Question

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).

Answer 1

Answer: The number of molecules of gas the flask contains is
`0.674* 10^(23)`

Step-by-step explanation:

According to ideal gas equation:

`PV=nRT`

P = pressure of gas = 1 atm (STP)

V = Volume of gas = 2.50 L

n = number of moles = ?

R = gas constant =
`0.0821Latm/Kmol`

T =temperature = 273K (STP)

`n=(PV)/(RT)`

`n=(1atm* 2.50L)/(0.0821 L atm/K mol* 273K)=0.112moles`

According to Avogadro's law:

1 mole of gas at STP contains =
`6.023* 10^(23)` molecules

Thus 0.112moles of gas at STP contains =
`(6.023* 10^(23))/(1)* 0.112=0.674* 10^(23)` molecules

The number of molecules of gas the flask contains is
`0.674* 10^(23)`