Q: Hardness of a given water sample is 250 ppm. Express the hardness in degree C…

Hardness of 250 ppm is equivalent to $17.5^{\circ}\text{Clarke}$ and $25.0^{\circ}\text{French}$.

Question 1

Hardness of a given water sample is 250 ppm. Express the hardness in degree C…

Accepted Answer

Hardness of 250 ppm is equivalent to $17.5^{\circ}	ext{Clarke}$ and $25.0^{\circ}	ext{French}$.

Question 2

What do you understand by Break Point Chlorination.

Accepted Answer

Break Point Chlorination is the point at which enough chlorine has been added to water to satisfy all chlorine demand, leaving free residual chlorine.

Question 3

The Gross calorific value of a coal sample is 9650 kcal/kg. Calculate the Net…

Accepted Answer

The Net Calorific Value (NCV) of the coal sample is $9333.02 	ext{ kcal/kg}$.

Question 4

What is synthetic petrol? Name the two methods used to convert coal to gasoline.

Accepted Answer

Synthetic petrol is a liquid hydrocarbon fuel synthesized from solid coal or gaseous fuels. The two methods are Bergius process and Fischer-Tropsch process.

Question 5

Under identical conditions why does impure metal corrode faster than pure metal?

Accepted Answer

Impure metals corrode faster because the impurities act as cathodes, setting up numerous local galvanic cells that accelerate the oxidation of the anodic base metal.

Question 6

What is 'Flash set' of cement the name the compound responsibel for it.

Accepted Answer

Flash set is the sudden and premature stiffening of cement paste. It is caused primarily by Tricalcium Aluminate ($C_3A$).

Question 7

What do you understand by annealing of glass and what is its significance?

Accepted Answer

Annealing is the controlled slow cooling of glass to relieve internal stresses. It prevents spontaneous cracking and increases durability.

Question 8

What is Steam Emulsion Number of a lubricant?

Accepted Answer

Steam Emulsion Number (SEN) is the time required for an oil-water emulsion to separate into distinct layers when steam is passed through it.

Question 9

Why anodic coatings are better than cathodic coatings for corrosion control?

Accepted Answer

Anodic coatings protect the base metal sacrificially even if scratched, whereas cathodic coatings accelerate corrosion of the base metal if the coating breaks.

Question 10

What type of addition reactions occur in carbonyl compounds and why?

Accepted Answer

Carbonyl compounds undergo Nucleophilic Addition reactions because the polar nature of the $C=O$ bond leaves the carbon atom partially positive (electrophilic).

Question 11

Calculate the amount of lime and soda required to soften 10,000L of a water s…

Accepted Answer

To soften 10,000 L of water containing specific impurities, we convert all hardness-causing salts to their CaCO3 equivalents. Using standard lime and soda formulas, the calculated requirement is 0.37 kg of Lime and 0.318 kg of Soda.

Question 12

Define knocking. Explain the phenomenon of knocking in a petrol engine.

Accepted Answer

Knocking is the sharp, explosive, and spontaneous combustion of the unburnt air-fuel mixture ahead of the normal flame front in a spark-ignition engine. It drastically reduces efficiency and damages engine components.

Question 13

What is Pitting corrosion? Explain the mechanism.

Accepted Answer

Pitting corrosion is an extremely localized, intense, and destructive form of galvanic corrosion that creates deep cavities or holes in a metal. It is driven by the localized breakdown of a protective passive film in the presence of aggressive ions like chlorides.

Question 14

Define cloud and pour point of a lubricating oil. How can you determine the c…

Accepted Answer

Cloud point is the temperature at which dissolved waxes in oil crystallize to form a cloudy haze. Pour point is the lowest temperature at which the oil will still flow. Both are vital for assessing a lubricant's suitability for cold-weather operation.

Question 15

Describe the synthesis, properties and uses of Paracetamol.

Accepted Answer

Paracetamol (Acetaminophen) is a widely used, mild analgesic and antipyretic drug. It is synthesized industrially via the nitration of phenol, followed by reduction to p-aminophenol, and finally acetylation using acetic anhydride.

Question 16

Explain the following: 
(a) Role of gypsum in cement 
(b) Borosilicate glass

Accepted Answer

Gypsum acts as a vital chemical retarder in Portland cement, preventing the catastrophic 'flash set' caused by C3A. Borosilicate glass, enriched with silica and boron, possesses a remarkably low thermal expansion coefficient, making it highly resistant to extreme thermal shock.

Question 17

What is Proximate analysis of fuel and what is its significance?

Accepted Answer

Proximate analysis is an empirical procedure that determines the physical composition of coal by evaluating its moisture, volatile matter, ash, and fixed carbon content. It provides a rapid, practical assessment of a coal's commercial quality and suitability for specific industrial uses.

Question 18

(a) What do you understand by Priming and Foaming?
(b) 0.5g of $CaCO_{3}$ was…

Accepted Answer

Priming and foaming are dangerous boiler carry-over phenomena. EDTA titration calculates total, permanent, and temporary hardness. The calculated total hardness is 312.5 ppm, permanent is 208.33 ppm, and temporary is 104.17 ppm.

Question 19

(a) Explain the determination of calorific value of a fuel using a Bomb Calor…

Accepted Answer

The Bomb Calorimeter provides a highly precise measurement of the Gross Calorific Value (GCV) of solid and non-volatile liquid fuels by conducting combustion at a constant volume. The calculation dictates the fuel sample requires 11.51 kg of air per kg of coal.

Question 20

(a) Explain the mechanism of chemical (dry) corrosion.
(b) Explain the sacrif…

Accepted Answer

Corrosion severely impacts metal lifespan. Dry corrosion occurs by direct chemical attack, primarily oxidation, forming protective or non-protective scales. Sacrificial anodic protection involves coupling the structure to a more active metal like zinc, turning the entire structure into a protected cathode.

Question 21

Write short notes on: 
(a) Manufacture of cement by Rotary kiln method 
(b) C…

Accepted Answer

Cement is manufactured by high-temperature calcination in a rotary kiln to form clinkers, which are ground with gypsum. Lubricants reduce friction and wear between moving surfaces and are classified as liquid, semi-solid, or solid based on physical state.

Question 22

Explain the mechanism of: 
(a) Electrophilic aromatic substitution in benzene…

Accepted Answer

Electrophilic Aromatic Substitution (EAS) in benzene, such as nitration, proceeds via an arenium ion intermediate. SN1 reactions in tertiary alkyl halides, like t-butyl bromide, are two-step processes forming a planar carbocation, resulting in a racemic product.

Engineering Chemistry