Photo AI
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 when testing soil pH to precipitate any sulfide ions that may interfere with the accuracy of the pH measurement. This ensures that the results obtained from the indicators reflect the actual pH of the soil solution.
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 indicator colors and the corresponding pH values, the soil appears to be slightly acidic (below 6.0). The only plant that can thrive in this pH range is 'Hydrangea Blue,' which prefers a pH of 4.0 to 5.0. Therefore, it is the most suitable plant for this soil.
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 prepared in the school laboratory, first, prepare several solutions with known pH values ranging from acidic to alkaline. Next, place small amounts of the natural indicator into each solution. Observe and record the color change of the indicator in each pH solution. Finally, compare these color results to determine the pH range at which the natural indicator changes color effectively.