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Since air is a mixture, it does not have a "molar mass." However, for calculation purposes, it is possible to speak of its "effective molar mass." (An effective molar mass is a weighted average of the molar masses of a mixture's components.) If air at STP has a density of 1.285 g/L, its effective molar mass is ________ g/mol.

Respuesta :

Answer:

The effective molar mass of air at STP is 28.82 g/mol.

Explanation:

At STP, the value of pressure is 1 atm.

At STP, the temperature is equal to 273.15 K

P = 1atm, T = 273.15 K

Density of the gas at STP ,d= 1.285 g/L

[tex]PV=nRT[/tex] (Ideal gas equation)

[tex]PV=\frac{\text{Mass of air}}{\text{Molar mass of air(M)}}RT[/tex]

[tex]Density=\frac{Mass}{Volume}[/tex]

[tex]P\times M=d\times RT[/tex]

[tex]M=\frac{1.285 g/L}{1 atm}\times 0.0821 atm L/mol K\times 273.15 K[/tex]

M = 28.81 g/mol

The effective molar mass of air at STP is 28.82 g/mol.