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

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

Question 2: Explain the mechanism by which acids and alkalis neutralise each other.

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

Question 3: Calculate the volume of 0.1 mol/dm³ hydrochloric acid (HCl) required to neutralise 25 cm³ of 0.1 mol/dm³ sodium hydroxide (NaOH). (Use the reaction: HCl + NaOH → NaCl + H₂O)

Answer: Answer: 25 cm³ of HCl. Explanation: Moles of NaOH = concentration × volume = 0.1 mol/dm³ × 0.025 dm³ = 0.0025 mol. Since the reaction ratio is 1:1, volume of HCl needed = moles / concentration = 0.0025 mol / 0.1 mol/dm³ = 0.025 dm³ = 25 cm³.

Question 4: Identify the variables that need to be controlled during a neutralisation experiment to ensure accurate results.

Answer: Variables include the concentration and volume of acid and alkali, temperature, and purity of reactants.

Question 5: Which of the following is a typical indicator colour change during neutralisation? A) Red to blue B) Colourless to pink C) Orange to green D) Blue to yellow

Answer: B) Colourless to pink

Question 6: Complete the following sentence: When an acid reacts with an alkali, the products are a ______ and ______.

Answer: salt and water

Question 7: Describe a simple practical experiment to demonstrate neutralisation, including the safety precautions you would take.

Answer: A common experiment involves adding dilute hydrochloric acid to a small amount of sodium hydroxide solution until the indicator changes colour, indicating neutralisation. Safety precautions include wearing safety goggles, gloves, and working in a well-ventilated area. Handle acids and alkalis carefully to avoid spills and burns.

Question 8: A student adds 50 cm³ of hydrochloric acid (0.1 mol/dm³) to a beaker and then titrates with sodium hydroxide (0.1 mol/dm³). The titration requires 45 cm³ of alkali to reach neutralisation. Calculate the number of moles of NaOH used.

Answer: Answer: 0.0045 mol. Explanation: Moles of NaOH = concentration × volume = 0.1 mol/dm³ × 0.045 dm³ = 0.0045 mol.

Question 9: In industry, neutralisation reactions are used to treat wastewater. Explain how this process works and why it is important.

Answer: In wastewater treatment, acids or alkalis are added to neutralise harmful pH levels, ensuring the water is safe for the environment and human health. This process helps remove toxic substances and prevents damage to aquatic ecosystems and infrastructure.