.1 mol/dm³ sodium hydroxide and requires 30 cm³ to reach the endpoint. Calculate the concentration of the acid.

Answer: Moles of NaOH = 0.1 mol/dm³ × 30 cm³ = 0.003 mol; Moles of acid = moles of NaOH = 0.003 mol; Concentration of acid = 0.003 mol / 0.025 dm³ = 0.12 mol/dm³

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

Answer: Antacids contain basic compounds that neutralise excess stomach acid (hydrochloric acid), relieving discomfort by restoring pH balance.

Question 2: Describe one industrial process that involves neutralisation reactions and its importance.

Answer: The production of salt via neutralisation, such as the manufacture of sodium chloride, is important for chemical manufacturing, food preservation, and water treatment. Neutralisation ensures the removal of excess acidity or alkalinity, stabilising the product.