# What is the molar mass of the unknown gas in a flask?

What is the molar mass (g mol^-1) of the gas?

Final answer: Using the Ideal Gas Law, and converting the pressure and temperature to appropriate units, we can calculate the number of moles of the gas present. We then calculate molar mass by dividing the mass by the number of moles, resulting in a molar mass of 47.51 g/mol for the unknown gas.

## Calculating the Molar Mass of the Unknown Gas

**To calculate the molar mass of the unknown gas, we can use the Ideal Gas Law formula:**

PV = nRT

Where:

P is pressure,

V is volume,

n is the number of moles of gas,

R is the ideal gas constant,

T is the temperature.

First, we convert the pressure of 626 mmHg to atmospheres: 626 mmHg / 760 = 0.8237 atm.

Next, we convert the temperature of 21.8 °C to Kelvin: 21.8 °C + 273.15 = 294.95 K.

The molar volume of any ideal gas at STP is 22.4 L/mol.

Therefore, we calculate the number of moles (n) using the formula:

n = (0.8237 atm * 3.15 L) / (0.0821 L·atm/K·mol * 294.95 K) = 0.10651 mol

Finally, we calculate the molar mass of the unknown gas:

Molar Mass = mass / moles = 5.06 g / 0.10651 mol = 47.51 g/mol

So, the molar mass of the unknown gas in the flask is 47.51 g/mol.