Given that a sample of air is made up of nitrogen, oxygen, and argon in the mole fraction 0.78 n2, 0.21 o2, and 0.010 ar, what is the density of air at standard temperature and pressure?

The density is 1.29g/L

Explanation:

Step 1: Data given

Mol fraction of N2 = 0.78

Mol fraction of O2 = 0.21

Mol fraction of Ar = 0.010

Molar mass N2 = 28 g/mol

Molar mass O2 = 32 g/mol

Molar mass of Ar = 39.95 g/mol

Volume = 22.4 Lat STP

Molar volume = 22.4mol/L at STP

Step 2: Calculate moles

Total moles of sample = 1.00 moles

N2 = 0.78 mol

O2 = 0.21 mol

Ar = 0.01 mol

Step 3: Calculate mass

Mass = moles * molar mass

Mass N2 = 0.78 mol * 28 g/mol = 21.84 grams

Mass O2 = 0.21 mol * 32 g/mol = 6.72 grams

Mass Ar = 0.01 mol * 39.95 g/mol = 0.3995 grams

Total mass in 1 mol of gas = 28.9595 grams

Step 4: Calculate density

Density = mass / volume

Density 28.9595 grams / 22.4 L

Density = 1.29 g/L

The density is 1.29g/L

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