The mass of 0.4 mol Ar is 16 g. What is the molar mass of Ar atoms?

Options

A. `4 g mol^(-1)`
B. `6.4 g mol^(-1)`
C. `0.04g mol^(-1)`
D. `40 g mol^(-1)`

Answer

To find the molar mass of argon (Ar) given that 0.4 moles of argon has a mass of 16 grams, we can use the formula that relates moles, mass, and molar mass:

### Step-by-Step Solution:

1. **Identify the formula**: The relationship between moles, mass, and molar mass is given by the formula:
\[ \text{Number of moles} = \frac{\text{Mass (g)}}{\text{Molar mass (g/mol)}} \]

2. **Substitute the known values**: From the question, we know:
- Number of moles (n) = 0.4 mol
- Mass (m) = 16 g
- Molar mass (M) = ?

We can rearrange the formula to solve for molar mass:
\[ M = \frac{\text{Mass}}{\text{Number of moles}} \]

3. **Plug in the values**:
\[ M = \frac{16 \text{ g}}{0.4 \text{ mol}} \]

4. **Calculate the molar mass**:
\[ M = \frac{16}{0.4} = 40 \text{ g/mol} \]

5. **Conclusion**: The molar mass of argon (Ar) is 40 g/mol.

### Final Answer:
The molar mass of Ar atoms is **40 g/mol**.

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