An open flask sitting in a lab fridge looks empty, but it is filled with a mixture of gases called air. Calculate the number of molecules of gas the flask contains if the flask volume is 2.50 L , and the air is at standard temperature and pressure (STP).

Respuesta :

Answer: The number of molecules of gas the flask contains is [tex]0.674\times 10^{23}[/tex]

Explanation:

According to ideal gas equation:

[tex]PV=nRT[/tex]

P = pressure of gas = 1 atm   (STP)

V = Volume of gas = 2.50 L

n = number of moles  = ?

R = gas constant =[tex]0.0821Latm/Kmol[/tex]

T =temperature = 273K (STP)

[tex]n=\frac{PV}{RT}[/tex]

[tex]n=\frac{1atm\times 2.50L}{0.0821 L atm/K mol\times 273K}=0.112moles[/tex]

According to Avogadro's law:

1 mole of gas at STP contains =[tex]6.023\times 10^{23}[/tex] molecules

Thus 0.112moles of gas at STP contains = [tex]\frac{6.023\times 10^{23}}{1}\times 0.112=0.674\times 10^{23}[/tex] molecules

The number of molecules of gas the flask contains is [tex]0.674\times 10^{23}[/tex]