General methods of preparation of inorganic compounds MCQs With Answer

General Methods of Preparation of Inorganic Compounds MCQs With Answer for B. Pharm

Mastering the general methods of preparation of inorganic compounds is essential for B. Pharm students studying pharmaceutical inorganic chemistry. This topic covers key techniques such as precipitation, neutralization, redox reactions, double decomposition, thermal decomposition, hydrolysis, complex formation, solvent extraction, and crystallization—critical for preparing pharmaceutical-grade salts, oxides, hydroxides, and acids. Learn how pH, temperature, reagent purity, common-ion effect, and washing/drying conditions affect yield, particle size, and purity. These MCQs emphasize lab-scale preparation, pharmacopeial quality (assay, LOD), safety, and scalability in pharmacy practice. Perfect for exams and quick revision, this quiz strengthens both concepts and applications. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which general method is most suitable for preparing insoluble salts like BaSO4 from soluble precursors?

• Precipitation (double decomposition)
• Direct combination
• Thermal decomposition
• Electrolysis

Correct Answer: Precipitation (double decomposition)

Q2. In neutralization reactions used to prepare inorganic salts, the typical byproduct formed is:

• Water
• Hydrogen gas
• Chlorine gas
• Carbon monoxide

Correct Answer: Water

Q3. The common-ion effect is primarily used during precipitation to:

• Decrease solubility and enhance precipitation
• Increase solubility and prevent precipitation
• Increase oxidation potential
• Decrease boiling point of the solvent

Correct Answer: Decrease solubility and enhance precipitation

Q4. Which method is typically used to prepare CaO from CaCO3?

• Thermal decomposition (calcination)
• Neutralization
• Hydrolysis
• Precipitation

Correct Answer: Thermal decomposition (calcination)

Q5. The Solvay process mainly prepares:

• Sodium carbonate
• Sodium chloride
• Sodium hydroxide
• Sodium sulfate

Correct Answer: Sodium carbonate

Q6. During precipitation of metal hydroxides, controlling pH is critical because:

• Solubility of hydroxides is strongly pH-dependent
• pH alters molar mass of the product
• pH changes the flame test color
• pH prevents filtration

Correct Answer: Solubility of hydroxides is strongly pH-dependent

Q7. Preparation of AgCl from AgNO3 and NaCl is an example of:

• Double displacement precipitation
• Direct synthesis
• Redox reaction
• Thermal decomposition

Correct Answer: Double displacement precipitation

Q8. For obtaining pure crystals after precipitation, the step of “digestion” helps to:

• Grow larger, purer crystals by Ostwald ripening
• Increase nucleation rate only
• Introduce impurities intentionally
• Lower the melting point

Correct Answer: Grow larger, purer crystals by Ostwald ripening

Q9. Which reagent pair is best to prepare Mg(OH)2 as a pharmaceutical antacid by precipitation?

• MgCl2 and NaOH
• MgSO4 and H2SO4
• MgO and CO2
• Mg and HCl

Correct Answer: MgCl2 and NaOH

Q10. Drying a hydrate like CuSO4·5H2O at too high temperature may lead to:

• Loss of water of crystallization
• Formation of peroxides
• Incorporation of solvent
• Increase in pH

Correct Answer: Loss of water of crystallization

Q11. To minimize peptization of precipitates like ferric hydroxide during washing, one should use:

• Electrolyte-containing wash solutions
• Pure deionized water only
• Hot organic solvents
• Strong oxidizing agents

Correct Answer: Electrolyte-containing wash solutions

Q12. Which technique is preferred to prepare high-purity H2 via inorganic methods?

• Reaction of Zn with dilute H2SO4 and purification
• Electrolysis of molten NaCl
• Thermal decomposition of NaHCO3
• Chlorination of methane

Correct Answer: Reaction of Zn with dilute H2SO4 and purification

Q13. Preparation of bleaching powder involves:

• Chlorination of slaked lime
• Oxidation of NaCl with KMnO4
• Direct combination of Ca and Cl2
• Thermal decomposition of CaSO4

Correct Answer: Chlorination of slaked lime

Q14. Which method is used to prepare anhydrous AlCl3 in industry?

• Direct combination of Al and Cl2 at high temperature
• Neutralization of Al(OH)3 with HCl in water
• Electrolysis of Al2O3 in cryolite
• Precipitation using NaCl

Correct Answer: Direct combination of Al and Cl2 at high temperature

Q15. A key reason for using excess precipitating reagent is to:

• Drive the equilibrium toward product formation
• Increase ionic strength to dissolve the product
• Decrease yield intentionally
• Reduce the melting point of the product

Correct Answer: Drive the equilibrium toward product formation

Q16. Which pair best illustrates a redox-based preparation of an inorganic compound?

