Question 1: Define the pH scale and explain what pH values indicate about acidity or alkalinity.

Answer: The pH scale measures the concentration of hydrogen ions (H⁺) in a solution, ranging from 0 to 14. pH less than 7 indicates acidity, pH of 7 is neutral, and pH greater than 7 indicates alkalinity.

Question 2: Describe how the pH of a solution affects its properties and potential uses in industry.

Answer: The pH influences properties like corrosion, solubility, and reactivity. Acidic solutions are used in cleaning and food preservation, while alkaline solutions are used in manufacturing and water treatment.

Question 1: Calculate the hydrogen ion concentration (H⁺) in a solution with a pH of 3. Use the formula: [H⁺] = 10^(-pH).

Answer: 1 x 10^(-3) mol/dm³

Question 2: A solution has a hydrogen ion concentration of 1 x 10^(-5) mol/dm³. What is its pH?

Answer: pH = 5

Question 3: If a solution has a pH of 9, what is its hydroxide ion concentration (OH⁻)? Use the relation: pOH = 14 - pH, and [OH⁻] = 10^(-pOH).

Answer: 1 x 10^(-5) mol/dm³

Question 1: Outline the steps involved in measuring the pH of a solution using pH indicator paper. Include safety precautions and variables to control.

Answer: To measure pH with indicator paper, dip a strip into the solution, compare the colour change to a pH colour chart, and record the pH value. Safety precautions include wearing gloves and eye protection. Variables to control include consistent dipping time and avoiding contamination.

Question 2: A student tests three solutions with pH indicator paper and obtains colours corresponding to pH 4, 7, and 10. Describe the relative acidity or alkalinity of each solution.

Answer: The solution with pH 4 is acidic, pH 7 is neutral, and pH 10 is alkaline (alkaline/basic).

Question 1: A sample of rainwater has a pH of 5.6. Explain the possible causes and implications of this pH level.

Answer: The slightly acidic pH may be due to dissolved carbon dioxide forming carbonic acid. It can indicate pollution and may harm aquatic life if pH drops further.

Question 2: Explain how the pH of soil affects plant growth and how farmers might use this information in agriculture.

Answer: Soil pH influences nutrient availability; neutral pH is ideal for most plants. Farmers can adjust soil pH with lime or sulphur to optimise growth conditions.

Question 1: Describe how pH measurements are important in the manufacturing of pharmaceuticals.

Answer: pH must be carefully controlled to ensure drug stability, efficacy, and safety, as many medicines require specific pH conditions for optimal performance.

Question 2: How does understanding the pH of water help in environmental conservation efforts?

Answer: Knowing water pH helps detect pollution, prevent harmful conditions for aquatic life, and maintain ecological balance.