Question 1

Pharmaceuticals: which of the following is a drug used in oral contraceptive formulations (as an estrogen component)?

Accepted Answer

Introduction: Combined oral contraceptives typically contain an estrogen and a progestin. Recognizing common active ingredients is important for pharmacy, medicine, and biotechnology students. Given Data / Assumptions: Mestranol is a synthetic estrogen (a prodrug of ethinyl estradiol). Other listed compounds have unrelated indications. Question asks specifically for a contraceptive drug. Concept / Approach: Estrogen components (e.g., mestranol, ethinyl estradiol) are combined with progestins (e.g., norethindrone, levonorgestrel) to suppress ovulation and alter the endometrium/cervical mucus. Antibiotics (penicillin), analgesic/liniment component (methyl salicylate), and antibacterial sulfonamide (sulphadiazine) are not used as contraceptives. Step-by-Step Solution: Identify estrogenic agent: mestranol.Exclude antibiotics/analgesics: not contraceptives.Select mestranol as correct contraceptive component. Verification / Alternative check: Drug compendia list mestranol–norethindrone as a historical combination; modern products often use ethinyl estradiol instead of mestranol but the classification remains valid. Why Other Options Are Wrong: Penicillin: antimicrobial, no contraceptive effect. Methyl salicylate: topical counterirritant. Sulphadiazine: antibacterial sulfonamide. Common Pitfalls: Assuming any hormone-like name is a contraceptive; only specific estrogens/progestins are used for this indication. Final Answer: Mestranol

Question 2

Water softening by the zeolite (sodium aluminosilicate) method: after exhaustion, the used zeolite bed is regenerated by flushing with a solution of which salt?

Accepted Answer

Introduction: Zeolite softeners exchange sodium ions for hardness-causing calcium and magnesium. Regeneration restores the sodium form of the zeolite for continued service—an essential concept in water treatment operations. Given Data / Assumptions: Zeolite (Na-form) exchanges Na+ for Ca2+/Mg2+. After exhaustion, zeolite is in Ca/Mg form. Regeneration uses a concentrated brine. Concept / Approach: Flushing with concentrated NaCl displaces Ca2+ and Mg2+ from the zeolite structure, reinstating Na+ on the exchange sites. Other salts listed either add hardness or do not effectively drive the exchange back to sodium form. Step-by-Step Solution: Identify exhausted state: zeolite-Ca/Mg.Apply regeneration: high [Na+] from brine (NaCl) shifts equilibrium to zeolite-Na.Rinse to remove displaced Ca/Mg chloride brine. Verification / Alternative check: Standard water softener operation manuals specify saturated or near-saturated NaCl brine for regeneration cycles. Why Other Options Are Wrong: Calcium sulphate / Magnesium chloride: would load more hardness. Sodium sulphate: weaker driving force and not standard practice for regeneration. Common Pitfalls: Confusing zeolite regeneration (NaCl) with ion-exchange deionization (acid/caustic) or lime–soda softening chemistry. Final Answer: Sodium chloride

Question 3

Water treatment: the process used to remove very fine suspended and colloidal impurities (that do not settle by plain sedimentation) is called

Accepted Answer

Introduction: Raw water frequently contains colloids and ultra-fine particles that remain stable and do not settle under gravity due to electrostatic repulsion and Brownian motion. This question targets the correct unit process to remove such fines. Given Data / Assumptions: Particles are too small to settle quickly by gravity. No membrane filtration is implied. Conventional clarification trains are considered. Concept / Approach: Coagulation neutralizes surface charges using coagulants (e.g., alum, ferric salts, polymers), destabilizing colloids. Flocculation then gently mixes to form larger, settleable flocs. Disinfection targets pathogens, not turbidity. Softening removes hardness ions rather than colloids. Simple sedimentation alone is ineffective for stable colloids. Step-by-Step Solution: Add coagulant to neutralize zeta potential.Induce flocculation to aggregate microflocs into macroflocs.Clarify by settling or dissolved air flotation, followed by filtration. Verification / Alternative check: Turbidity and true color reductions after coagulation–flocculation–sedimentation are standard performance indicators in water treatment plants. Why Other Options Are Wrong: Disinfection: microbial inactivation only. Softening: targets Ca2+/Mg2+, not colloids. Sedimentation only: insufficient for colloid removal without destabilization. Common Pitfalls: Overdosing coagulant can restabilize colloids; proper jar testing is essential to optimize dose and pH. Final Answer: Coagulation (often followed by flocculation)

