JNTU II B-Tech I Semester Supplimentary Examinations,Chemical Process Calculations November 2008


JNTU II B.Tech I Semester Supplimentary Examinations, November 2008

Chemical Process Calculations

(Chemical Engineering) SET-2


1. A natural gas has the following composition, all figures being in volumetric percent:

Methane CH4 —83.5%. Ethane C2H6—-12.5% Nitrogen N2——4.0% Calculate:

(a) Composition in mole percent

(b) Composition in weight percent:

(c) Average molecular weight

(d) Density at standard conditions as pounds per cubic feet


2. (a) A gas mixture contains 0.1234 kg-mole of HCl ,0.153Kg-mole of nitrogen, and

0.04037 Kg-mole of oxygen .Calculate its density in kg/m3 at a pressure of 1.72 atm and a temperature of 400C

(b) State and prove law of Amagat


3. Hexane and heptane form ideal solutions. The following table gives the vapor pressure of hexane and heptane.


Temperature.(OC)     69     70      75       80       85        90       95       99.2

Hexane (mmHg)      760    780   915    1060   1125    1405    1577    1765

Heptane (mmHg)     295    302   348     426     498      588      675      760

Plot T-x-y and x-y diagram at 760 mmHg. Where T is the temperature, x is the

liquid phase mole fraction and y is vapor phase mole fraction.

Solve this problem graphically.


4. (a) If the atmosphere in the afternoon during a humid period is at 320C and 80

% RH (barometer reads 7.38 mm Hg) while at night it is at 200C (barometer reads 745 mm Hg), what percent of the water in the afternoon air is deposited as dew at night?

(b) By absorption in silica gel you are able to remove all (0.93 kg) of the H2O from moist air at 150C and 98.6 kPa. The same air measures 1000 m3 at 200C and 108.0 kPa when dry. What was the relative humidity of the moist air?



5. A laundry can purchase soap containing 30% water at the rate of Rs. 7 per 100 kg

f.o.b the factory. The same manufacturer offers another soap having 5% water. If the freight rate is Rs. 0.6 per 100 kg of soap what is the maximum price that the laundry should pay the manufacturer for the soap with 5% water ?(f.o.b.: freight on board)


6. (a) A solution of sodium chloride in water is saturated at a temperature of 150C.

Calculate the weight of NaCl that can be dissolved by 100 kg of this solution

if it is heated to 650C.

(b) Define the following terms: [16]





7. A solution containing 3kg salt per 100kg solution is evaporated to 15% in an evap-

orator. The heat capacity of the solution is 0.98 kcal/kg0C and that of the 15%

solution is 0.9. The feed temperature is 200C .Boiling point in the evaporator is

1040C. It requires 540 kcal to evaporate 1kg of water from the boiling solution. The

steam gives up only its latent heat of vaporization, 525 Kcal/kg. Calculate the kg

steam required per kg of feed..


8. Write short notes on

(a) Standard heat of reaction

(b) Standard heat of formation.


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