these questions deal with my class introduction to thermodynamics of materials s

Question

these questions deal with my class introduction to thermodynamics of materials science.

PROBLEM 2 A rigid-walled cylinder is fitted with a rigid, weightless, frictionless piston. The cylinder contains 4.000 moles of Hz0 at 100"C and 1.000 atm pressure. The pressure of the surroundings is 1.000 atm. The cylinder is heated to (reversibly) convert H Ou to H Ogl at 100 C and 1.000 atm pressure, Calculate the amount of work done on the system (the H20) in the process. Express the answer in units of joules. PROBLEM 3 Three (3.00) moles of an ideal gas expands reversibly and isothermally at 400.0° C as pressure is reduced from 3.20 atm to 1.25 atm. Calculate the work done on the system; express the answer in units of joules.

Explanation / Answer

Problem 2)

As heat is given to the system,it is converted into internal energy of the system and work (P-V or pressure- volume work done by the system.(first law of thermodynamics)

Mathematically,

Q=U+W ,Where Q=heat added to the system

W=PV= work done by the system

U=change in internal energy

For reversible process,slow heating

Q=0,heat is exchanged between system and surrounding at equal rate(thermodynamic equilibrium of system and surrounding.

No change in temperature so no change in internal energy or internal energy is constant

Also, no PV work done.

Q=W=0

Problem 3

Isothermal reversible expansion process

P1=3.20 atm

P2=1.25 atm

T=400C=273+400=673K

n =3.00 moles

R=universal gas constant=8.314j/K mol

w=nRT ln p1/p2=3.00 moles*8.314 J/K mol ln 3.20/1.25=24.942* 0.94=23.44J/K

work done by the system=w=23.44J/K(energy leaves the system)

work done on the system=-23.44J/K

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