A 2-kg mass of oxygen expands at a constant-pressure of 172 kPa in piston-cylinder system from a temperature of 32°C to a final temperature of 182°C. [ Oxygen Cp = 0.918 kJ/kg · K]
(a.) Compute heat required in kJ
(b.) Compute steady-flow work in kJ
(c.) Compute total change in Total enthalpy in kJ
Q=272.8kJW=−77.97kJΔH=272.8kJn=322000=62.5molP=172kPaT1=305KT2=455KV1=PnRT1=172×10362.5×8.314×305=0.9214m3V1V2=T1T20.9214V2=305455V2=1.3746m3Work=W=−Pext(V2−V1)=−172×103(PnRT2−PnRT1)=−nR(T2−T1)=−62.5×8.314(455−305)=−77943.75JΔE=ncvΔT=62.5×25×8.314×150=194.86kJ
According to the first law of thermodynamics.
ΔE=q+W194.86=q−77.94kJq=272.8kJΔH=ncpΔT=62.5×27×8.314×150J=272.8kJ
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