Chemical Engineering Answers

what is the difference between chemistry and chemical engineering

. A magnetic stirrer agitated vessel is used for absorption of CO2 in water at 298 K and 2

atm pressure. Water is fed at a rate of 1 L/min and the carbonated water leaves the vessel

continuously so that a constant volume is maintained in the contactor. The outlet water

contains 2.3 g CO2/L. The interfacial area of gas-liquid contact is 80 m2

/ m3

; the volume of

gas-liquid dispersion is 8 L. The solubility of CO2 in water can be found using Henry’s law.

At 298 K, the Henry’s law constant for CO2 is 1640 atm/mole fraction and it’s diffusivity in

water is 1.92 x 10-9 m/s. The density of liquid is 997 kg/ m3

. Calculate:

(i) The thickness of the liquid film, if the Film theory is applicable.

(ii) The contact time between the liquid element with the gas if the Penetration theory is

applicable.

(iii) The surface renewal rate if the Surface-renwal theory is applicable. (

For the absorption of dilute gas mixture in a packed column, derive that

y y lm

y y

N

e

toG







1 2

In the Danckwerts model, it is assumed that elements of the surface have an age

distribution ranging from zero to infinity. Obtain the age distribution function for this model

and apply it to obtain the average mass transfer coefficient at the surface, given that from the

penetration theory the mass transfer coefficient for the surface of age θ is

/( ) DAB

. (4)

By what percentage would the rate of absorption be increased or decreased by increasing

the total pressure from 100 to 200 kN/m2

in absorption of ammonia from a mixture of

ammonia and air containing 10% ammonia by volume, using pure water as solvent. Assume

that all the resistance to mass transfer lies within the gas phase. The diffusivity can be

assumed to be inversely proportion to the absolute pressure.

Ammonia is diffusing through a non-diffusing gas mixture of methane and hydrogen in

volume ratio 2:1 under steady state condition. The total pressure is 1 atm. and the temperature

is 100C. The partial pressure of ammonia at two planes 2 mm apart is 13000 and 6500 N/m2

,

respectively. Calculate the flux of ammonia through the layer. Estimate also the quantity of

ammonia diffusing in kg/ day, if the area of cross section of stagnant gas film is 2 m2

.

NH 3 H 2

D  = 7.0 x 10-5 m

2

/ s at 303 K and 1 atm.

NH 3 CH 4

D  = 2.0 x 10-5 m

2

/ s at 288 K and 1.5 atm. (

If the hydrometer is to be constructed with a cylindrical floating rod. Nine fiduciary marks are to be placed along the rod to indicate densities of 0.98 g/cm3, 1.00 g/cm3, 1.02 g/cm3, 1.04 g/cm3, . . . 1.14 g/cm3. The row of marks is to start 0.200 cm from the top end of the rod and end 1.80 cm from the top end. Determine: (2.2) The required length of the rod; (2.3) The average density? (2.4) Should the marks be equally spaced? Explain your answer.

30,000 kg/h of n- butyl alcohol at 99oC is to be cooled to 40oC using water from 35oC to 46oC. Available for the service, is a 1-2 exchanger 48.9 cm I.D. shell with 204 tubes 19.05 mm O.D., 15.75mm ID, 4.88m long arranged on 2.54 cm square pitch. Vertically cut baffles are spaced 12.7 cm apart. Pressure drops of 0.7 kg/cm2 are allowable for both the tube and the shell sides. Find the dirt factor and test the suitability of the unit. Properties Cp (kcal/kg oC) µ , cp n- butyl alcohol at 69.5oC 0.7 0.91 k kcal/ kg m hr 0.142 Water at 40.5oC 1.0 0.70 0.543

Gaseous A absorbs and reacts with B in liquid according to

A(g) + B(1) R(I). -TA-KCACB

S. No.

k, m² liquid/mol hr H. Pa m' liquid/mol

HX

in a packed bed under conditions where

1

2

10⁰

10.

10⁰

10⁰

ka=0.1 mol/hr-m² of reactor - Pa

f₁ = 0.01 m³ liquid/m³ reactor

DA P=10 m³/hr

3

10

10³

ka = 100 m² liquid/m² reactor hr

a = 100 m²/m³ reactor

st 4

10

1

5

10-2

1

At a point in the reactor where p = 100 Pa and C₁ = 100 mol/m³ liquid

9

108

(a) calculate the rate of reaction in mol/hr-m¹ of reactor.

(b) describe the following characteristics of the kinetics:

location of the major resistance (gas film, liquid film, main body of liquid)

behavior in the liquid film (pseudo first-order reaction, instantaneous. second-order reaction, physical transport) for the following values of reaction rate and Henry's law constant.

A solid catalyzed gaseous reaction has the form A + B ↔ C (6) assuming the operating condition of the catalyst is such that the external and internal diffusion steps have negligible pressure gradients, propose rate equations for the following cases: (a) The adsorption of A on the catalyst is controlling (b) The surface interaction between adsorbed A and adsorbed B is controlling (c) The desorption of C from the surface is controlling