Engineering chemistry I.B.tech mechanical engineering branch Important questions (internal and External exams)

UNIT – I  

1. a)   Distinguish between temporary and permanent hardness of waterb. Explain the EDTA method for the estimation of temporary hardness of water.c. 2 liters of water obtained from a bore well in Patencheru near Hyderabad gave the following analysis for salts.  FeSo4 =30.4mg, CaSo4=13.6mg, MgCl2=38mg, Ca(HCo3)2=32.4 , mg(HCo3)2=14.6mg, NaCl=11.7mg. Find the total hardness of water in ppm units, giving temporary &permanent hardness assuming the at. Mass of Fe=56, Ca=40, Mg=24, Na=22.2.     Write a brief account of:a)       Determination of chlorides in water.b)       Determination of dissolved oxygen in water.  3. Define Disinfection? What is its significance? Explain the        different methods used for disinfection of surface water.4. Explain the sedimentation process for the treatment of municipal water.  Define Temporary & permanent hardness of water & give an account of disadvantages & units.

UNIT-2

1. Write a brief account of lime soda process. 2. Write a brief account of internal treatment of water. 3. Write a brief account of Zeolite process. 4. Write a brief account of Ion exchange process. 5. Write a comparative statement on lime soda & Zeolite process. 6. What are Boiler troubles? Write short notes on scale & sludge formation and

caustic embrittlement ? 7. Calculate the lime and soda needed for softening 50,000 litres of water containing

the following salts: CaSO4 = 136 mg/lit; MgCl2 = 95 mg/lit; Mg(HCO3)2 = 73 mg/lit; Ca(HCO3)2= 162 mg/lit. Given that the molar mass of Ca(HCO3)2 is 162 and that of MgCl2 is 95

8. Determine the amount of soda and lime required in Kg’s to soften 5000 lit of water containing the following salts MgCl2 = 15.5 ppm, Ca(Hco3)2 = 32.5 ppm, Ca(No3)2 = 22.4 ppm, NaCl = 50 ppm, KCl = 22.5 ppm.

9. Calculate the quantities of lime and soda required in kgs for softening 10,000 lit of water using 82 ppm of NaAlO2 as coagulant. Analysis of water was as follows:Cacl2 = 111 ppm; Mg(HCO3)2 = 146ppm; NaCl = 58.5ppm; KCl = 74.5ppm; Dissolved CO2 = 44ppm. (At. Wt of  Na = 23, Mg = 24, K = 39, Ca = 40 and Al = 27)

UNIT-3

1.                  Explain the process of wet corrosion by evolution of hydrogen and                                    absorption of oxygen (or) Describe the electrochemical theory of corrosion.

2.                  Define corrosion? Write about rusting of iron based on electrochemical theory of corrosion and corrosion how is it different from erosion?3.                  Define corrosion? Explain any 4 factors that affect the rate of corrosion & explain any 4 corrosion control methods.4.                                      Write a short note on Inhibitors & Cathode protection.5.                                      Explain pitting and stress corrosion

UNIT-4

1.   Write a short note on a) Tining b) Metal cladding c) Electroplating                     2.    Write a short note on a) Sheradizing b) Chromising c) Colorizing3. Write a short note on anodizing & galvanizing.4. To write about surface preparations.5. Define paints. To write about paints constitution and their functions. 

UNIT-5

1. Identify the thermosets & thermoplasts among the following: PVC, polyethylene, silicon, polyester fiber, bakelite. What is Bakelite? How is it manufactured and mention its uses.

2.                  Write the differences between a) compression-Injection moulding   b) Additional polymerization-condensation polymerization      c) thermoset-thermoplasts.

3.                  Describe the manufacture , properties ,uses of  a)polyethylene

                                                                                 b) Teflon c) Thiokol       d) PVC

4. Write a short note on rubber and vulcanization. Write a brief account of elastomers, silicons.

5. Write preparation, properties and uses of nylon, polyester, and polyurethanes.

UNIT-6

1.                  What are Refractories? Explain thermal-spalling, porosity, & strength of refractories.

2.                  What are electrical insulators? Discuss their characteristics & engineering applications.

3.                  What are thermal insulators? Discuss their engineering applications and characteristics.

 

UNIT-7

 1. Explain the mechanism of lubricants: a) Boundary lubricants

                 b) Extreme pressure lubricants c) Thick film lubricants

                                                              .

2. Write a note on lubricants with special reference to their classification, mode of action, examples and uses.

3. Explain properties of lubricants: a) Flash &fire part b) Aniline point c) Cloud & pour point

d) Mechanical strength e) Viscosity and viscosity index                                                  4. Discuss the important functions of lubricants. Discuss solid & liquid lubricants

 

UNIT-8

1. (a) How calorific value of a gaseous fuel is determined by Junker’s gas calorimeter.Describe the experiment with a neat diagram . (b) Calculate gross and net calorific value of a gaseous fuel from the following data. Vol of gaseous fuel burnt at STP- 0.09m3, wt of water used for cooling 25.0 kg, Temp of inlet water 250C, temp of out let water 30.00C wt of water produced by steam condensation 0.02 kg latent heat of steam 587 Kcal/kg.[8+8]

2. Describe the manufacture of metallurgical coke by Beehive oven process. b)  What is thermal cracking?  Describe fixed bed catalytic cracking.

3. A)    With a neat diagram describe the orsat gas analysis method . What are the special precaution to be taken in the measurement .           

   b)       Define calorific values of a fuel. Distinguish  gross and net calorific value.

 

4. a)     Differentiate between proximate and ultimate analysis. b)           Calculate in calorific value of a fuel coal sample having composition? C-80%, H-3.5%, N-1.5%, Ash-7.2%

(a) What is knocking? What are its adverse effects? How it is prevented?(b) Define Octane and cetane Number. Explain how it can be improved. [8+8] 5. (a) How is coal is graded? Explain what is calorific value of coal. (b) Give the advantages and disadvantages of Coal over gaseous fuels. [8+8] 6. a) What are the Constituents of petroleum? Describe the Origin of petroleum. (b) Give an account of production of petrol from crude oil. [8+8] 7. (a) The analysis of a gas has the following composition . H2=14%, CH4 = 2%,CO=22%, CO2=5%, N2= 55%, O2= 2% . Find the air required for the complete combustion of 1m3 of the gas. If 45% excess air is supplied, find the volume analysis of the products. (b) A boiler is fired with coal having the following percentage composition by weight C=74%, H2 =6.8%, O2 =13.2% N2=2.1% S= 1.0% ash=2.9%. Calcu- late the minimum quantity of air required for the complete combustion of 1 kg of coal and the percentage composition of the dry product of combustion, if 20% excess air is supplied. [8+8] 8. (a) Explain Higher Calorific Value and Lower Calorific Value and distinguish the both.

(b) What are the characteristics of a good fuel? [8+8