Formaldehyde
Formaldehyde is a colorless gas synthesized by the oxidation of methanol and used as an antiseptic, disinfectant, histologic fixative, and general-purpose chemical reagent for lab applications. Formaldehyde is readily soluble in water and is typically dispersed as a 37% solution in water; formalin, a 10% solution of formaldehyde in water, is utilized as a disinfectant and to maintain biological specimens.
Environmentally, formaldehyde might be found in the environment, smoke from fires, vehicle exhaust, and cigarette smoke. Small amounts are produced during common metabolic processes in many organisms, including human beings.
Structure of Formaldehyde
Formaldehyde includes one carbon atom that shares a double bond with an oxygen atom. The carbon’s remaining electron-sharing slots are occupied by two hydrogen atoms. The polar nature of its carbon-oxygen bond makes this a highly reactive substance.
The oxygen atom draws in electrons more strongly than the carbon atom, resulting in a partial negative charge at one end of the compound and a partial positive charge at the other. This triggers it to “stick” to other polar particles and provides it some capability to accept and donate electrons.
Properties of Formaldehyde
Formaldehyde reacts with a base like sodium hydroxide and forms salt formate and methanol. The chemical equation is listed below.
2HCHO + NaOH → HCOONa + CH3OH
Formaldehyde reacts with ammonia forms formamidine and water. The chemical equation is listed below.
6HCHO + 4NH3 → (CH2)6N4 + 6H2O
Preparation of Formaldehyde
(i) Lab Method
Formaldehyde is prepared in the laboratory by passing a mixture of methyl alcohol vapours and air over platinized asbestos or copper or silver catalyst at 300C.
Set up the apparatus.
Air is drawn through methyl alcohol with the help of a suction pump. Methyl alcohol is oxidized to gaseous formaldehyde which is absorbed in water. The resulting mix is called formalin. Formalin is a mix of 40 % formaldehyde, 8% methyl alcohol, and 52 % water.
(ii) Industrial method
Formaldehyde is manufactured by passing a mix of methanol vapours and air over iron oxide-molybdenum oxide or silver driver at 500 ° C.
Uses of Formaldehyde
- (i) It is utilized in the manufacture of resins like urea-formaldehyde and plastics such as Bakelite.
- (ii) It is used in the manufacture of dyes such as indigo, para-rosaniline, and so on.
- (iii) It’s 40% aqueous solution called formalin is used as an antiseptic, a disinfectant, a germicide, a fungicide, and for maintaining animal specimens and sterilizing surgical instruments.
- (iv) It is used as a decolorizing agent in barrel dyeing.
- (v) It is used in the silvering of mirrors.
- (vi) It is utilized in making medicine urotropine used as a urinary antibacterial.
- (vii) It is utilized in making formamint (formaldehyde + lactose) utilized as throat lozenges.
- (viii) It is utilized in the processing of the anti-polio vaccine.
MCQs with Answers: Formaldehyde
- 1. What is the primary source of formaldehyde production?
- a) Direct synthesis
- b) Oxidation of methane
- c) Oxidation of methanol
- d) Industrial combustion
Answer: c) Oxidation of methanol
- 2. How is formaldehyde typically dispersed for applications?
- a) Gaseous form
- b) 10% solution in water (formalin)
- c) Solid crystals
- d) Vaporized form
Answer: b) 10% solution in water (formalin)
- 3. What is the primary use of formaldehyde in the manufacture of resins?
- a) Polyester resins
- b) Urea-formaldehyde resins
- c) Epoxy resins
- d) Silicone resins
Answer: b) Urea-formaldehyde resins
- 4. Which of the following is NOT a property of formaldehyde?
- a) Highly reactive
- b) Colorless gas
- c) Insoluble in water
- d) Polar nature in carbon-oxygen bond
Answer: c) Insoluble in water
- 5. What environmental sources might contribute to formaldehyde presence?
- a) Ocean water
- b) Volcanic eruptions
- c) Vehicle exhaust
- d) All of the above
Answer: c) Vehicle exhaust
- 6. How does formaldehyde react with a base like sodium hydroxide?
- a) Forms salt formate and methanol
- b) Forms water and oxygen
- c) Forms carbon dioxide
- d) Undergoes no reaction
Answer: a) Forms salt formate and methanol
- 7. Which catalyst is used in the lab method of formaldehyde preparation?
- a) Iron oxide-molybdenum oxide
- b) Platinum
- c) Silver
- d) Copper
Answer: b) Platinum
- 8. What is the temperature range for the industrial method of formaldehyde preparation?
- a) 100 °C – 200 °C
- b) 300 °C – 400 °C
- c) 500 °C
- d) 700 °C – 800 °C
Answer: c) 500 °C
- 9. What is the chemical formula of formamint?
- a) CH3OH
- b) (CH2)6N4
- c) HCOONa
- d) CH3CHO
Answer: b) (CH2)6N4
- 10. What is the primary purpose of formaldehyde in the silvering of mirrors?
