The pH scaleIB MYP Chemistry: Mind map

Exam questions on The pH scale

1. A swimming pool technician in Dubai measures the water with a digital pH probe and records a pH of 6.4. The recommended range for safe swimming is about 7.2 to 7.8.
   Explain why a pH probe is a better choice than universal indicator for the technician.2 marks
2. A student starts with hydrochloric acid of pH 1.0. She mixes 10 cm³ of this acid with 90 cm³ of distilled water and measures the pH of the new solution with a probe: it is 2.0. She then mixes 10 cm³ of this new solution with another 90 cm³ of distilled water, and the pH is 3.0.
   Describe the trend in pH as the acid is diluted and explain it in terms of hydrogen ions.2 marks
3. A student in Cape Town tests five solutions, P to T, with a pH probe. The readings are: P, pH 1.0; Q, pH 4.0; R, pH 7.0; S, pH 10.0; T, pH 13.0.
   State which solution is the most acidic, which is neutral and which is the most alkaline.3 marks