Tuesday, April 11, 2006
HW #4 - P #7 - 1st Law Applied to Cooking an Egg
An ordinary egg can be approximated as a 5.5-cm-diameter sphere. The egg is initially at a uniform temperature of 8°C and is dropped into boiling water at 97°C. Taking the properties of the egg to be = 1020 kg/m3 and cP = 3.32 kJ/kg · °C, determine how much heat is transferred to the egg by the time the average temperature of the egg rises to 80°C.
Subscribe to:
Post Comments (Atom)
6 comments:
Am i doing this right? I am calculating enthalpy by integrating Cp-R but I can't find an R to use cause it needs to be in Kj/ mol something or other but we dont know the molar mass of the egg.
Anon 11:08
The change in enthalpy is the integral of Cp dT and Cp is given in the problem. So, you don't use R and you don't need to know MW of the egg.
In this problem I believe that deltaH = deltaU. I think this is because the process is both isobaric and isochoric. Is this true? Will deltaH always be equal to deltaU for all isobaric and isocholoric processes?
thank you
Anon 2:20
Yes. dU = dH for solids and incompressible liquids because whether the pressure remains constant or not, the specific volume does not change.
Good work.
thank you
Anon 6:12 PM
You are most welcome...and most polite too !
Post a Comment