Question
Carbon dioxide has no liquid phase at normal pressure ;it sublimates rather than melts , going directly from the solidfor, ( dry ice) to a vapor . This sublimation occurs at -78.5degree celcius with a heat of sublimation of 573100 j /kg. a) Draw the phase diagram (T vs Q) for a 1 kg sample of carbondioxide that covers the temperature range from -125 degree celsiusto - 25 degree celsius. the specific heat fo solide dry iceis 815 j/kg degree celsius and for the vapor is 2 j/kg Cdegree Carbon dioxide has no liquid phase at normal pressure ;it sublimates rather than melts , going directly from the solidfor, ( dry ice) to a vapor . This sublimation occurs at -78.5degree celcius with a heat of sublimation of 573100 j /kg. a) Draw the phase diagram (T vs Q) for a 1 kg sample of carbondioxide that covers the temperature range from -125 degree celsiusto - 25 degree celsius. the specific heat fo solide dry iceis 815 j/kg degree celsius and for the vapor is 2 j/kg Cdegree
Explanation / Answer
a)The energy released when 1 kg carbon dioxide sublimatesis Q = 573100 J/kg the energy released for 1 kg carbon dioxide is Q = 573100 J/kg * 1 kg = 573100 J the energy released when the solid form of carbon dioxide isconverted to the vapor form is Q1 = m * s * t m = 1 kg s = 2 J/kg.oC t = (-25 - (-125) oC = 100oC or Q1 = 1 * 2 * 100 = 200 J the energy released when it is directly converted to thevapor is Q2 = m * Lv where Lv is the latent heat of vapourization andhas a value 815 J/kg.oC or Q2 = 1 * 815 = 815 J The phase diagram (T vs Q) for a 1 kg sample of carbon dioxidecan be obtained by plotting the values of Q,Q1 andQ2 for different values of temperature(xaxis) T1 = -78.5 oC,T2= -25 oC and T3 = 100oC where Lv is the latent heat of vapourization andhas a value 815 J/kg.oC or Q2 = 1 * 815 = 815 J The phase diagram (T vs Q) for a 1 kg sample of carbon dioxidecan be obtained by plotting the values of Q,Q1 andQ2 for different values of temperature(xaxis) T1 = -78.5 oC,T2= -25 oC and T3 = 100oC