Question

SECTION C 5Seventy-five litres of liquid ethanol at 70°C and 55 L of liquid water at 20°C are mixed at constant pressure in a well-insulated flask. [1 mark] (a) Draw a flowchart of the flask. [2 marks] (b)Create the inlet-outlet enthalpy table for the flask. [3 marks] (c) Write the energy balance equation for the flask. (d)Using the following data for the liquid heat capacities of ethanol and water: Cp 103.1x10 kJ (mol. C) at 0 C Ethanol: Ср 158.8x 10% k/ /(mol. C) at 100 C Cp-75.4x10-3k/ /(mol. C) at 0-100°C Water: derive expressions for the specific enthalpies of the streams neglecting evaporation and the heat of mixing. Specific gravity of ethanol is 0.789 [4 marks] (e)Estimate the final mixture temperature [7 marks] (f)When the final temperature was measured, it did not equal the value estimated [3 marks] in part (e). List six reasons for that.

Answer 1

Ans- LiRud ethanol 구oc and 55L tiquid water at doc ae miaed Presume in αυ)디-insulated ⅓tagk tooo kam dersi tl ot ethanol-489 kgl㎡ | mizing Had Cm) Molan mass oh wateづ (m): 18. DtS3 glmbe so, her cp ot waとer = 15.dtpeto3 kr. X-レ nole ton) mblar ma o ethan) 67 glmole Hence h601163 kak h]小 cp 아 ethanol Qtoe ='588x 103 kT 46.01 xi63 g =3415 k

cpot ethanol at /3 dt 10o volume of ethanel 1s tre 15 xts3m 0.015m mase of ethanol 18x 075 meS9.11S volume or water =55 l:he SSS X103 ms mass water tooorooss Now, enti o ethandl at toc enthalpy o water at dec 59.115kg m, = @) Enthol Proce

14 ts usel solved in above pant o kind weber ; Fina tempesalure t31. 318k ( THere are olldwng easoni Neglected heat generation during miaim glected et evaporatron th Neg (ift) Atpnoti moted the cp ot esthand lineal V) As umed in sulted last, but in actual ease ↑tic not .