Question 4

Cement technology: the raw mix used to produce which cement type is specifically formulated to avoid iron oxide so that a light color is obtained?

Accepted Answer

Introduction: Color in Portland cements arises largely from iron-containing phases. White cement requires special raw materials and process controls to achieve a bright, white appearance for architectural applications. Given Data / Assumptions: Iron oxide is the main coloring impurity in ordinary Portland cement. White cement targets minimal Fe2O3 and other coloring oxides. Other cement types (slag, pozzolan) do not specifically avoid iron. Concept / Approach: White cement uses low-iron limestone and kaolin (or other low-Fe clays) and sometimes fuel choices that avoid contamination. Kiln and finish grinding conditions further prevent color contamination. Pozzolan/slag/waterproof cements are defined by mineral additions or additives, not by eliminating iron oxide from the raw feed. Step-by-Step Solution: Identify the role of iron oxide in color: higher Fe → darker gray.Select cement type that minimizes iron: white cement.Conclude: white cement raw mix avoids iron-bearing minerals. Verification / Alternative check: Product specifications for white cement list very low Fe2O3 content, often below 0.5% by mass in clinker. Why Other Options Are Wrong: Pozzolan cement: uses reactive siliceous materials; color control is not the primary goal. Slag cement: ground granulated blast-furnace slag; iron may be present. Waterproof cement: property-modified OPC, not defined by iron exclusion. Common Pitfalls: Assuming finish paint or coatings determine cement color; intrinsic clinker chemistry is the dominant factor for white cement. Final Answer: White cement

Question 5

Lubrication engineering: mineral oils are preferred over fatty oils as lubricants primarily because fatty oils exhibit which disadvantages?

Accepted Answer

Introduction: Choosing between mineral and fatty (vegetable/animal) oils depends on stability, cost, and performance under operating conditions. This question asks why mineral oils are generally preferred in industrial lubrication. Given Data / Assumptions: Mineral oils are petroleum-derived hydrocarbons. Fatty oils are triglyceride-based and contain ester linkages. Industrial conditions may involve heat, oxygen, and moisture. Concept / Approach: Fatty oils contain ester bonds susceptible to hydrolysis in moist environments, producing acids that corrode metals. They also oxidize more readily, forming gums/varnish that impair machinery. At higher temperatures, triglycerides decompose more easily than refined mineral basestocks, increasing deposits and viscosity instability. Step-by-Step Solution: Assess thermal stability: fatty oils decompose sooner at high T.Assess oxidative stability: fatty oils oxidize faster → sludge/gum.Assess hydrolytic stability: ester linkages cleave in water → acids/soaps.Conclude that all listed disadvantages apply to fatty oils, hence mineral oils are preferred. Verification / Alternative check: Lubricant datasheets and ASTM tests (oxidation stability, hydrolytic stability) consistently show mineral oils and synthetic hydrocarbons outperforming many triglyceride oils under severe industrial conditions, though some specialty esters are engineered for stability. Why Other Options Are Wrong: Any single disadvantage alone understates the broader set of issues; all three are relevant. Common Pitfalls: Confusing modern synthetic esters (engineered for stability) with natural fatty oils; the question pertains to traditional fatty oils (e.g., vegetable/animal fats). Final Answer: All of the above

Question 6

Industrial bioproducts: gelatin (a nitrogenous protein used in foods, pharmaceuticals, and photography) is obtained by controlled hydrolysis of which natural material?

