Weight of a soil sample with can is 220 g and dry weight with can is 190 g. Weight of empty moisture can is 45 g. Calculate moisture content of soil sample.
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Always remember that gravimetric water content is calculated relative to the dry weight of the soil solids, not the wet weight.
Dry soil weight = (Dry weight with can) - (Empty can weight).
Water weight = (Wet weight with can) - (Dry weight with can).
Step 1: Understanding the Concept:
Soil moisture content on a dry weight basis (gravimetric water content, \(\theta_g\)) is defined as the ratio of the mass of water present in the soil to the mass of the dry soil solids, expressed as a percentage. Key Formula or Approach:
The gravimetric moisture content is calculated using the formula:
\[ \theta_g = \frac{W_w}{W_d} \times 100\% \]
where:
\(W_w\) is the weight of water removed from the soil,
\(W_d\) is the weight of the oven-dry soil solids. Step 2: Detailed Explanation:
Let us calculate each value from the given data:
Given:
1. Weight of wet soil + moisture can = \(220\text{ g}\)
2. Weight of oven-dry soil + moisture can = \(190\text{ g}\)
3. Weight of the empty moisture can = \(45\text{ g}\)
First, calculate the weight of water (\(W_w\)) removed from the soil sample during drying:
\[ W_w = (\text{Weight of wet soil} + \text{can}) - (\text{Weight of dry soil} + \text{can}) \]
\[ W_w = 220 - 190 = 30\text{ g} \]
Next, calculate the weight of the dry soil solids (\(W_d\)) by subtracting the empty can weight from the dry weight:
\[ W_d = (\text{Weight of dry soil} + \text{can}) - (\text{Weight of empty can}) \]
\[ W_d = 190 - 45 = 145\text{ g} \]
Now, substitute these values into the gravimetric water content formula:
\[ \theta_g = \frac{30\text{ g}}{145\text{ g}} \times 100\% \]
\[ \theta_g \approx 0.20689 \times 100\% \approx 20.69\% \]
Rounding this value to one decimal place gives \(20.7\%\).
Therefore, the gravimetric moisture content of the soil sample is \(20.7\%\). Step 2: Final Answer:
The moisture content of the soil sample is 20.7 %.
