Final answer:
The true concentration of benzene in the lab measured by this method is 1093.54 mg/L.
Step-by-step explanation:
To determine the true concentration of benzene in the laboratory, we can use the ideal gas law and the concept of partial pressure. First, we need to convert the temperature to Kelvin and the pressure to pascals.
The temperature in Kelvin is 35 + 273 = 308 K,
and the pressure in pascals is 740 mmHg * 133.322 = 98621.48 Pa.
Next, we can use the equation:
P1/T1 = P2/T2
Where P1 and T1 are the initial pressure and temperature, and P2 and T2 are the final pressure and temperature. We can rearrange this equation to solve for P2:
P2 = P1 * T2 / T1
Plugging in the values, we get:
P2 = 98621.48 * (295.15 / 308)
= 94289.19 Pa
This is the final pressure of the benzene in the Mylar bag. Now, we can use the ideal gas law to find the number of moles of benzene:
n = (P * V) / (R * T)
Where n is the number of moles, P is the pressure, V is the volume, R is the ideal gas constant (0.0821 L·atm/(mol·K)), and T is the temperature in Kelvin. Plugging in the values, we get:
n = (94289.19 * 0.005) / (0.0821 * 295.15)
= 0.07 mol
Finally, we can calculate the concentration of benzene in the lab:
concentration = mass / volume
Given that the concentration is 10,200 mg/m3 and we collected 5 liters of air, we can calculate the mass of benzene:
mass = concentration * volume
= 10200 * 5
= 51000 mg
Using the molar mass of benzene (78.11 g/mol):
mass = 0.07 mol * 78.11 g/mol
= 5.4677 g
Therefore, the true concentration of benzene in the laboratory measured by this method is:
concentration = mass / volume
= 5.4677 g / 5 L
= 1.09354 g/L
= 1093.54 mg/L