Accepted Answer

Introduction: Gelatin is widely used as a gelling agent and capsule material. Knowing its biological origin is important for food technology, pharmaceuticals, and ethical sourcing considerations. Given Data / Assumptions: Gelatin is a protein derived from animal connective tissues. Typical sources: skin, bones, and connective tissue of bovine/porcine/fish. Process: partial hydrolysis under controlled pH/temperature. Concept / Approach: Collagen is the structural protein forming triple helical fibrils in connective tissues. Hydrolysis (acid or alkaline) breaks specific bonds, converting insoluble collagen into soluble gelatin with characteristic bloom strength and gelling behavior. Tannins are polyphenols (used in leather tanning), molasses is a sugar-rich by-product, and starch is a carbohydrate—not proteins. Step-by-Step Solution: Identify the parent biomolecule: collagen (protein).Apply hydrolysis: controlled conditions unfold collagen triple helices.Obtain gelatin: protein product with gel-forming properties. Verification / Alternative check: Analytical profiles (amino acid composition rich in glycine, proline, hydroxyproline) confirm the collagen origin of gelatin. Why Other Options Are Wrong: Tannin: not a protein; a polyphenolic tanning agent. Molasses: carbohydrate mixture; no protein basis for gelatin. Starch: polysaccharide; yields dextrins/glucose on hydrolysis, not gelatin. Common Pitfalls: Equating gelatin with vegetarian hydrocolloids (agar, carrageenan, pectin); those have different polysaccharide origins and properties. Final Answer: Collagen

Question 7

Polymer materials — commercial name of polycaprolactam In industrial polymer science, polycaprolactam is commonly marketed under which fibre name used in textiles and engineering plastics?

Accepted Answer

Introduction / Context: This question checks your understanding of polymer nomenclature and trade names, especially as used in the textile and engineering plastics industries. Many polymers have systematic chemical names as well as commercial names that appear on product labels. Given Data / Assumptions: Polycaprolactam is the polymer formed by ring-opening polymerization of caprolactam. The options list common commercial fibres and plastics: nylon-6, nylon-66, dacron, and rayon. We assume standard industrial naming conventions. Concept / Approach: Nylons are polyamides. Nylon-6 comes from caprolactam, while nylon-66 is from hexamethylenediamine and adipic acid. Dacron is a trade name for polyethylene terephthalate (a polyester). Rayon is regenerated cellulose. Therefore, linking the correct commercial name requires recognizing the monomer and polymer family relationships. Step-by-Step Solution: Identify polycaprolactam → produced from caprolactam via ring-opening polymerization.Recall commercial naming: polycaprolactam is sold as nylon-6.Eliminate distractors: nylon-66 (different monomers), dacron (PET polyester), rayon (regenerated cellulose). Verification / Alternative check: Standard materials references and polymer textbooks uniformly equate polycaprolactam with nylon-6, used in fibres, films, and engineering parts (gears, bearings). Why Other Options Are Wrong: nylon-66: a different polyamide made from adipic acid and hexamethylenediamine. dacron: PET polyester, not a polyamide. rayon: regenerated cellulose, not a synthetic polyamide. Common Pitfalls: Confusing nylon-6 with nylon-66 because both are polyamides; the “6” vs “66” indicates monomer origin. Final Answer: nylon-6

Question 8

Gas liquefaction methods — the Claude process In cryogenic engineering, the Claude process for gas liquefaction is distinguished by the inclusion of which key step in addition to heat exchange?

