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

Answer: The pH scale measures the hydrogen ion concentration in a solution. pH values below 7 indicate acidity, pH of 7 is neutral, and above 7 indicate alkalinity or basicity.

Question 2: Describe how the concentration of hydrogen ions ([H+]) in a solution affects its pH value.

Answer: The higher the concentration of hydrogen ions, the lower the pH value, indicating a more acidic solution. Conversely, fewer hydrogen ions mean a higher pH, indicating a more alkaline solution.

Question 1: Calculate the hydrogen ion concentration [H+] in a solution with a pH of 3.0. Use the formula: [H+] = 10^(-pH).

Answer: 1.0 x 10^(-3) mol/dm^3

Question 2: A solution has a hydrogen ion concentration of 1 x 10^(-8) mol/dm^3. What is its pH value?

Answer: pH = 8

Question 1: Describe a safe method to test the pH of a household lemon juice sample. Include safety precautions.

Answer: Use pH test strips or a pH meter. Wear safety goggles and gloves to avoid contact with the acid. Place a small amount of lemon juice on the strip or immerse the pH meter’s probe into the sample, then compare the colour or reading to the pH scale. Wash hands afterwards.

Question 1: A scientist measures the pH of three different solutions: Solution A (pH 2), Solution B (pH 7), and Solution C (pH 12). Describe the relative acidity or alkalinity of each solution and explain how their hydrogen ion concentrations compare.

Answer: Solution A is strongly acidic with a high concentration of hydrogen ions. Solution B is neutral, with a hydrogen ion concentration of 1 x 10^(-7) mol/dm^3. Solution C is strongly alkaline with a low hydrogen ion concentration of 1 x 10^(-13) mol/dm^3. The concentration of H+ decreases as pH increases.

Question 1: Explain why pH measurements are important in environmental monitoring and provide an example of a real-world application.

Answer: pH measurements are vital for monitoring water quality, soil health, and pollution levels. For example, measuring the pH of river water helps assess pollution levels and the health of aquatic ecosystems, as extreme pH levels can harm organisms and disrupt ecological balance.

Question 1: Discuss how the pH scale is used in the food industry, giving a specific example of a product or process.

Answer: The pH scale is used to determine the acidity of foods, affecting flavour and preservation. For example, in cheese making, pH levels are monitored to ensure proper fermentation and texture.