• A pub opens its door for business at 6:00 PM. From 6:00 P.M. to 8:00 P.M. 50 smokers in the pub smoke 2 cigarettes per hour and each cigarette emits 4mg formaldehyde. Fresh air is introduced into the pub @ 1,000 m3/hr. At 8:00 P.M. the number of smokers in the pub increases from 50 to 75 and as a result, the fresh air flow rate is increased from 1,000 m3/hr to 1,500 m3/hr to flush out the stale air. Assume that all smokers in the pub still smoke 2 cigarettes per hour, what is the formaldehyde concentration (ppmv) in the air inside the pub @ 9:00 P.M.?
• The air volume inside the pub is 1,000 m³,
• the air temperature inside the pub is 25^oC,
• the air pressure inside the pub is 1 atm,
• and formaldehyde is converted to carbon monoxide following a first-order reaction pathway with k = 0.4 1/hr.

Thermodynamics problem:

An engine operates on an air-standard Otto cycle. The pressure and temperature of the isentropic compression 100 kPa and 40 °C, respectively. The pressure at the end of compression is 2.0 MPa and the net work is 87,000 J/mol. Assume ideal air-standard cycle. Determine the following:

1. pressure, volume, and temperature at end of each step.
2. compression ratio.
3. heat input and heat rejected per mol of working fluid.
4. thermal efficiency of the cycle.

A cylinder contains 200 kg of carbon dioxide at 5 MPa and 25°C (TC=304.2K, Pc=72.8atm, w=0.225, M=44.10 kg/kmol). A second cylinder contains nitrogen at 7 MPa and 25° C (Tc=126.2K, Pc=33.5atm, w=0.040, M=28 kg/kmol). A third cylinder contains oxygen at 6 MPa and 25°C (Tc=154.6K, Pc=49.8atm, w=0.021, M=32 kg/kmol). All 3 cylinders are the same size. When the contents of all the cylinders are moved into a reactor at a temperature of 75°C, the pressure is 12 MPa. Using the law of corresponding states and the generalized compressibility chart, determine the volume (m³) of the reactor.

Despite hydrophobic recovery shortcomings, surface activation methods are widely used for rendering PDMS hydrophilic. Why?

In a wood drier, the hot air must contain at least 2% by wt. water to prevent the wood from drying too rapidly and splitting or warping. The original fresh air feed contains 1% by wt. water. Wood is dried from 20% to 5% by wt. water. The wet air leaving the dried contains 4% by wt. water. Calculate the amount of wet air that must be returned to the drier if 1000 kg/hr of wet wood is dried.

2. Tanabe-Sugano diagrams

The octahedral coordination complex [Cr(brap)6]3+ has a ΔO value of 18,000 cm-1 and a B of 600 cm-1. The d3 Tanabe Sugano diagram is shown below.

a) Determine the energy of all allowed transitions and the lowest energy forbidden transition in cm-1. Show your work. (10 pts)

b) Draw the corresponding absorbance spectrum representing the transitions determined in a). The spectrum must have wavelength in nm as x axis units and e as the y axis units. Label each transition with correct term labels. Hint: Approximate values of e are sufficient based on selection rules. (10 pts)

514/bonus: Determine the color of the [Cr(brap)6]3+ complex based on the lowest energy, allowed transition (5 pts)

An evil scientist has constructed a shaft that passes through the center of the Earth to the other side as a way of getting

rid of his rivals. If he drops a rival who is an average height and weight male into the shaft, predict how far they make

it to the surface on the other side of the core. Would they emerge on the other side of the Earth? If they do not, what

is the fractional distance back to the surface they would make it? The Earth’s diameter is 12.72 million meters.

Assume the shaft is at ambient temperature.

The flat iceberg drifts over the ocean, as it is driven by the wind that blow over the top. The iceberg may be modeled as a block of frozen fresh water at 0 oC. The temperature of surrounding sea water is 10 oC, and the relative velocity between it and iceberg is 10 cm/s. The length of iceberg in the direction of drift is L=100 m. The relative motion between the sea water and the flat bottom of the iceberg produce a boundary layer of length L. The 10 oC temperature difference across this boundary layer drives a certain heat flux into the bottom surface of the iceberg. This heating effect causes the steady erosion (thinning) of the flat piece of ice. If H(t) is the instantaneous high of the ice slab, calculate the ice melting rate dH/dt average over the swept length of the iceberg.

An isothermal CSTR is used for liquid phase reaction A+B→C+D, -ra=kC_a*C_b   and k=1x10^11 exp⁡((-36900)/2.74T) determine the residence time required for this reaction to achieve 60 % conversion of the limiting reagent and mole fraction of C. The feed to the reactor is 200 mol/min A and 150 mole/min of B with flow rate of 20 l/min. The inlet temperature is 497 K.

For the transfer function in question 4, use the Skogestad’s “Half Rule” method to find an approximate second-order-plus-time-delay model of the form Ke-θs/{(τ1s+1)(τ2s+1)} and determine the values of

a. ________

b. ________

c. ________

Q) Write the problems caused if an uncalibrated machine is used for some analysis?

Discuss why bulk micromachining of silicon could generate high-aspect ratio features (e.g. deep valleys) with well-defined side walls instead of undercutting into the material.

1. Write very briefly about the following:                                                                        

a)  Fick’s second law and its application

b) Different Mass transfer coefficients

c) Raoult’s law and Henry’s law and their applications  

d) Give the j_D correlation for mass transfer in flow parallel to flat plate

e)  Chilton – Colburn analogy

f) Capacity coefficients and their use

g) Marangony effect

2. Explain and derive the Mass transfer flux equation for molecular diffusion in gases for the case of (i) Equimolar counter diffusion and (ii) A is diffusing through stagnant non diffusing B.
3. a) Explain the diffusion through a varying cross sectional area and derive the equation for mass transfer flux.

        4)   a) Explain briefly about the diffusivities in gases

b) Explain briefly about the diffusivities in liquids

1. Explain the diffusivities of electrolytes in liquids              

b) Predict the diffusion coefficients of dilute electrolytes for the following cases:

i) For  KCl at 25 ⁰C, calculate  .

ii) For  KCl at 18.5 ⁰C, calculate  .             

iii) For  CaCl₂ at 25 ⁰C, calculate  . Also predict Di of ion Ca⁺² and of  Cl^-.

Data: λ₊(K⁺) =73.5, λ_-(Cl^-) =76.3, λ₊(Ca²⁺/2) = 59.5

       6)   Explain (a) The two film theory and (b) The penetration theory.                       

      7)   Explain the mass transfer in the laminar boundary layer when the fluid is in laminar flow over a flat plate.

8).Explain the following briefly.

1. Individual and overall mass transfer coefficients.
2. Reynolds analogy.   

A shell-and-tube heat exchanger is to used to heat water (in the tube side) from 30 deg C to 40 deg C at a mass flow rate of 4 kg/s. The fluid used for heating (shell side) is water entering at 90 deg C with a mass flow rate of 2 kg/s. A 1-2 STHE is used and the overall heat transfer coefficient based on the inside area is 1390 W/m2-K. The tubes are 1.875 in diameter (inside) and require an average velocity of 0.375 m/s.

What is the effective (corrected) temperature driving force in deg C?

a. 37
b. 35
c. 42
d. 30

How many tubes are available per pass?

a. 31
b. 20
c. 39
d. 43

What is the required heat transfer area in m2?

a. 4.2
b. 5.7
c. 4.8
d. 5.2

What length of pipe will be required to accomplish the desired heat transfer?

a. 1.12 m
b. 2.12 m
c. 1.79 m
d. 2.5 m