Reaction Chemistry
Energy/Mass Balance
Diagrams and Separation
Grab Bag
100
1. Balance the following equation and report the stoichiometric coefficient of CO2. 2. Define what type of equation this is:
C4H8 + O2 → CO2 + H2O
1. 4, 2. combustion
100
The mechanical energy balance is defined as 
100
Your system is set at the pressure and temperature of the red star. If you rapidly decreased the temperature without changing the pressure, 1. which phase would you leave, 2. which phase would you enter, 3. what is the black point called?
1. Liquid Phase, 2. Solid Phase, 3. Triple Point
100
When is Henry’s Law a good approximation?
If a liquid solution contains a small amount of dissolved solute (xA -> 0), Henry’s Law may be a good approximation
200
30.0 mol/h of acetylene and 70.0 mol/h of hydrogen are fed to a reactor. The balanced equation for this reaction is C2H2 + 2H2 → C2H6. Calculate the fractional excess of H2 being fed.
0.167 excess
200
Reactants are continuously fed into a horizontal, cylindrical reactor from which products are extracted. Assume the reactor has no moving parts. What is the simplified energy balance for this system?
delta H(dot)+Ek(dot)=Q(dot)
200
Use the graph below for n-hexane + n-octane vapor-liquid equilibrium at 1.5 bar. 1. Describe the system in each region (below blue line, in between green and blue line, above green line). 2. What do the red and purple dots mean? 3. What are the compositions of the phases of the system at 120C?
1. Below the blue line: all liquid, above the green line: all vapor, in the middle: vapor-liquid equilibrium.
2. The red dot is the boiling point of octane, the purple dot is the boiling point of hexane.
3. The compositions are liquid: ~0.2 hexane, ~0.8 water and vapor: ~0.55 hexane, ~0.45 water.
200
Solve for the final velocity if initial velocity is 10m/s, delta P= 3 Pa, the liquid density is 1500 kg/m3, and delta z= - 20 m?
22.1 m/s
300
You have a reactor that is a plant, and the reaction is photosynthesis (6CO2 + 6H2O → C6H12O6 + 6O2). If you put in 5 kg of CO2, and 2 kg of CO2 emerges, what is the extent of reaction in moles? (use CO2 as a basis)
68 moles
300
A steam mixer has 2 input streams and one output stream. Input stream 1 carries in 1000 kg/hr of saturated steam with specific enthalpy 2600 kJ/kg. Input stream 2 carries super heated steam at 400 C. The output stream releases superheated steam with a specific enthalpy of 3000 kJ/kg. Determine the mass flow rates for Input stream 2 and the output stream.
Input 2: m2=1439 kg/hr, Output: m3=2439 kg/hr
300
Consider a simple system where Raoult’s Law applies. Scientists have set up the system in a way where the mole fraction of the solvent varies with time. We know that the derivative of the mole fraction function X(t) is equal to -0.15t, the initial mole fraction of the solvent is 0.9, and the vapor pressure of the pure solvent is held steady at 0.43 atm. What is the vapor pressure of the solution at t = 2 seconds?
Psolution(2) = 0.258 atm
300
Calculate the rate of heat input required to raise 200 kg of Cl2 from 300 °C to 450 °C.
5.51 kJ
400
Consider the reaction 2A + 3B -> C. If a stoichiometric ratio of reactants A and B are fed to a reactor with a 90% conversion of A, what is the mole fraction of product C in the outlet stream? (Hint: use extent of reaction)
0.643
400
400 L/h of a 50 mole% - 50 mole% mixture of propane and butane at 0 °C and 1.5 atm and 250 L/h of 25 mole% propane - 75% butane at 25 °C and 1.5 atm are mixed and heated at constant pressure to 227 °C. Assuming ideal gas behavior, what is the required heat input?
Q = 1007 kJ/h
400
For a gas-liquid system of water and nitrogen gas at equilibrium at 80 C, determine 1. the gas-phase composition and 2. total pressure if the liquid phase is 1 mole% N2 and 99 mole% H2O. H constant for N2 is 12.6E4 and the vapor pressure is 355.1 mmHg.
1. 1260.46 atm, 2. yH2O = 3.6e-4, yN2 = 0.99
400
You measure the pressure of gas being pulled through a line by a vacuum pump with an open-end mercury manometer and get a reading of 4 in. 1. What is the general manometer equation? 2. What is the gauge pressure of the gas in kPa? 3. What is the absolute pressure in torr if Patm is 38 in. Hg?
1. 
2. 13.5 kPa, 3. 863.6 torr
500
A first-order, gas-phase reaction A→2B is carried out isothermally in a constant-volume batch reactor. The initial pressure of the system is 2 atm, with pure A present initially. After 5 minutes, the pressure of the system is observed to be 3 atm.
For a first order reaction, assume x = P0(1 - e-kt), with t in minutes, and x being the change in pressure of the system.
1. Calculate the rate constant, k, for the reaction in units of min-1.
2. Determine the total pressure in the reactor at 10 minutes.
1. k = 0.14 min-1, 2. Ptot= 3.5 atm
500
Two streams are fed into a mixer, the first stream with temperature T1 and pressure P1 and the second stream with temperature T2 and pressure P2. A single stream exits the mixer with temperature T3 and pressure P3. Assume the mixing has no moving parts, negligible changes in kinetic and potential energy, and accomplishes adiabatic mixing. Also assume steady-state. If the molar flow rate n3(dot)=10 mol/min, what are the molar flow rates of the two input streams, n1(dot) and n2(dot)? (Use the fact that H(hat)(T1, P1)=2853.3 kJ/mol, H(hat)(T2, P2)=2675.9 kJ/mol, and H(hat)(T3, P3)=2780.3 kJ/mol in your solution.)
n1(dot)=5.89 mol/min, n2(dot)=4.11 mol/min.
500
You have a mixture that is 78 kg water and 12 kg acetone. If you add 30 kg MIBK, how many kg of water end up in each of the two phases after separation?
mwater,1 = 3.43 kg ; mwater,2 = 74.5 kg
500
A detergent solution with a specific gravity of 0.91 flows from a storage tank down to a washing machine that washes dirty bags. The liquid effluent from the machine is pumped through a filter to remove dirt, and the cleaned detergent is recycled back up to the storage tank. Detergent flows from the storage tank to the washing machine by gravity feed at a rate of 500 L/min. All pipes in the line have 3.0-cm inner diameters. Friction losses are negligible in the line from the tank to the washing machine when the is valve is fully opened, and F =74 J/kg in the return line (from washing machine to storage tank), which includes the pump and filter. The entire system is at atmospheric pressure and ambient temperature.
Calculate the value of the height H between the washing machine and the storage tank required to provide the desired flow rate of detergent into the washing machine when the valve is fully opened.
Suppose the pump has an efficiency of 70%; that is, it delivers 70% of its rated value as shaft work. What must the rated value (kW) of the pump be to return 500 L/min of detergent to the storage tank?
1. H =7.1 m, 2. 2.3 kW