Code No:NR-210803

II B.Tech. I-Semester Supplementary Examinations, November-2003

MATERIAL AND ENERGY BALANCE (Chemical Engineering)

Time: 3hours Max.Marks:80Answer any FIVE questions

All questions carry equal marks ----

1.a) A cylinder contains 25 kg of liquid chlorine. What volume in cubic metre will the chlorine occupy if it is released and brought to standard conditions?

b) Gaseous propane C3H8 is to be liquefied for storage in steel cylinders. How many grams of liquid propane will be formed by the liquefaction of 500 litres of the gas, the volume being measured at standard conditions?

2. Calcium hypo chlorite is produced by absorbing chlorine in milk of lime. A gas produced by the deacon chlorine process enters the absorption apparatus at a pressure of 740 mm Hg and a temperature of 24C. The partial pressure of the chlorine is 59 mm Hg, the remainder being inert gases. The gas leaves the absorption apparatus at a temperature of 27C and a pressure of 743 mm Hg with a partial pressure of chlorine of 0.5 mm Hg. Calculate:

a) Volume of gases leaving the apparatus per 100 cu m entering. b) Weight of chlorine absorbed per 100 cu m of gas entering.

3.a) The vapor pressure of ethyl ether is given in the International Critical Tables as 185 mm Hg at 0C. The latent heat of vaporization is 92.5 cal per gram at 0C. Calculate the vapor pressure at 20 and 35C.

b) Explain the phenomenon of vaporization. Define vapor pressure of a liquid and discuss the effect of temperature on vapor pressure.

4.a) Define humidity, relative humidity, molar humidity, saturation humidity and percentage humidity.

b) By absorption in silica gel you are able to remove 0.93 kg of H2O from moist air at 15C and 98.6 kPa. The same air measures 1000 m3 at 20C and 108 kPa when dry. What was the relative humidity of moist air?

5.a) A mixture of CuSO4.5 H2O and FeSO4.7 H2O weighs 100g. It is heated in an oven at 1050C to evaporate the water of hydration. The weight of the mixture after the removal of all the water is 59.78g. Calculate the weight ratio of CuSO4 to FeSO4 in the mixture

b) Oxygen is mixed with air to produce an oxygen rich air containing 60 mole % Oxygen. In what ratio by weight oxygen and air are to be mixed?

(Contd..2)

Set No.

1

Code No:NR-210803 -2- Set No:1

6.a) Butane is burnt with 80% of the theoretical air. If all the hydrogen present in Butane gets converted to H2O find the complete analysis of the flue gas .

b) A coke contains 90% Carbon and 10% ash (by weight). If 50 % excess air is used calculate the analysis of the gases at the end of complete combustion .

7.a) State the principle behind energy balances and the basis used in establishing a general energy balance for any process.

b) Discuss about the separate forms of energy that are included in the general energy balance equation.

8.a) What is heat of formation? Explain b) On the basis of the data and the chemical reactions given below, find the heat of

formation of ZnSO4 from elements:Zn + S ZnS H = -602.5 kJ/kg mol2ZnS + 3O2 2ZnO + 2SO2 H = -928.3 kJ/kg mol2SO2 + O2 2SO3 H = -196.1 kJ/kg molZnO + SO3 ZnSO4 H = -230.5 kJ/kg mol

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Code No:NR-210803

II B.Tech. I-Semester Supplementary Examinations, November-2003

MATERIAL AND ENERGY BALANCE (Chemical Engineering)

Time: 3hours Max.Marks:80Answer any FIVE questions

All questions carry equal marks ----

1.a) Calculate the weight of iron and of steam required to produce 100 kg of hydrogen and the weight of the Fe3O4 formed. What volume will the hydrogen occupy at standard conditions?

3Fe+4H2OFe3O4+4H2 b) An aqueous solution contains 40% Na2CO3 by weight. Express the composition in mole

percent and in normality.

2.a) Calculate the number of cubic feet of hydrogen sulfide, measured at a temperature of 50C and a pressure of 740 mm Hg, which may be produced from 3.1752 kg of iron sulphide (FeS).

b) An automobile tire is inflated to a gage pressure of 2.38 atm at a temperature of 0F. Calculate the maximum temperature to which the tire may be heated without the gage pressure exceeding 3.4 atm. (Assume that the volume of the tire does not change.)

