CHE 205

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# CHE 205 - PowerPoint PPT Presentation

CHE 205. Energy Balances. Vapor/Liquid Equilibrium. Multiphase Systems. Nonreactive Processes. \$200. \$200. \$200. \$200. \$400. \$400. \$400. \$400. \$600. \$600. \$600. \$600. \$800. \$800. \$800. \$800. \$1000. \$1000. \$1000. \$1000.

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Energy Balances

Vapor/Liquid Equilibrium

Multiphase Systems

Nonreactive Processes

\$200

\$200

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\$600

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What can you say about the bubble point and dew point temperatures of a mixture of two components A and B (T⁰b,A < T⁰b,B)? What about the compositions of the first bubble and last drop of mixture?

Draw the temperature plot for heating pure cyclohexane from 20 C to 100 C at a pressure of 1 atm. State what is happening in each region of the curve.

Write the equations to solve for the temperature and composition of a liquid in equilibrium with a vapor that is 30 mole% acetone-70 mole% ethanol at 1 atm. Is this a bubble-point or dew-point calculation? List vapor pressures as a variable and state where you would find them.

What can you say about the enthalpy of a system of air at 600 ⁰F and 1 atm? The value given in Table B.9 is 3719 BTU/lbmol

Cancel the terms of the energy balance of the following system and explain if the remaining terms are positive or negative

m2 kg H2O (v)/hr

P = 40 bar, sat’d

Isothermal

Condenser

m1 kg H2O (v)/hr

P = 20 bar

T = 250 C

m3 kg H2O (l)/hr

DAILY

DOUBLE

One thousand kilograms per hour of steam drives a turbine. The steam enters the turbine at 60 bar and 450C. The turbine delivers shaft work at a rate of 70 kW and the heat loss is 20 kW. Calculate the final temperature of the steam if the final pressure is 0.5 bar.

If a pump is 70 % efficient, how many kW are necessary to pump water flowing at 10 kg/s from a lake at 1 bar to an outlet 75 m above the lake at 5 bar, if the outlet pipe has a 4 cm ID?

Without using your book, what is the definition of bubble-point and dew-point temperatures? What assumptions must be made to apply Raoult’s or Henry’s Laws?

What is the dew point and composition of a mixture of 70% 1-propanol with the rest 1-pentanol in the vapor phase?

Given the following Txy diagram for styrene in toluene at 1000 mm Hg, if a mixture with 40 mole% of styrene is fed to an evaporator what is the bubble-point temperature and the equilibrium vapor composition?

A gas containing O2 is in equilibrium with liquid water containing a small amount of O2 at 30C and 3 atm. Would you use Raoult’s Law or Henry’s Law to estimate the relationship between

• xO2 and pO2
• xH2O and pH2O
• and why?

If HCN is taken from 25°C to 100°C, both states at 1 atm, but was carried out in such a way that the pressure varied during the heating, can you still use Cp to calculate the specific enthalpy and why?

• N2 (25°C to 700°C)
• H2 (800°F to 225°F)

Draw the process path of n-pentane going from a solid at -150°C and 0.5 atm to a vapor at 100°C and 4.0 atm. List where you would find the information to calculate ΔH for each step, but don’t calculate any of them.

DAILY

DOUBLE

Suppose the formula

• was used to calculate the specific enthalpy change for a change in temperature and pressure for
• An ideal gas
• A highly nonideal gas
• A liquid
• For which situation is the formula exact and which would have error?