What will be the standard molar volume of He, if its density is 0.1784 g/L at STP?

Options

A. 11.2 L
B. 22.4 L
C. 5.6 L
D. 2.8 L

Explanation

To find the standard molar volume of helium (He) given its density at STP (Standard Temperature and Pressure), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Density**:
Density (d) is defined as mass (m) per unit volume (V). The formula is:
\[ d = \frac{m}{V} \]

2. **Identify Given Values**:
We are given the density of helium:
\[ d = 0.1784 \, \text{g/L} \]

3. **Calculate the Mass of One Mole of Helium**:
The molar mass of helium (He) is approximately 4 g/mol. This means 1 mole of helium has a mass of 4 grams.

4. **Use the Density to Find the Volume of One Mole**:
Rearranging the density formula to find volume:
\[ V = \frac{m}{d} \]
Substituting the values for 1 mole of helium:
\[ V = \frac{4 \, \text{g}}{0.1784 \, \text{g/L}} \]

5. **Perform the Calculation**:
\[ V = \frac{4}{0.1784} \approx 22.4 \, \text{L} \]

6. **Conclusion**:
The standard molar volume of helium at STP is approximately 22.4 L.

### Final Answer:
The standard molar volume of He is approximately **22.4 L**.