A gas mixture consists of N2, SO2, and Ar, where the mole fraction of N2 is 0.55 and the mole fraction of Ar is 0.25. If the mixture is at STP in a 5.0 L container, how many molecules of SO2 are present

2.7E22 molecules  of SO2

Explanation:

Mole Fraction of N2 = 0.55

Mole Fraction of Ar = 0.25

Mole Fraction of SO2 = ?

The mole fraction of a molecule/compound = 1

But Mole fraction of compound = Mole fraction of SO2 + Mole fraction of Ar + Mole fraction of N2

Mole Fraction of SO2 = 1 - (0.55 + 0.25)

Mole Fraction of SO2  = 0.20

Total Number of moles of gas at STP in 5.0L

1 mol = 22.4L

x mol = 5L

X = 5 / 22 = 0.2232 mol

Number of moles of SO2 = Mole Fraction * Number of moles of gas

Number of moles of SO2 = 0.2232 * 0.20 = 0.0446 moles

Upon conversion to molecules;

1 mole = 6.022E23 molecules

0.0446 mole = x

x = 0.0446 mol * 6.022E23 molecule/mol = 2.7E22 molecules  of SO2

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