All Free Chemical Engineering MCQs with Answers

• A. Act as an acidifying agent
• B. Increase its concentration
• C. Increase the amount of molasses
• D. Increase the crystal size

Explanation: Sulfur dioxide dissolves in sugar juice and forms sulfurous acid, lowering the pH and helping clarify and preserve the juice.

• A. Furnace → evaporator → absorber
• B. Furnace → converter → absorber
• C. Furnace → converter → evaporator
• D. Converter → furnace → absorber

Explanation: Sulfur is first burned in a furnace to produce SO₂, which is oxidized to SO₃ in the converter and then absorbed to form sulfuric acid.

• A. As an illuminant
• B. For metal cutting/welding
• C. Both A. & B.
• D. Neither A. nor B.

Explanation: Calcium carbide reacts with water to produce acetylene, a highly combustible gas.

• A. Catalytic dehydrogenation of ethyl benzene
• B. Dehydration of ethyl alcohol followed by hydrogenation
• C. Reacting ethylene oxide with acetaldehyde
• D. Fermentation of starch

Explanation: Commercial styrene is made mainly by catalytic dehydrogenation of ethylbenzene, removing hydrogen from the ethyl side chain to form the…

• A. Act as optical brightening agent
• B. Prevent redeposition of soil on cleaned surface
• C. Inhibit corrosion in washing machines made of aluminium
• D. None of these

Explanation: CMC keeps loosened soil particles dispersed in the wash liquor, preventing them from settling back onto the cleaned fabric.

• A. Bauxite
• B. Boron carbide
• C. Silicon carbide
• D. Calcium carbide

Explanation: Carborundum is the commercial name for silicon carbide, SiC, a very hard abrasive material.

• A. Hard water contains sulphate
• B. They attract back the removed dirt
• C. They form insoluble calcium soaps which precipitate
• D. None of these

Explanation: Calcium and magnesium ions in hard water react with soap to form insoluble salts, commonly called soap scum, which precipitate instead of…

• A. 800
• B. 1600
• C. 4000
• D. 8500

Explanation: The turbidimetric fineness value quoted for ordinary cement is about 1600 cm²/g.

• A. Medicated
• B. Shaving
• C. Metallic
• D. Transparent

Explanation: Phenolic antiseptics are incorporated into medicated soaps to provide germicidal action during washing.

• A. Na2CO3
• B. NaHCO3
• C. Na2CO3.H2O
• D. Na2CO3.10H2O

Explanation: Baking soda is sodium hydrogen carbonate, NaHCO₃. Na₂CO₃ is washing soda in its anhydrous form, while Na₂CO₃·10H₂O is washing soda crystals.

• A. All A, B. and C
• B. Silver
• C. Copper
• D. Aluminium

Explanation: Aluminium is extracted electrolytically from alumina dissolved in molten cryolite in the Hall-Héroult process.

• A. Hydrogenation
• B. Hydrolysis
• C. Hydrocracking
• D. Hydration

Explanation: Hydrogenation adds hydrogen across the unsaturated bonds of vegetable oils, converting them into more saturated, solid fats.

• A. Hydrogenation
• B. Dehydration
• C. Hydration
• D. None of these

Explanation: Quicklime is calcium oxide, and adding water converts it to calcium hydroxide, or slaked lime: CaO + H₂O → Ca(OH)₂.

• A. Remove residual turbidity
• B. Reduce the bacterial load on filter
• C. Control taste and odour
• D. Remove chlorinous taste

Explanation: Dechlorination removes excess residual chlorine from treated water, especially to eliminate its characteristic chlorinous taste.

• A. 0.6
• B. 1.2
• C. 2.2
• D. 3.8

Explanation: Limestone supplies most of the calcium oxide in cement, but part of its mass is lost as carbon dioxide during calcination.

• A. Cellulose
• B. None of these
• C. Pentogens
• D. Lignin

Explanation: Bagasse fibre contains cellulose, lignin, and pentosans, so none of the listed substances is absent.

• A. Anthracene
• B. Creosote oil
• C. None of these
• D. Carbolic oil

Explanation: Anthracene, creosote oil, and carbolic oil are all fractions or products obtained from coal-tar distillation.

• A. All A , B., and C.
• B. Trinitrotoluene (TNT)
• C. Cellulose nitrate
• D. Nitro-glycerine

Explanation: Nitroglycerine, TNT, and cellulose nitrate are all explosive materials.

• A. Air
• B. Water
• C. Nitrogen
• D. Helium

Explanation: Yellow phosphorus is kept under water because it ignites readily in contact with air.

• A. lasting property
• B. Soft potassium soaps (potassium salt of fatty acid) with free Stearic acid to give lather a
• C. Metallic soaps compounded with frothing agents
• D. High free alkali soaps having excess of cane sugar and alcohol
• E. None of these

Explanation: Shaving soaps are soft potassium soaps, commonly containing free stearic acid.