A container initially at 323 K is heated to a final temperature of 573 K. If the

Question

A container initially at 323 K is heated to a final temperature of 573 K. If the device contains a mixture of nitrogen and oxygen along with other minor products is approximated as "lab air," and frictional effects are neglected.

(a) if the system is in a rigid container, how much heat and work are required assuming the container is V = 0.05 m^3 and the initial pressure is 450 kPa for the most efficient manner of heating? Assume constant Cv, Cp and R

(b) suppose the cntainer has one wall which is able to expand (no movement restriction) what is the increase in the heat needed to accomplish the process? Use Po & Vo from part a.

(c) if the sliding container from b is placed in an environment at 450 kPa & 298 K what is the final volume, temperature & pressure of the containers contents?

Explanation / Answer

a)

mass of gas=P1V1/RT1=(450*10^30.05)/(287*323)=243 gm

Cv=kR/k-1=287/0.4=717.5J/K

Heat required=mCv(T2-T1)=0.243*717.5*(573-323)=43588.125 J

Work done=0 (No Volume Change)

b)

Cp=kR/k-1=1.4*287/0.4=1004.5 J/K

Heat required=mCv(T2-T1)=0.243*1004.5*(573-323)=61023.375 J

c)

Final Temperature= 298K

Final Pressure=450 kPa

Final Volume=P/mRT=450/(0.243*287*298)=0.0216 m^3

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