Question

Calculate the critical temperature critical pressure and critical volume of a real gas

Answer 1

The real gas equation is given as( P+n^2a/V^2)(V-nb)=nRTwhere n= no. of molesa & b are Van-der Waal constant. “a” signifies the attraction between the molecules and “b” is volume of a single molecule of the gas.The critical point is the point on P-V plane isotherm where 1st and 2nd derivatives of P w.r.t V is zero(Critical point is a saddle point on P-V isotherm). After solving the got equations and given real gas equation we getV*=3nb, T*=(8a/27Rb) and P*=a/27b^2where P*, V*,T* are critical pressure, critical volume and critical temperature.we see that P*V*/RT* = 3n/8if we define Pr=P/P*, Vr=V/V*, and Tr= T/T* (These are reduced quantities ) then we get Reduced equation of state:(Pr+3/Vr^2)(Vr-1/3)=(8/3n)TrSo all the isotherms of P-V plane will lie on a single curve(reduced equation of state).The critical point is that point at which the properties of the two phases(here liquid and gas) become identical….

Answer 2

Answer:

By polishing the surface, as polishing makes the surface smooth and friction can be reduced. Using lubricants such as oil or grease can reduce the friction between the surfaces. When objects are rolled over the surface, the friction between the rolled object and surface can be reduced by using ball bearings.13-Dec-2020