3.a) What are critical properties? Write about estimation of critical properties of organic substances and inorganic substances.

b) A mixture of ethyl acetate vapor and air has a relative saturation of 50% at 30C and a total pressure of 740 mm Hg. Calculate the analysis of vapor and percentage molar saturation, the vapor pressure of ethyl acetate at 30C is 119 mm Hg.

4. Nitrogen is saturated with benzene vapour at a temperature of 30C and a pressure of 720 mm Hg. Benzene exerts a vapor pressure of 118.5 mm Hg at 30C. Calculate the composition of the mixture expressed in the following terms:(a) Percentage by volume.(b) Percentage by weight.(c) kg of benzene per m3 of mixture.(d) kg of benzene per kg of nitrogen.(e) kg. mole of benzene per kg mole of nitrogen.

5.a) It is desired to make 1000kg of a mixed acid containing 60% H2SO4 , 32% HNO3 , and 8% water by blending (i) a spent acid containing 11.3% HNO3, 44.4% H2SO4 and 44.3% Water (ii) aqueous 90% HNO3 and (iii) aqueous 98%H2SO4 . All percentages are by weight. Calculate the quantities of each of the three acids required for blending

b) Explain the terms Bypass and Recycle

(Contd..2)

Set No.

2

Code No:NR-210803 -2- Set No:2

6.a) SO2 is oxidized to SO3. If the conversion is 70% and the air used is 80% excess over the theoretical requirement, calculate the composition of the gases leaving the reactor (on volume basis)

b) A gas analyzing CO2 5.5%, CO 25%, H2 14% CH4 0.5% and N2 55% by volume is burnt in a furnace with 10% excess air. Calculate the Orsat analysis of the flue gas.

7.a) How does the heat of vaporization of a substance vary with its temperature and pressure?b) The latent heat of vaporization of ethyl alcohol is experimentally found to be 204 cal per

gram at its normal boiling point of 78oC. Its critical temperature is 243oC. Estimate the heat of vaporization at a temperature of 180oC.

8.a) What is thermoneutrality of salt solutions? Explain with an example b) Discuss briefly about (i) heats of formation of ions

(ii) heats of formation of atoms.

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Code No:NR-210803

II B.Tech., I-Semester Supplementary Examinations, November-2003

MATERIAL AND ENERGY BALANCE (Chemical Engineering)

Time: 3hours Max.Marks:80Answer any FIVE questions

All questions carry equal marks ----

1.a) A solution of naphthalene C10H8 in benzene C6H6, contains 25 mole% of naphthalene. Express the composition of the solution in weight per cent and mole percent.

b) Write short notes on density, specific gravity.

2. A natural gas has the following composition by volume:CH4 94.1%, C2H6 3.0%, N2 2.9%.This gas is piped from the well at a temperature of 27C and an absolute pressure of 3.4 atm. It may be assumed that the ideal-gas law is applicable. Calculate:a) Partial pressure of the nitrogen.b) Pure-component volume of nitrogen per 100 cu m of gas.c) Density of the mixture in kgs per cubic meter at the existing conditions.

3.a) Calculate the total pressure and the composition of the vapors in contact with a solution at 100C containing 35% benzene (C6H6), 40% toluene (C6H5CH3), and 25% orthoxylene (C6H4(CH3)2) by weight. Vapor pressure at 100C: Benzene = 1340 mm Hg, Toluene = 560 mm Hg, o-Xylene = 210 mm Hg.

b) State the Raoults law. What are the assumptions made in writing this law.

4.a) Describe adiabatic vaporization with an example. What type of industrial operations are carried out using adiabatic vaporization ?

b) What is the minimum number of cubic meters of dry air at 20C and 100 kPa that are necessary to evaporate 6 kg of ethyl alcohol if the total pressure remains constant at 100 kPa ? Assume that the air is blown through the alcohol to evaporate it in such a way that the exit pressure of the air-alcohol mixture is at 100 kPa.Vapor pressure of ethyl alcohol at 20C =5.93 kPa.

