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To determine the pH of garden soil, a sample was first saturated with distilled water in a petri dish - HSC - SSCE Chemistry - Question 32 - 2011 - Paper 1
Question 32
To determine the pH of garden soil, a sample was first saturated with distilled water in a petri dish. Barium sulfate powder was added to the surface of the sample, ... show full transcript
Worked Solution & Example Answer:To determine the pH of garden soil, a sample was first saturated with distilled water in a petri dish - HSC - SSCE Chemistry - Question 32 - 2011 - Paper 1
Step 1
Why is barium sulfate powder added when testing soil pH?
Answer
Barium sulfate powder is added to the soil sample to help suspend the soil particles in the solution and prevent them from settling. This ensures that the indicator reagents can interact more uniformly with the soil mixture, leading to more accurate pH measurement.
Step 2
Using the information given, select the plant that will grow well at the current soil pH, and justify your selection.
Answer
Based on the observed color changes of the indicators, the soil pH can be estimated around 6.6. The plant that can grow well in this range is the Carrot, which has an optimal pH range of 5.5 to 6.8. Thus, Carrot is the suitable plant for this soil pH.
Step 3
Outline the method you would use to test a natural indicator that has been prepared in the school laboratory.
Answer
To test a natural indicator, follow these steps:
- Prepare several test solutions of known pH (e.g., pH 4, 6, 7, 8).
- In separate test tubes, add a few drops of the natural indicator solution to each test solution.
- Observe and record the color changes occurring in the mixtures.
- Compare the observed colors against a pH scale to identify the pH range in which the indicator changes color.