• Preparation of KMnO4 from MnO2 by oxidation
• Formation of NaCl from NaOH and HCl
• Precipitation of BaSO4 from BaCl2 and Na2SO4
• Hydrolysis of SiCl4 to H4SiO4

Correct Answer: Preparation of KMnO4 from MnO2 by oxidation

Q17. During crystallization, a “mother liquor” refers to:

• Residual solution remaining after crystals have formed
• First wash solvent used
• Dilute acid prewash
• Slurry of crystals before filtration

Correct Answer: Residual solution remaining after crystals have formed

Q18. In the Solvay process, NH3 is used primarily to:

• Increase CO2 absorption and precipitate NaHCO3
• Oxidize NaCl to Na2CO3
• Reduce CaCO3 to CaO
• Hydrolyze Cl− ions

Correct Answer: Increase CO2 absorption and precipitate NaHCO3

Q19. A pharmaceutical-grade precipitate should be washed to remove:

• Adhering mother liquor and soluble impurities
• Water of crystallization
• Crystal habit modifiers
• Bound oxygen

Correct Answer: Adhering mother liquor and soluble impurities

Q20. Which of the following best minimizes co-precipitation of impurities?

• Slow addition of reagents with stirring and digestion
• Rapid dumping of reagents without stirring
• Using highly supersaturated solutions
• Avoiding any washing step

Correct Answer: Slow addition of reagents with stirring and digestion

Q21. Sodium thiosulfate (Na2S2O3) can be prepared by boiling Na2SO3 with:

• Sulfur
• Chlorine
• Hydrogen peroxide
• Calcium carbonate

Correct Answer: Sulfur

Q22. The preparation of NaOH industrially from brine uses:

• Chlor-alkali process (electrolysis of brine)
• Solvay process
• Thermal cracking
• Precipitation with Na2CO3

Correct Answer: Chlor-alkali process (electrolysis of brine)

Q23. Hydrolysis as a method of preparation is exemplified by converting SiCl4 to:

• Silicic acid (H4SiO4) and HCl
• Silicon carbide and H2
• Silicon nitride and HCl
• Silicon metal and Cl2

Correct Answer: Silicic acid (H4SiO4) and HCl

Q24. Thermal decomposition of ammonium dichromate yields:

• Cr2O3, N2, and H2O
• CrO, NH3, and O2
• CrO3 only
• CrCl3 and HCl

Correct Answer: Cr2O3, N2, and H2O

Q25. To precipitate CaCO3 for antacid use, an effective route is:

• Reacting CaCl2 with Na2CO3
• Burning Ca with CO2 directly
• Electrolysis of CaCO3
• Oxidation of CaO with H2O

Correct Answer: Reacting CaCl2 with Na2CO3

Q26. In preparing FeSO4 from scrap iron, the process uses:

• Redox reaction with dilute H2SO4
• Precipitation with Na2SO4
• Thermal decomposition of Fe2(SO4)3
• Direct combination of Fe and SO3 gas

Correct Answer: Redox reaction with dilute H2SO4

Q27. Which parameter most strongly influences the particle size of a precipitated salt?

• Degree of supersaturation
• Molar conductivity
• Color of the solution
• Flame test intensity

Correct Answer: Degree of supersaturation

Q28. A key purification step after precipitation to improve pharmaceutical quality is:

• Recrystallization
• Sublimation
• Distillation under vacuum
• Electroplating

Correct Answer: Recrystallization

Q29. When preparing sodium bicarbonate in the Solvay process, the immediate solid formed is:

• NaHCO3
• Na2CO3·10H2O
• NaOH
• Natrium

Correct Answer: NaHCO3

Q30. Which combination best prepares NH4Cl by a general method?

• Neutralization of NH3 with HCl
• Oxidation of NH3 with KMnO4
• Precipitation from NH4NO3 and NaCl
• Thermal decomposition of (NH4)2CO3

Correct Answer: Neutralization of NH3 with HCl

Q31. To prepare high-purity BaSO4 for radiographic uses, which precaution is most important?

• Use sulfate free from soluble Ba2+ impurities
• Use acidic wash to dissolve BaSO4
• Dry at red heat to remove all sulfate
• Add complexing agents to dissolve Ba2+

Correct Answer: Use sulfate free from soluble Ba2+ impurities

Q32. For preparing H2O2 in laboratory, an applicable method is:

• Acidifying Na2O2 with dilute acid and careful stabilization
• Heating H2O vigorously
• Electrolyzing NaCl solution
• Reacting O2 with H2 directly at room temperature

Correct Answer: Acidifying Na2O2 with dilute acid and careful stabilization

Q33. The role of a complexing agent (e.g., NH3) during selective precipitation is to:

• Keep certain metal ions in solution as complexes
• Oxidize metal ions selectively
• Reduce the ionic product of water
• Increase the melting point of the precipitate

Correct Answer: Keep certain metal ions in solution as complexes

Q34. Roasting of metal sulfides (e.g., ZnS) primarily converts them to:

