In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g of sample neutralised 10 mL of 1 M H2SO4. The percentage of nitrogen in the soil is

Options

A. `37.33`
B. `45.33`
C. `35.33`
D. `43.33`

Explanation

To find the percentage of nitrogen in the soil sample using Kjeldahl's method, we can follow these steps:

### Step 1: Identify the given data
- Mass of the soil sample = 0.75 g
- Volume of H2SO4 used = 10 mL
- Molarity of H2SO4 = 1 M

### Step 2: Calculate the normality of H2SO4
Normality (N) is calculated using the formula:
\[ \text{Normality} = \text{Molarity} \times n \text{ factor} \]

For sulfuric acid (H2SO4), the n factor is 2 because it can donate two protons (H+ ions) in reactions. Therefore:
\[ \text{Normality of H2SO4} = 1 \, \text{M} \times 2 = 2 \, \text{N} \]

### Step 3: Use the formula to calculate the percentage of nitrogen
The formula for calculating the percentage of nitrogen (N) in the sample is:
\[ \text{Percentage of Nitrogen} = \frac{1.4 \times \text{Normality of H2SO4} \times \text{Volume of H2SO4 (in L)}}{\text{Mass of the sample (in g)}} \]

First, convert the volume of H2SO4 from mL to L:
\[ 10 \, \text{mL} = 0.01 \, \text{L} \]

Now substitute the values into the formula:
\[ \text{Percentage of Nitrogen} = \frac{1.4 \times 2 \, \text{N} \times 0.01 \, \text{L}}{0.75 \, \text{g}} \]

### Step 4: Perform the calculation
Calculating the numerator:
\[ 1.4 \times 2 \times 0.01 = 0.028 \]

Now, divide by the mass of the sample:
\[ \text{Percentage of Nitrogen} = \frac{0.028}{0.75} \]

Calculating this gives:
\[ \text{Percentage of Nitrogen} = 0.03733 \text{ or } 3.733\% \]

To express this as a percentage:
\[ \text{Percentage of Nitrogen} = 3.733 \times 100 = 37.33\% \]

### Final Answer
The percentage of nitrogen in the soil sample is **37.33%**.

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