Question

vacuum line is lowered to a pressure of 1.3kpa and 77 k find the number of moles per mm3. Assume that R= 8.31 JK-1 mol-1

Answer 1

The number of moles per mm³=2.032 x 10⁻⁹

Further explanation

In general, the gas equation can be written

`\large {\boxed {\bold {PV = nRT}}}`

where

P = pressure, atm , N/m²

V = volume, liter

n = number of moles

R = gas constant = 0.082 l.atm / mol K (P= atm, v= liter),or 8.314 J/mol K (P=Pa or N/m2, v= m³)

T = temperature, Kelvin

P=1.3 kPa=1.3.10³ N/m²

T = 77 K

R = 8.31 J/mol.K

`\tt PV=nRT\\\\(n)/(V)=(P)/(RT)\\\\(mol)/(m^3)=(1.3* 10^3)/(8.31* 77)\\\\(mol)/(m^3)=2.032\\\\2.032(mol)/(m^3)* (m^3)/(10^9cm^3)=2.032* 10^(-9)(mol)/(cm^3)`