• Metal oxides and SO2
• Metal chlorides and O2
• Metal hydroxides and H2S
• Metal sulfates and H2

Correct Answer: Metal oxides and SO2

Q35. In precipitation of Al(OH)3, a gelatinous precipitate forms. To improve filterability, one should:

• Digest the precipitate at elevated temperature
• Use ice-cold solutions only
• Add strong oxidizers
• Increase stirring speed only

Correct Answer: Digest the precipitate at elevated temperature

Q36. The selective precipitation of CaC2O4 over MgC2O4 is favored by:

• Adjusting pH and controlling oxalate concentration
• Adding strong acid in excess to dissolve both
• Using very high temperature
• Adding chloride ions as a masking agent

Correct Answer: Adjusting pH and controlling oxalate concentration

Q37. Which general method is used to prepare PCl3 from P and Cl2?

• Direct combination
• Precipitation
• Neutralization
• Hydrolysis

Correct Answer: Direct combination

Q38. Calcination differs from roasting in that calcination is typically carried out:

• In absence or limited supply of air
• In chlorine atmosphere
• Under high pressure of hydrogen
• Only in aqueous phase

Correct Answer: In absence or limited supply of air

Q39. In preparing pharmaceutical MgO, the precursor commonly decomposed is:

• MgCO3
• MgCl2
• MgSO4·7H2O
• Mg(OH)2Cl

Correct Answer: MgCO3

Q40. During crystallization, seeding is performed to:

• Initiate controlled crystal growth
• Increase solubility sharply
• Hydrolyze impurities
• Elevate boiling point

Correct Answer: Initiate controlled crystal growth

Q41. The preparation of KAl(SO4)2·12H2O (alum) typically involves:

• Crystallization from equimolar K2SO4 and Al2(SO4)3 solutions
• Direct combination of K, Al, and S
• Electrolysis of alumina
• Oxidation of Al(OH)3 with KMnO4

Correct Answer: Crystallization from equimolar K2SO4 and Al2(SO4)3 solutions

Q42. Which statement about “loss on drying (LOD)” is correct for inorganic preparations?

• It estimates moisture and volatile content affecting purity
• It measures only crystal size
• It determines oxidation state
• It quantifies chloride content

Correct Answer: It estimates moisture and volatile content affecting purity

Q43. In preparing sodium phosphate buffers, the general method used is:

• Neutralization and controlled mixing of acid/base salts
• Thermal decomposition of NaH2PO4
• Chlorination of H3PO4
• Electrolysis of phosphate solutions

Correct Answer: Neutralization and controlled mixing of acid/base salts

Q44. A reason to use ethanol-water mixtures during washing/crystallization is to:

• Reduce solubility losses of the product
• Increase ignition residue
• Promote deliquescence
• Increase co-precipitation

Correct Answer: Reduce solubility losses of the product

Q45. Which reaction best illustrates displacement (metathesis) in inorganic preparation?

• CuSO4 + Zn → ZnSO4 + Cu
• NaOH + HCl → NaCl + H2O
• CaCO3 → CaO + CO2
• SiCl4 + 2H2O → H4SiO4 + 4HCl

Correct Answer: CuSO4 + Zn → ZnSO4 + Cu

Q46. For preparing pure NaCl from brine, an essential purification step is:

• Precipitating Ca2+ and Mg2+ as carbonates/hydroxides
• Adding excess HCl to dissolve NaCl
• Roasting with sulfur
• Electroplating sodium

Correct Answer: Precipitating Ca2+ and Mg2+ as carbonates/hydroxides

Q47. The best method to prepare Ca(OH)2 (slaked lime) from CaO is:

• Hydration (slaking) with controlled addition of water
• Electrolysis of CaO
• Chlorination of CaCO3
• Neutralization of CaO with HCl

Correct Answer: Hydration (slaking) with controlled addition of water

Q48. Controlled atmosphere (e.g., inert gas) is required during preparation of:

• Moisture- or air-sensitive halides like FeCl2
• BaSO4 from BaCl2 and Na2SO4
• NaCl from HCl and NaOH
• CaCO3 by precipitation

Correct Answer: Moisture- or air-sensitive halides like FeCl2

Q49. The purpose of aging a gel in sol–gel preparation of oxides is to:

• Promote polycondensation and strengthen the network
• Increase impurity incorporation
• Hydrolyze the final oxide back to salt
• Reduce pore formation completely

Correct Answer: Promote polycondensation and strengthen the network

Q50. In pharmaceutical inorganic preparations, choosing reagents of analytical or pharmacopeial grade is critical mainly to:

• Limit toxic impurities and meet quality standards
• Increase color intensity of products
• Lower melting points for easy drying
• Avoid the need for filtration

Correct Answer: Limit toxic impurities and meet quality standards