Question 1: Explain what the pH scale measures and its significance in chemistry.

Answer: The pH scale measures the acidity or alkalinity of a solution, indicating the concentration of hydrogen ions (H⁺). It ranges from 0 (most acidic) to 14 (most alkaline), with 7 being neutral.

Question 1: Describe how the concentration of hydrogen ions (H⁺) relates to pH value.

Answer: The pH is the negative logarithm of the hydrogen ion concentration: pH = -log[H⁺]. As [H⁺] increases, pH decreases, making the solution more acidic.

Question 2: What pH value would you expect from a strong acid compared to a weak acid?

Answer: A strong acid typically has a lower pH (closer to 0-3), indicating higher H⁺ concentration, while a weak acid has a higher pH (closer to 4-6).

Question 1: Calculate the hydrogen ion concentration [H⁺] in a solution with pH 3.

Answer: [H⁺] = 1.0 × 10⁻³ mol/dm³

Question 2: A solution has a hydrogen ion concentration of 2.5 × 10⁻⁵ mol/dm³. What is its pH?

Answer: pH = 4.60

Question 1: Describe the safety precautions you should take when handling acids in the laboratory.

Answer: Wear safety goggles, gloves, and a lab coat; handle acids with care to avoid spills and splashes; work in a well-ventilated area; and know the location of safety equipment.

Question 2: Identify the variables that need to be controlled when comparing the pH of different solutions in an experiment.

Answer: Variables include temperature, concentration of solutions, and the type of acid or alkali used.

Question 1: A student measures the pH of three solutions: Solution A (pH 2), Solution B (pH 7), Solution C (pH 12). Explain the relative acidity or alkalinity of each solution and their hydrogen ion concentrations.

Answer: Solution A is highly acidic with a high concentration of H⁺ ions; Solution B is neutral with a balanced H⁺ and OH⁻ concentration; Solution C is alkaline with a low H⁺ concentration and a high OH⁻ concentration.

Question 1: Explain how the pH scale is used in industry, providing at least two specific examples. Discuss the importance of maintaining correct pH levels in these contexts.

Answer: The pH scale is vital in industries such as agriculture, where soil pH affects crop growth, and in water treatment, to ensure safe drinking water. Maintaining correct pH levels prevents corrosion, optimises chemical reactions, and ensures safety and efficiency in processes.

Question 1: Describe how pH testing is used in the food industry to ensure product safety and quality.

Answer: pH testing ensures food products are within safe acidity or alkalinity ranges, affecting preservation, taste, and safety, such as in dairy, canned foods, and beverages.

Question 2: Discuss the role of pH sensors in environmental monitoring technologies.

Answer: pH sensors are used to monitor water quality in lakes, rivers, and oceans, helping detect pollution and ensure environmental health by providing real-time data on acidity levels.