A mixture of n-hexane vapor and air leaves a solvent recovery unit and flows through a 70-cm diameter duct at a velocity of 3.00 mls. At a sampling point in the duct the temperature is 40C, the pressure is 850 mm Hg, and the dew point of the sampled gas is 25C. The gas is fed to a condenser in which it is cooled at constant pressure, condensing 60% of the hexane in the feed. (a) Perform a degree-of-freedom analysis to show that enough information is available to calculate the required condenser outlet temperature CC) and cooling rate (kW). (b) Perform the calculations. (c) If the feed duct diameter were 35 cm for the same molar flow rate of the feed gas, what would the gas velocity be?
Spencer Kociba CHEM 101 Lecture 11/15/16 THERMOCHEMISTRY ● Enthalpy ○ Represented as ΔH ○ Internal energy + pressure*volume ■ We will mostly be concerned with constant pressure. This is where the formula ΔH = ΔE + PΔV comes from ○ ΔH = q (enthalpy=heat gained or lost in the system) ● Properties of Enthalpy (ΔH ) ○ ΔH is directly proportional to mass ○ ΔH for a reverse reaction is equal in magnitude (quantity) but opposite in sign for the forwards reaction ○ Hess’s Law: ΔH is independent of the number of steps involved ■ If Reaction(1) + Reaction(2)=Reaction(3), then ΔH =3ΔH + 1H 2 ● Endothermic reactions ○ Gains heat from sur