Question

An open flask sitting in a lab refrigerator looks empty, but it is actually filled with a mixture of gases called air. If the flask volume is 2.00 L, and the air is at standard temperature and pressure, how many gaseous molecules does the flask contain?

Answer 1

Answer: $67.4\times 10^{23}$ molecules are there in the flask

Explanation:

According to the ideal gas equation:

$PV=nRT$

P = Pressure of the gas = 1 atm    

V= Volume of the gas = 2.00 L

T= Temperature of the gas = 273 K    $0^00C=273K$

R= Gas constant = 0.0821 atmL/K mol

n= moles of gas

$n=\frac{RT}{PV}=\frac{0.0821\times 273}{1\times 2.00}=11.2$

According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number $6.023\times 10^{23}$ of particles.

1 mole of gaseous air contains =  $6.023\times 10^{23}$ molecules

11.2 moles of gaseous air contains =  $\frac{6.023\times 10^{23}}{1}\times 11.2=67.4\times 10^{23}$ molecules

$67.4\times 10^{23}$ gaseous molecules are contained in the flask.