Which statement is invalid regarding a closed system Energy

Which statement is invalid regarding a closed system? Energy can transfer across the boundary of the closed system. The mass of the closed system remains constant The volume of the closed system always remains constant. The pressure of the closed system may change with time. Which statement is valid regarding a poly tropic process? The pressure of the closed system always remains constant during a polytropic process. The volume of the closed system always remains constant during a polytropic process. The temperature of the closed system always remains constant during a poly tropic process. Heat may transfer across the boundary\' of the closed system during a poly tropic process. Which statement is invalid regarding a specific heat: c_v and c_p are properties. They are intensive properties. c_v and c_p are applied to any substance undergoing any process. c_v is related to the changes in internal energy and c_p to the changes in enthalpy. c_v is always greater than

Solution

1.C:Cylinder piston system is considered as closed system.As the system advances volume changes hence volume is not fixed in closed system

2.D:Unlike adiabatic process,the heat exchange takes place in polytropic process.for polytropic process PVⁿ=Constant and TⁿP^(1-n) so none of pressure volume or temperature is constant

3.D:When gas is heated at Constant Pressure (Cp) it requires more heat energy as there is change is in internal energy as well as external work done .But in case of Constant Volume (Cv) there is no external work done,so that the given heat has to increase only external energy .Therefore Cp is always greater than Cv.

4:C:work is done to compress so workdone on system is negative

    Given: P1=300Kpa V1=8 litres=8*10^-3 m³    V2=2litres

      for isothermal process W=P1*V1*ln(V2/V1)

         W=300*10³ *8*10^-3 *ln(2/8) =3.327KJ