கொஞ்சம் கெமிஸ்ட்ரி ! - EP.008

 

Chemical Properties

• Formula: CH₂O

• Molar Mass: 30.03 g/mol

• Appearance: Colorless gas or aqueous solution

• Odor: Pungent, irritating odor

• Density: 1.09 g/cm³ (gas), 1.08 g/cm³ (aqueous solution, 37%)

• Melting Point: -92°C (-134°F)

• Boiling Point: -19°C (-2°F) (gas), varies with concentration for the aqueous solution

• Solubility: Highly soluble in water, forming formalin; also soluble in alcohols and other polar solvents

Physical Properties

• State: Gas at standard temperature and pressure (STP), but commonly used as an aqueous solution (formalin)

• Structure: Simple aldehyde with a carbonyl group (C=O) bonded to two hydrogen atoms

Preparation

• Laboratory Method: Produced by the catalytic oxidation of methanol (CH₃OH) using a silver or copper catalyst:

$${\text{<span style="font-family: Diphylleia;">CH</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">3</span>}}\text{<span style="font-family: Diphylleia;">OH</span>}<span\; style="font-family:\; Diphylleia;">+</span>\frac{\mathrm{<span\; style="font-family:\; Diphylleia;">1</span>}}{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}{\text{<span style="font-family: Diphylleia;">O</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}<span\; style="font-family:\; Diphylleia;">\to </span>{\text{<span style="font-family: Diphylleia;">CH</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}\text{<span style="font-family: Diphylleia;">O</span>}<span\; style="font-family:\; Diphylleia;">+</span>{\text{<span style="font-family: Diphylleia;">H</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}\text{<span style="font-family: Diphylleia;">O</span>}\backslash text\{CH\}\_3\backslash text\{OH\}\; +\; \backslash frac\{1\}\{2\}\; \backslash text\{O\}\_2\; \backslash rightarrow\; \backslash text\{CH\}\_2\backslash text\{O\}\; +\; \backslash text\{H\}\_2\backslash text\{O\}$$

• Industrial Method: Produced by the oxidation of methanol in the presence of a metal oxide catalyst, such as iron oxide or molybdenum oxide.

Uses

• Chemical Industry: Used in the production of various chemicals, such as urea-formaldehyde resins, phenol-formaldehyde resins, and polyacetal resins.

• Laboratory Reagent: Used in analytical chemistry and various laboratory processes.

• Medical: Used as a disinfectant, preservative, and in the preparation of vaccines.

• Textile Industry: Used in the treatment of fabrics to make them wrinkle-resistant.

• Construction: Used in the production of plywood, particleboard, and other building materials.

Safety and Hazards

• Hazard Statements: H301 (Toxic if swallowed), H311 (Toxic in contact with skin), H331 (Toxic if inhaled), H314 (Causes severe skin burns and eye damage), H317 (May cause an allergic skin reaction), H350 (May cause cancer)

• Precautionary Statements: P201 (Obtain special instructions before use), P280 (Wear protective gloves/protective clothing/eye protection/face protection), P301+P310 (IF SWALLOWED: Immediately call a POISON CENTER or doctor/physician), P305+P351+P338 (IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing), P308+P313 (IF exposed or concerned: Get medical advice/attention)

• NFPA 704 (Fire Diamond): 3 (Health), 2 (Flammability), 0 (Reactivity)

• Lethal Dose (LD50): 100 mg/kg (rat, oral)

Environmental Impact

• Air Pollution: Formaldehyde is a significant air pollutant and can contribute to the formation of ground-level ozone and smog.

• Water Pollution: Formaldehyde can contaminate water sources and pose a risk to aquatic life.

Handling and Storage

• Handling: Use in well-ventilated areas; avoid inhalation and contact with skin and eyes; use appropriate personal protective equipment (PPE).

• Storage: Store in tightly sealed containers made of corrosion-resistant materials; keep away from incompatible substances such as bases and oxidizers.

Health Effects

• Inhalation: Can cause sore throat, coughing, shortness of breath, and respiratory irritation.

• Skin Contact: May cause irritation, redness, and burns.

• Eye Contact: Causes severe eye irritation and damage.

• Ingestion: Can cause gastrointestinal irritation, nausea, vomiting, and potentially fatal poisoning.

Detection and Measurement

• Odorization: Formaldehyde has a distinct, pungent odor that can be detected at low concentrations.

• Sensors: Formaldehyde detectors and sensors are used in various industries to monitor and prevent leaks and ensure safety.

Chemical Reactions

• Combustion: Formaldehyde undergoes complete combustion in the presence of oxygen to produce carbon dioxide and water vapor:

$${\text{<span style="font-family: Diphylleia;">CH</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}\text{<span style="font-family: Diphylleia;">O</span>}<span\; style="font-family:\; Diphylleia;">+</span>{\text{<span style="font-family: Diphylleia;">O</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}<span\; style="font-family:\; Diphylleia;">\to </span>{\text{<span style="font-family: Diphylleia;">CO</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}<span\; style="font-family:\; Diphylleia;">+</span>{\text{<span style="font-family: Diphylleia;">H</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}\text{<span style="font-family: Diphylleia;">O</span>}\backslash text\{CH\}\_2\backslash text\{O\}\; +\; \backslash text\{O\}\_2\; \backslash rightarrow\; \backslash text\{CO\}\_2\; +\; \backslash text\{H\}\_2\backslash text\{O\}$$

• Polymerization: Formaldehyde can polymerize to form paraformaldehyde, a solid polymer used in various applications.

Industrial Applications

• Resin Production: Used in the production of urea-formaldehyde resins, phenol-formaldehyde resins, and melamine-formaldehyde resins.

• Disinfectants: Used as a disinfectant and preservative in medical and laboratory settings.

• Textile Treatment: Used to treat fabrics to make them wrinkle-resistant and durable.

• Construction Materials: Used in the production of plywood, particleboard, and other building materials.