Biology 2023 JAMB Past Questions - Question 6: 28 g soil sample was heated to a constant weight of 24g. When further heated to red hot and cooled, it weighed 18 g. What is the percentage of humus in the soil?

Correct Answer

B

Explanation

To find the percentage of humus in the soil, we need to understand the process described in the question. When the soil sample was initially heated to a constant weight of 24g, it likely lost moisture and other volatile components. Then, when it was further heated to red hot and cooled, it lost additional material, possibly organic matter like humus.Let's break down the steps:

1. Initial weight of the soil sample = 28g
2. After heating to a constant weight = 24g
3. After further heating to red hot and cooling = 18g

The weight loss from step 2 to step 3 represents the loss of additional material, likely organic matter such as humus.Weight loss = Initial weight - Final weight Weight loss = 24g - 18g Weight loss = 6gNow, to find the percentage of humus in the soil, we'll use the formula:Percentage of humus = (Weight loss / Initial weight) * 100%Substitute the values:Percentage of humus = (6g / 28g) * 100% Percentage of humus ≈ 21.43%So, the percentage of humus in the soil is approximately 21.43%.