In Victor Meyer's experiment, 0.6 g of a volatile substance displaced 112 mL of air at S.T.P. Find the molecular mass of the substance.

Answer

To find the molecular mass of the volatile substance in Victor Meyer's experiment, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Given Data:**
- Mass of the volatile substance (m) = 0.6 g
- Volume of air displaced (V) = 112 mL = 0.112 L (since 1 L = 1000 mL)
- Standard Temperature and Pressure (STP):
- Temperature (T) = 273 K
- Pressure (P) = 1 atm
- Ideal Gas Constant (R) = 0.0821 L·atm/(K·mol)

2. **Use the Ideal Gas Equation:**
The ideal gas equation is given by:
\[ PV = nRT \]
where:
- P = pressure
- V = volume
- n = number of moles
- R = gas constant
- T = temperature

3. **Rearranging the Ideal Gas Equation:**
We can express the number of moles (n) as:
\[ n = \frac{PV}{RT} \]

4. **Substituting the Values:**
Substitute the known values into the equation:
\[ n = \frac{(1 \text{ atm})(0.112 \text{ L})}{(0.0821 \text{ L·atm/(K·mol)})(273 \text{ K})} \]

5. **Calculating n:**
First, calculate the denominator:
\[ 0.0821 \times 273 = 22.4143 \text{ L·atm/(mol)} \]
Now, calculate n:
\[ n = \frac{0.112}{22.4143} \approx 0.00499 \text{ mol} \]

6. **Relate Moles to Mass and Molecular Mass:**
The number of moles (n) is also related to mass (m) and molecular mass (M) by the formula:
\[ n = \frac{m}{M} \]
Rearranging gives:
\[ M = \frac{m}{n} \]

7. **Substituting the Values for M:**
Substitute the values of mass and moles:
\[ M = \frac{0.6 \text{ g}}{0.00499 \text{ mol}} \approx 120.24 \text{ g/mol} \]

8. **Final Answer:**
The molecular mass of the volatile substance is approximately **120 g/mol**.