To determine the weight of organic matter in the soil sample, we need to analyze the data provided and perform a simple calculation. Let's break down the steps clearly.
Step-by-Step Explanation
- Understanding the Data:
- The weight of the over-dried soil before burning is given as 50g.
-
The weight of the over-dried soil after burning is given as 28g.
-
Calculating the Weight of Organic Matter:
- The organic matter in the soil is what gets burned off when the soil is subjected to high temperatures. Therefore, the difference in weight before and after burning represents the weight of the organic matter.
- We can calculate the weight of organic matter using the formula:
[
\text{Weight of Organic Matter} = \text{Weight before burning} - \text{Weight after burning}
]
-
Plugging in the values:
[
\text{Weight of Organic Matter} = 50g - 28g = 22g
]
-
Final Answer:
- The weight of organic matter in the soil sample is 22g.
Explanation of Options
Now, let's evaluate the options provided:
-
A. 11g: This option is incorrect because it does not reflect the difference in weight calculated. It is half of the correct answer and suggests a misunderstanding of the burning process.
-
B. 22g: This is the correct answer. It accurately represents the weight of organic matter calculated from the difference in weight before and after burning.
-
C. 44g: This option is incorrect. It is double the correct answer and indicates a possible miscalculation or misunderstanding of the process of determining organic matter.
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D. 78g: This option is also incorrect. It exceeds the initial weight of the soil sample, which is not possible since burning cannot add weight. This suggests a fundamental misunderstanding of the concept.
Common Pitfalls
- Misunderstanding the Process: Some students may confuse the burning process with other soil tests and might not realize that organic matter is lost during burning.
- Calculation Errors: Simple arithmetic mistakes can lead to incorrect answers. Always double-check your calculations.
- Ignoring Units: Ensure that you are consistent with units (grams in this case) throughout your calculations.
Revision Summary
- The weight of organic matter is calculated by subtracting the weight of the soil after burning from the weight before burning.
- In this case, the calculation is: 50g (before) - 28g (after) = 22g (organic matter).
- The correct answer is B. 22g.
- Always verify your calculations and understand the process to avoid common mistakes.
By following these steps and understanding the reasoning behind the calculations, you can confidently determine the weight of organic matter in soil samples in future experiments.