Which gas has the largest density

density = molar mass in grams/22.4 L = ?g/L

Would it be Cl2 since it’s density is 3.214 g/l?

I don't know how you obtained 3.214 although that is close. Did you calculate the density of the others and compare? Actually you don't need to do that. Since density = molar mass/22.4 then

Cl2 = 71/22.4 = ?
Ar = 40/22.4 = ?
O2 = 32/22.4 = ?
He = 4/22.4 = ?
and since the denominator is the same then the one with the highest density must be the one with the largest numerator and that is Cl2.

To determine which gas has the largest density among Cl2, Ar, O2, and He, we need to know the molar mass of each gas.

The molar mass is the mass of one mole of a substance and is expressed in grams per mole (g/mol).

Let's find the molar mass of each gas:

1. Cl2 (Chlorine gas):
The molar mass of Cl2 can be calculated by adding the atomic masses of two chlorine atoms. The atomic mass of chlorine is 35.45 g/mol. Therefore, the molar mass of Cl2 is 35.45 + 35.45 = 70.90 g/mol.

2. Ar (Argon gas):
Argon is a noble gas with the atomic number 18. Therefore, the atomic mass of argon is 39.95 g/mol.

3. O2 (Oxygen gas):
The molar mass of O2 can be determined by adding the atomic masses of two oxygen atoms. The atomic mass of oxygen is approximately 16.00 g/mol. Thus, the molar mass of O2 is 16.00 + 16.00 = 32.00 g/mol.

4. He (Helium gas):
Helium is the lightest noble gas and has an atomic mass of 4.00 g/mol.

Now that we know the molar masses of each gas, we can compare their densities. Density is defined as mass per unit volume.

To compare the densities, we need to divide the molar mass by the molar volume, which is the volume occupied by one mole of a substance. At standard temperature and pressure (STP), the molar volume of any ideal gas is approximately 22.4 liters.

To calculate the density, divide the molar mass by the molar volume:

Density = Molar Mass / Molar Volume

Let's calculate the densities:

1. Cl2:
Density of Cl2 = 70.90 g/mol / 22.4 L/mol = 3.17 g/L

2. Ar:
Density of Ar = 39.95 g/mol / 22.4 L/mol = 1.78 g/L

3. O2:
Density of O2 = 32.00 g/mol / 22.4 L/mol = 1.43 g/L

4. He:
Density of He = 4.00 g/mol / 22.4 L/mol = 0.18 g/L

Therefore, among the given options, Cl2 has the largest density with a value of 3.17 g/L.