- a) To enhance reflectivity
- b) To prevent corrosion
- c) To dissolve impurities
- d) To improve color
Answer: a) To enhance reflectivity
- 11. In which industrial process is formaldehyde used as a decolorizing agent?
- a) Paper manufacturing
- b) Metal extraction
- c) Barrel dyeing
- d) Petroleum refining
Answer: c) Barrel dyeing
- 12. What is the primary use of formaldehyde in the processing of the anti-polio vaccine?
- a) Sterilization
- b) Preservation
- c) Immunization
- d) Decolorization
Answer: c) Immunization
- 13. What is the chemical composition of formalin?
- a) 10% formaldehyde, 90% water
- b) 40% formaldehyde, 8% methanol, 52% water
- c) 20% formaldehyde, 80% ethanol
- d) 30% formaldehyde, 70% acetone
Answer: b) 40% formaldehyde, 8% methanol, 52% water
- 14. Which chemical reaction does formaldehyde undergo with ammonia?
- a) Combustion
- b) Substitution
- c) Esterification
- d) Formation of formamidine
Answer: d) Formation of formamidine
- 15. What is the primary reason formaldehyde is used in the silvering of mirrors?
- a) To prevent tarnishing
- b) To enhance adhesion
- c) To provide color
- d) To inhibit bacterial growth
Answer: b) To enhance adhesion
- 16. What is the common name for a 10% solution of formaldehyde in water?
- a) Methanol
- b) Ethanol
- c) Formalin
- d) Formic acid
Answer: c) Formalin
- 17. In the lab method, what is the function of platinized asbestos or copper?
- a) Catalyst for oxidation
- b) Absorbent for water
- c) Filter for impurities
- d) Stabilizer for temperature
Answer: a) Catalyst for oxidation
- 18. How does the polar nature of the carbon-oxygen bond impact formaldehyde’s reactivity?
- a) Reduces reactivity
- b) Increases reactivity
- c) No impact on reactivity
- d) Changes color
Answer: b) Increases reactivity
- 19. What role does formaldehyde play in the manufacture of dyes such as indigo?
- a) Solvent
- b) Reducing agent
- c) Catalyst
- d) Precipitating agent
Answer: a) Solvent
- 20. Which of the following is NOT a common use of formaldehyde?
- a) Synthesizing polymers
- b) Sterilizing surgical instruments
- c) Fertilizer production
- d) Making throat lozenges
Answer: c) Fertilizer production
- 21. What is the primary advantage of using formaldehyde in the preservation of biological specimens?
- a) Enhances color
- b) Inhibits microbial growth
- c) Reduces viscosity
- d) Increases flexibility
Answer: b) Inhibits microbial growth
Wrapping up: Formaldehyde – Structure, Properties, Preparation, and Uses
Formaldehyde, a colorless gas, is synthesized through methanol oxidation and finds diverse applications as an antiseptic, disinfectant, histologic fixative, and chemical reagent in laboratories. It dissolves readily in water, commonly distributed as a 37% solution (formalin) or a 10% solution for disinfection and biological specimen preservation.
Structure: Formaldehyde comprises one carbon atom with a double bond to an oxygen atom, and the remaining electron-sharing slots occupied by two hydrogen atoms. Its polar carbon-oxygen bond enhances reactivity, leading to partial negative and positive charges at opposite ends, enabling interactions with polar particles.
Properties: Formaldehyde reacts with sodium hydroxide, forming salt formate and methanol. It also reacts with ammonia, yielding formamidine and water. These reactions demonstrate its chemical versatility and reactivity.
Preparation: Lab Method: Produced in the laboratory by passing methyl alcohol vapors and air over platinized asbestos or copper catalyst at 300°C. Industrial Method: Manufactured industrially by passing a mix of methanol vapors and air over iron oxide-molybdenum oxide or silver catalyst at 500°C.
Uses:
- Resin and Plastics: Utilized in manufacturing resins like urea-formaldehyde and plastics such as Bakelite.
- Dyes Production: Involved in the production of dyes like indigo and para-rosaniline.
- Disinfectant and Preservative: Its 40% aqueous solution, formalin, acts as an antiseptic, disinfectant, germicide, and fungicide. It is crucial for maintaining animal specimens and sterilizing surgical instruments.
- Barrel Dyeing: Acts as a decolorizing agent in barrel dyeing processes.
- Mirrors Silvering: Used in the silvering process of mirrors.
- Medicine Production: Plays a role in producing urotropine, a medicine used as a urinary antibacterial.
- Throat Lozenges: Utilized in making formamint (formaldehyde + lactose) for throat lozenges.
- Vaccine Processing: Involved in the processing of the anti-polio vaccine.
Formaldehyde’s diverse applications showcase its significance across various industries, contributing to materials, healthcare, and research endeavors.