At this pressure, how many molecules of air would there be in a 20 ∘C experimental chamber with a volume of 0.020 m3?

Explanation: The lowest pressure in a laboratory is 4.0*10^-11Pa

Using Ideal gas equation

PV = nRT

P = 4.0*10^-11Pa

V = 0.020m^3

T = 20+273 = 293k

n=number of moles = m/A

Where m is the number of molecules and A is the Avogradro's number=6.02*10²³/mol

R=8.314J / (mol * K)

PV = m/A (RT)

4.0*10^-11 * 0.020 = m/6.02*10²³ (8.314*293)

m = 4.0*10^-11*0.020*6.02*10^23 / (8.314*293)

m = 1.98*10^8 molecules

Therefore, the number of molecules is 1.98*10^8