EMA_4314_HW2_solutions

EMA_4314_HW2_solutions - EMA 4314 HW 2 Solutions Discussion...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: EMA 4314 HW 2 Solutions Discussion Questions 2.2 Rewrite the two expressions as follows: (1) adiabatic p 1/V (2) isothermal p 1/V The physical reason for the difference is that, in the isothermal expansion, energy flows into the system as heat and maintains the temperature despite the fact that energy is lost as work, whereas in the adiabatic case, where no heat flows into the system, the temperature must fall as the system does work. Therefore, the pressure must fall faster in the adiabatic process than in the isothermal case. Mathematically, this corresponds to > 1. 2.4 The change in a state function is independent of the path taken between the initial and final states; hence for the calculation of the change in that function, any convenient path may be chosen. This may greatly simplify the computation involved and illustrates the power of thermodynamics. The following list includes only those state functions that we have encountered in the first two chapters. More will be encountered in later chapters. Temperature, pressure, volume, amount, energy, enthalpy, heat capacity, expansion coefficient, isothermal compressibility, Joule–Thomson coefficient. Exercises 2.1(a) The physical definition of work is dw = -F dz [2.5]. In a gravitational field the force is the weight of the object, which is F = mg. If g is constant over the distance the mass moves, dw may be integrated to give the total work: =   =   =  = ,  =  : =  (65 ) 9.81 (4.0 ) = 2.6 × 10  = 2.6 × 10    : =  (65 ) 1.60 (4.0 ) = 4.2 × 10  = 4.2 × 10   2.3(a) 2.4(a) For a perfect gas at constant volume = = , ,= = = × , = =   (1.00 ) = 1.33 (400 300 ) ) = (1.00 8.314 w = 0 (constant volume); q = (400 300 ) = 1.25 × 10  = +1.25 = 1.25 0 = +1.25 2.8(a) q = H, since pressure is constant 2.11(a) 2.12(a) 2.15(a) In an adiabatic process, the initial and final pressures are related by (eqn 2.29) = Where = = = .  ( .  )( . .   ) = 1.40 2.16(a) 2.23(a) 2.28(a) 2.31(a) 24.8 1.00  = 3.9 × 10 3.9 × 10 (298) × ln  = 8.314 + = 8.05 × 10  = +8.05 × 10  + 131 = 7.92 × 10   2.33(a) 2.34(a) =( = , =  (15 )  = , = ( ) +7.2  ( ,  )  [  ( 75 )=+ = +8.1  ,   ) = +8.1 Problems 2.4 The virial expression for pressure up to the second coefficient is 2.18 2.22 A function has an exact differential if its mixed partial derivatives are equal. That is, f (x,y) has an exact differential if 2.24 2.36 = 1 ( 1 )= ( = 1  [  ) 1 × ( ) +( 2  [ ) 2.35] ...
View Full Document

This note was uploaded on 11/16/2011 for the course EMA 4314 taught by Professor Phillpot during the Fall '10 term at University of Florida.

Ask a homework question - tutors are online