Waec Model Questions Vol1 2022 Agricultural Science Question 2
Practice practical question 2 from the 2022 Waec Model Questions Vol1 Agricultural Science examination. This question covers Soil chemical analysis, Organic carbon determination, Laboratory error identification .
A soil sample is analysed for organic carbon using the Walkley‑Black dichromate oxidation method. The procedure is as follows: 1. 5.0 g of air‑dry soil is digested with excess 0.5 N potassium dichromate in the presence of sulphuric acid. 2. After digestion, the excess dichromate is titrated with 0.5 N ferrous sulphate solution. 3. A blank titration (no soil) is also performed. The titration readings obtained are: - Blank titration (B): 10.0 mL of 0.5 N FeSO₄. - Sample titration (S): 6.2 mL of 0.5 N FeSO₄. Using the Walkley‑Black formula, determine: (a) % organic carbon in the soil sample. (b) % organic matter (assume %OM = %C × 1.724). (c) Identify one probable source of error in the procedure and suggest a precaution to minimise it.
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This is Waec Model Questions Vol1 2022 Agricultural Science Question 2. It is one of the practical questions from the 2022 Waec Model Questions Vol1 Agricultural Science examination.
The question covers Soil chemical analysis, Organic carbon determination, Laboratory error identification .
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