JNTU exam papers B -Tech I Semester Supplimentary Examinations, Chemical process calculations – November 2008

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


(Chemical Engineering)




1. A natural gas has the following composition on volume basis CH4-83.5%,C2H2 -9%

and N2-7.5%. Calculate:

(a) composition in mole %.

(b) the composition in weight %,

(c) average molecular weight of the gas and

(d) specific gravity of the mixture.


2. A natural gas has the following composition by volume CH4: 94.1%; C2H6: 3.0%

and N2 2.9% This gas is piped from the well at a temperature of 270C and an absolute pressure of 3.4 atm. It may be assumed that the ideal gas law is applicable,


(a) Partial pressure of the nitrogen

(b) Pure component volume of nitrogen per 100 m3 of gas Density of the mixture in kgs per m3 at the existing conditions


3. (a) Derive the Clausius-Claperyon equation State necessary assumptions to solve the problem.

(b) Calculate the vapor pressure at 25oC of a substance (mol.wt. 58) when its vapor pressure at 0oC is 180 mmHg and latent hate of vaporization is 90 cal per gram at 00C.


4. Air at a temperature of 200C and pressure 750 mm Hg has a relative humidity of 80%

(a) Calculate the molal humidity of air.

(b) Calculate the humidity of this air if its temperature is reduced to 100C and its pressure increased to 2.38 atm, condensing out some of the water.

(c) Calculate the weight of water condensed from 28 m3 of gas.

(d) Calculate the final volume of wet air leaving. Data: Vapor pressure of H2O at 200C is 17.5 mm Hg and at 100C is 9.2 mm Hg.


5. (a) A cotton mill dries a water soaked fabric in a drier from 54% to 9% moisture.

How many kg of water are removed by drying operation per 1200 kg of feed.


(b) A gas containing 2% NH3, 25.4% N2 and the rest H2 is flowing in a pipe. To measure the flow rate an ammonia rich gas containing 96% NH3, 3% H2 and 1% N2 is sent at a rate of 100 cc/min. The concentration of NH3 in the down stream is 6%. Find the flow rate of gas at inlet.


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:






7. Calculate the enthalpy of zinc vapor at 1000 0C and atmospheric pressure, relative

to the solid at 0 0C.Zinc melts at 419 0C and boils under atmospheric pressure at 907 0C. The mean specific heat of solid and liquid is 0.105 and 0.109 respectively.

The heat of fusion is 1660 cal per gm atom. Molal heat capacity of zinc is equal to 4.97 cal per gm mole.


8. The Orsat analysis of the flue gases from a boiler house chimney gives carbon di

oxide = 11.4% ; Oxygen = 4.2% ; and nitrogen = 84.4% (mole%). Assuming that

complete combustion has taken place,

(a) Calculate the % excess air, and

(b) find the C:H ratio in the fuel.

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