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pH Scale and Indicators — Free MYP5 Chemistry Practice Questions
1QuestionMeasuring pH Using Electronic and Paper MetersConcept Practice
2 marks~3 minCriterion A
A water quality technician tests a river sample using two instruments:
Instrument A — an electronic pH meter with a probe and digital display
Instrument B — a strip of pH paper compared against a colour chart
Instrument A — an electronic pH meter with a probe and digital display
Instrument B — a strip of pH paper compared against a colour chart
a
State which instrument provides a numerical pH reading and which provides a colour-based reading. [1]
b
The technician records pH 4.2 using Instrument A and observes an orange colour using Instrument B. Explain one advantage of using Instrument A over Instrument B when precise pH data must be reported. [1]
Solutions
2QuestionStrong vs Weak Acids and Bases ConceptualAssessment Practice
2 marks~3 minCriterion C
Two beakers, A and B, each contain an aqueous solution of a different acid at equal concentration and volume. In Beaker A, the diagram shows a large number of ions separated from the acid molecules. In Beaker B, only a small number of ions are shown as separated, with most acid molecules remaining intact.
Deduce which beaker contains the strong acid, and justify your answer using evidence from the diagram. [2]
Deduce which beaker contains the strong acid, and justify your answer using evidence from the diagram. [2]
Solutions
3QuestionEveryday Substances and Their pH ValuesAssessment Practice
6 marks~9 minCriterion D
Farmers apply calcium hydroxide (lime) to acidic soils to raise pH and improve crop yields. Acidic soils (pH below 5.5) reduce nutrient availability and allow toxic metal ions to accumulate.
a
Explain how adding lime raises soil pH and identify two agricultural benefits this produces. [2]
b
Explain two environmental costs associated with the use of lime in agriculture. In your answer, refer to the calcination reaction and the effect of alkaline runoff on aquatic ecosystems. [2]
c
Evaluate the limitation of using pH as the sole indicator of soil quality, and justify whether liming alone is sufficient to ensure long-term soil health. [2]
Solutions
4QuestionEveryday Substances and Their pH ValuesAssessment Practice
3 marks~5 minCriterion B
The pH values of six household substances are listed below.
| Substance | pH value |
|---|---|
| Lemon juice | 2.5 |
| Vinegar | 3.0 |
| Milk | 6.5 |
| Pure water | 7.0 |
| Baking soda solution | 8.5 |
| Soap solution | 10.0 |
a
Identify the neutral substance from the list. [1]
b
Classify each remaining substance as acidic or basic, using its pH value as evidence. [1]
c
Analyse how the data shows a trend in acidity and alkalinity across the six substances, and explain what this trend reveals about the relationship between pH and the strength of acidity or alkalinity. [1]
Solutions
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