How to Calculate the Molar Mass of a Gas Using Density at STP

What is the molar mass of Freon-11 gas if its density is 6.13 g/L at STP?

Final answer: The molar mass of Freon-11 gas is 137.312 g/mol.

Answer:

To calculate the molar mass of a gas using its density at STP, you can follow these steps:

1. Identify the given information: In this case, we are given the density of Freon-11 gas as 6.13 g/L at STP.
2. Use the ideal gas law: The ideal gas law equation is PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature.
3. Determine the values at STP: At STP (Standard Temperature and Pressure), the pressure is 1 atm, the volume is 22.4 L/mol, and the temperature is 273 K.
4. Calculate the number of moles: Use the ideal gas law formula n = PV/RT to find the number of moles. Plugging in the values, n = (1 atm)(22.4 L/mol) / (0.0821 L·atm/mol·K)(273 K) = 1 mol.
5. Calculate the molar mass: The molar mass of a gas is equal to its density multiplied by the molar volume, which is 1 mol of gas occupying 22.4 L at STP. The density of Freon-11 gas is given as 6.13 g/L, so the molar mass is 6.13 g/L x 22.4 L/mol = 137.312 g/mol.

Explanation:

When calculating the molar mass of a gas using its density at STP, it is important to understand the relationship between density, volume, and molar mass. By utilizing the ideal gas law and the given density of the gas, you can determine the molar mass accurately.

In this specific case of Freon-11 gas, the density of 6.13 g/L indicates the mass of the gas per unit volume. At STP, the conditions are well-defined, making it easier to calculate the molar mass using the given density.

By following the steps outlined above, you can calculate the molar mass of any gas when its density at STP is known. Understanding these concepts can be beneficial in various chemistry-related calculations and applications.