(a) Using specimens A, C\(_{1}\), C\(_{2}\), D, E and F; carry out a test of a chemical property of the specimen labelled A and present your report under th...

Answer Details

Specimen A is a soil sample, and the chemical property tested is its reaction (pH), using distilled water (D), a beaker (E), a stirring rod (F) and red and blue litmus papers (C1 and C2).

(a) Report on the test of a chemical property of specimen A

• (i) Aim: To determine the reaction (pH) of the soil in specimen A, that is, whether it is acidic, neutral or alkaline.
• (ii) Procedure: Wash a beaker (E) and rinse it with distilled water. Put a small quantity of the soil (A) into the beaker and add distilled water (D). Stir the mixture thoroughly with the stirring rod (F) and allow it to stand for a few minutes to settle. Dip the red litmus paper (C1) and the blue litmus paper (C2), one at a time, into the soil solution and observe the change in colour.
• (iii) Observation: The red litmus paper (C1) turned blue, while the blue litmus paper (C2) remained unchanged.
• (iv) Conclusion: The soil in specimen A is alkaline (basic) in nature.

(b) Two probable causes of the observed soil condition (alkalinity)

• Continuous application of alkaline fertilisers such as potash, or over-liming of the soil.
• The chemical composition of the parent rock, and arid conditions in which basic salts accumulate rather than being leached away.

(c) Four reasons why the experiment is important in agriculture

• It enables the farmer to determine the pH of the soil.
• It guides the choice of crops to grow, since crops differ in the soil reaction they tolerate.
• It shows whether plant nutrients will be available to crops, since availability depends on soil pH.
• It helps in deciding the type of fertiliser or amendment (such as lime or sulphur) to apply.