To determine the percentage of organic matter in the soil sample, we can follow a systematic approach using the data provided. Here’s how to do it step-by-step:
Step 1: Understand the Data
- Weight of over-dried soil before burning: 50g
- Weight of over-dried soil after burning: 28g
Step 2: Calculate the Weight of Organic Matter
The weight of organic matter in the soil can be calculated by finding the difference between the weight of the soil before burning and the weight after burning. This is because burning the soil will remove the organic matter, leaving behind only the inorganic components.
Formula:
[ \text{Weight of Organic Matter} = \text{Weight before burning} - \text{Weight after burning} ]
Calculation:
[ \text{Weight of Organic Matter} = 50g - 28g = 22g ]
Step 3: Calculate the Percentage of Organic Matter
To find the percentage of organic matter in the soil, we use the formula:
Formula:
[ \text{Percentage of Organic Matter} = \left( \frac{\text{Weight of Organic Matter}}{\text{Weight of Soil before burning}} \right) \times 100 ]
Calculation:
[ \text{Percentage of Organic Matter} = \left( \frac{22g}{50g} \right) \times 100 ]
[ \text{Percentage of Organic Matter} = 0.44 \times 100 = 44\% ]
Conclusion
The percentage of organic matter in the soil sample is
44%. Therefore, the correct option is
B.
Explanation of Other Options
-
Option A (22%): This option represents the weight of organic matter itself (22g) but does not reflect the percentage of organic matter in relation to the total weight of the soil sample. Thus, it is incorrect.
-
Option C (56%): This option could be mistakenly calculated by subtracting the percentage of organic matter from 100%. However, this is not a valid method for determining the percentage of organic matter. The correct calculation shows that the organic matter is 44%, not 56%.
-
Option D (60%): This option is also incorrect as it does not relate to any calculation derived from the data provided. It does not reflect the actual weight of organic matter or its percentage in the soil sample.
Common Pitfalls
- Confusing weight with percentage: It’s important to remember that the weight of organic matter (22g) is not the same as its percentage (44%).
- Incorrectly calculating the percentage: Always ensure to divide the weight of organic matter by the total weight of the soil before burning, not after.
Revision Summary
- The percentage of organic matter is calculated by comparing the weight of organic matter to the total weight of the soil sample.
- The correct formula for percentage is: (\left( \frac{\text{Weight of Organic Matter}}{\text{Total Weight}} \right) \times 100).
- The weight of organic matter is found by subtracting the weight after burning from the weight before burning.
- The correct answer for the percentage of organic matter in this case is 44% (Option B).