A gas has a density of 1.25 g/L at STP. What is its molecular mass?

33.6

To find the molecular mass of a gas, we need to use the ideal gas law and the molar volume of ideal gases at standard temperature and pressure (STP).

First, let's write down the given information:
Density of the gas at STP = 1.25 g/L

At STP, the conditions are:
Temperature (T) = 273.15 K
Pressure (P) = 1 atm
Molar volume (V) = 22.4 L/mol

The ideal gas law equation is:
PV = nRT

Where:
P = Pressure (in atm)
V = Volume (in L)
n = Number of moles
R = Ideal gas constant (0.0821 L·atm/(mol·K))
T = Temperature (in K)

We can rearrange the equation to solve for the number of moles (n):

n = PV / RT

Now, let's plug in the values:

n = (1 atm)(22.4 L) / (0.0821 L·atm/(mol·K))(273.15 K)

n = 0.0272 mol

The molecular mass of a gas is the mass of one mole of that gas. Therefore, we can calculate the molecular mass by dividing the mass by the number of moles:

Molecular mass = Mass / Moles

Since the density is given in grams per liter (g/L), we can calculate the mass of one liter as follows:

Mass = Density × Volume

Mass = 1.25 g/L × 1 L

Mass = 1.25 g

Now, let's calculate the molecular mass:

Molecular mass = Mass / Moles

Molecular mass = 1.25 g / 0.0272 mol

Molecular mass ≈ 45.96 g/mol

Therefore, the molecular mass of the gas is approximately 45.96 g/mol.

To determine the molecular mass of a gas, we need to use the ideal gas law, which relates the pressure, volume, temperature, and number of moles of a gas.

At STP (Standard Temperature and Pressure), the conditions are defined as follows:
- Temperature = 0 degrees Celsius or 273.15 Kelvin
- Pressure = 1 atmosphere or 101.325 kilopascals
- Volume = 22.4 liters (the molar volume of a gas at STP)

The formula for the ideal gas law is:
PV = nRT

Where:
P = pressure
V = volume
n = number of moles
R = ideal gas constant
T = temperature

At STP, we can simplify the ideal gas law equation to:
PV = (1 mole)(0.0821 L·atm/mol·K)(273.15 K)

Now, let's calculate the number of moles of the gas.

n = PV / (RT)
= (1.25 g/L) / (0.0821 L·atm/mol·K)(273.15 K)
= 0.045 moles

The molar mass (Molecular mass) of a gas is given by its mass per mole. We can calculate it using the following equation:

Molar mass (Molecular mass) = mass / moles

Given that the density of the gas is 1.25 g/L:
Mass = Density x Volume

Mass = 1.25 g/L x 22.4 L

Mass = 28 g

Now we can calculate the molecular mass of the gas:

Molar mass (Molecular mass) = 28 g / 0.045 moles

Molar mass (Molecular mass) ≈ 622.22 g/mol

Therefore, the molecular mass of the gas is approximately 622.22 g/mol.

1 mole of the gas will occupy 22.4 L at STP. What is the mass of 22.4 L?