5.a) What do you mean by the term unsteady state process?b) Two students are evaluating the average molecular weight of a gas mixture containing

Nitrogen and other gases. One of the students using the correct molecular weight of 28 for Nitrogen estimates the average molecular weight as 39.4. The other using an incorrect value of 14 estimates the average molecular weight as 33.8%. Calculate the weight percentage of Nitrogen in the mixture.

(Contd..2)

Set No.

3

Code No:NR-210803 -2- Set No:3

6. a) A produces has the following composition by percent at NTP:CO = 23.0%CO2 = 4.4%O2 = 2.6%N2 = 70.0%

Calculate the composition of gases leaving the burner assuming complete combustion when the gas is burnt with 20% excess of oxygen.

b) Pure methane is burnt completely to CO2 and water vapour in a furnace. Air is oxidizing agent and is supplied 50% extra. Calculate the amount of flue gases produced and the composition of gases by volume.

7.a) What is heat of vaporization? Explain.b) Discuss briefly about the various methods available for calculating heat of vaporization.

8.a) Explain heat of mixing with an example. b) The heat of mixing of water and glycerin to form a solution containing 40% glycerin is

18.828 J/g of solution. Calculate the integral heats of solution of glycerin and of water at this concentration.

c) Discuss about the heats of neutralization of acids and bases.

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Code No:NR-210803II B.Tech., I-Semester Supplementary Examinations, November-2003

MATERIAL AND ENERGY BALANCE

(Chemical Engineering)Time: 3hours Max.Marks:80

Answer any FIVE questionsAll questions carry equal marks

----1.a) Differentiate between density and specific gravity. b) Write about the following :

Specific gravity scales: Baume gravity scale, API scale, Twaddell scale.

2. A mixture of ammonia and air at a pressure of 730 mm of Hg and a temperature of 30C contains 5.1% NH3 by volume. The gas is passed at a rate of 0.0472 cu m per second through an absorption tower in which only ammonia is removed. The gases leave the tower at a pressure of 725 mm Hg, a temperature of 20C, and contain 0.05% NH3 by volume. Using the ideal-gas law, calculate:a) Rate of flow of gas leaving the tower in cubic meter per second.b) Weight of ammonia absorbed in the tower per second.

3.a) Estimate the heat of vaporization of isobutyric acid at 200oC. Data: vapour pressure data for isobutyric and are:

Pressure (atm) Temperature, oC2 179.85 217.0

Write down the assumptions involved in solving this example.

4. Air at 35 C, 1 atm and 32C wet bulb temperature is compressed to 197 atm and 40C. Calculate the actual amount of water condensed per 50 m3 of the original air.Data: Initial humidity = 0.029 kg water/kg dry air

Vapour pressure of water at 40C = 55.32 mm Hg

5.a) Discuss the usefulness of recycle and purge streamsb) An aqueous solution containing 33% by weight of of Na2SO4 is cooled to 200C when

Na2SO4. 10H2O crystallizes out. Calculate how much of the crystals that would be formed from a 100kg original solution. The solubility of Na2SO4.10H2O in water at 200C is 19.4 g/100 g water.

6. A coal containing 87% total carbon and 7% unoxidised hydrogen is burned in air.a) If air is used 40% in excess of that theoretically required, calculate the number of kgs of

air used per kg of coal burned.

Set No.

4

b) Calculate the composition, by weight, of the gases having the furnace, assuming complete combustion.

(Contd..2)Code No:NR-210803 -2- Set No:4

7.a) Define heat capacity and specific heat. b) Show that Cp = Cv + R c) Discuss about the effect of temperature and pressure on the heat capacity of gases.

8.a) Define theoretical flame temperature, maximum adiabatic flame temperature and actual flame temperature.

b) Calculate the theoretical flame temperature of a gas containing 20% CO and 80% N2 when burned with 100% excess air, both air and gas initially being at 25oC.The standard heat of reaction = -282.989 x 103 kJ /kg molThe mean heat capacities between 25 and 943oC are in kJ/kg mol K:CO2 = 49.45, O2 = 33.06, N2 = 31.25

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