Question

A Vi = 10-3 m3 chamber of a gas bottle contains some argon gas (atomic weight = 0.040 kg/mole) at a pressure of 104 Pa and a temperature of 34� C. 1)What is the number density of atoms in this chamber? N/V =

Answer 1

Volume = 10^-3 m^3 = 1 L

1 m^3 = 1000L

molar mass of Ar = 0.040 kg /mol = 40 g /mol

T = 34 + 273 = 307 K

P = 104 Pa

1 atm = 1.01325 x 10^5 Pa

pressre P = 1 .03 x 10^-3 atm

P V = n RT

P V = W R T / M

1.03 x 10^-3 x 1 = W x 0.0821 x 307 / 40

W = 0.0016 g

moles = mass / molar mass

           = 0.0016 / 40

            = 4 x 10^-5

1 mol contain ------------------------> 6.023 x 10^23 atoms

4 x 10^5 mol contain = 4 x 10^5 x 6.023 x 10^23 = 2.41 x 10^19 atom

number density = N/V

                        = 2.41 x 10^19 atom / 10^-3

                        = 2.41 x 10^22 atom /m^3

number density = 2.41 x 10^22 atom /m^3