Accepted Answer

Introduction / Context: Liquefaction processes use combinations of compression, heat exchange, and expansion to lower a gas temperature below its saturation temperature. The Claude process is a foundational cycle in cryogenics. Given Data / Assumptions: The question contrasts different cooling/expansion steps. We assume idealized descriptions of Linde vs Claude cycles. Concept / Approach: The Linde cycle relies primarily on isenthalpic (Joule–Thomson) throttling after regenerative precooling. The Claude cycle adds a work-producing, near-isentropic (adiabatic) expansion in an expander (piston or turbine). This additional adiabatic expansion yields larger temperature drops, improving liquefaction efficiency. Step-by-Step Solution: Identify the hallmark of Claude: expansion turbine/piston allowing external work.Recognize that mere compression above critical pressure is insufficient for liquefaction.Joule–Thomson only describes Linde-style throttling, not uniquely Claude.Thus, the correct distinguishing step is adiabatic expansion in an expander. Verification / Alternative check: Process schematics show the Claude expander branch delivering work and deeper cooling before JT valve, enhancing liquid yield. Why Other Options Are Wrong: Merely compressing above critical pressure does not ensure liquefaction upon cooling. Joule–Thomson only: not unique to Claude; also less efficient at high temperatures. Heat exchange only: necessary but not the defining feature. Common Pitfalls: Equating all liquefaction cycles; ignoring the role of isentropic expansion work. Final Answer: Adiabatic expansion against a piston or in an expansion turbine

Question 9

Food technology — definition of pasteurization In dairy processing, what does pasteurization of milk specifically mean regarding microbial control and product quality?

Accepted Answer

Introduction / Context: Pasteurization is a cornerstone of food safety. For milk, it targets pathogenic microorganisms while preserving the sensory and nutritional qualities as much as possible. Given Data / Assumptions: Pasteurization involves heat treatment under controlled time–temperature conditions (e.g., HTST 72°C for 15 s or LTLT 63°C for 30 min). Goal: destroy pathogens and reduce spoilage organisms without sterilizing the product. Concept / Approach: Heat denatures critical cellular proteins and inactivates enzymes in pathogens. Proper control avoids significant changes in flavor, color, and nutritional composition. It is more than mere growth inhibition; it achieves lethal effects on target organisms. Step-by-Step Solution: Define pasteurization → controlled heat treatment to kill pathogens.Restrict scope → not removal of fat/proteins; not just bacteriostasis.Select the option that matches: option (b). Verification / Alternative check: Food codes and dairy standards define pasteurization exactly in terms of time–temperature lethality for specified pathogens. Why Other Options Are Wrong: Option (a): describes separation/clarification, not microbial kill. Option (c): underplays lethality; pasteurization kills targeted microbes. Option (d): incorrect because a correct definition is present. Common Pitfalls: Confusing pasteurization with sterilization (UHT) or mere refrigeration (bacteriostasis). Final Answer: Killing organisms by heating at a controlled temperature without changing the milk’s natural characteristics

Question 10

Organic chemistry — understanding esterification Which statement correctly characterizes an esterification reaction in organic chemistry?

Accepted Answer

Introduction / Context: Esterification is a fundamental transformation in organic chemistry used to form esters, which appear in flavors, fragrances, solvents, and polymers. Understanding what esterification is (and is not) avoids confusion with related reactions like saponification. Given Data / Assumptions: Classical Fischer esterification involves an alcohol and a carboxylic acid with an acid catalyst. Water is formed as a by-product, and the reaction is reversible. Concept / Approach: In Fischer esterification, the key equilibrium is: alcohol + carboxylic acid ⇌ ester + water (acid-catalyzed). Driving the equilibrium (e.g., removing water) increases ester yield. Soapmaking (saponification) is a different reaction: base-catalyzed hydrolysis of esters (fats) to yield glycerol and soaps. Step-by-Step Solution: Identify reactants: alcohol + carboxylic acid.Identify products: ester + water.Note reversibility: equilibrium reaction sensitive to water removal or excess reactant.Select the option that captures these features → option (b). Verification / Alternative check: Standard texts describe Fischer esterification as reversible; Le Châtelier’s principle applies via water removal or reactant excess. Why Other Options Are Wrong: Option (a): describes saponification/soap formation, not esterification. Option (c): incorrect on both irreversibility and reactants. Option (d): polymerization of ethene forms polyethylene, not polyesters; polyesters come from diols + diacids/derivatives or ring-opening of lactones. Common Pitfalls: Confusing esterification with soapmaking (reverse direction under basic conditions). Final Answer: It is reversible and occurs between an alcohol and a carboxylic acid

Chemical Process Questions