Laboratory Preparation of Carbon Dioxide
Discover the fascinating world of CO₂ through interactive simulation and experiments.
Theoretical Foundation
History of CO₂
Discovery: Carbon dioxide was identified in the 17th century by Flemish chemist Jan Baptist van Helmont, who noticed a gas produced during fermentation and combustion.
1751: Joseph Black conducted systematic studies on “fixed air” (CO₂), discovering its unique properties and role in chemical reactions.
1822: Thomas Andrews conducted experiments on CO₂ at high pressures and temperatures, discovering its liquefaction point.
Modern era: Today, CO₂ is recognized as crucial for photosynthesis, climate science, and numerous industrial applications.
General Information
| Chemical name | Carbon dioxide |
| Formula | CO₂ |
| Molecular weight | 44.01 g/mol |
| CAS number | 124-38-9 |
| Colour | Colourless |
| Odour | Odourless (slightly pungent at high conc.) |
| Density | 1.98 kg/m³ (gas at STP) |
| Solubility | 1.45 g/L in water at 25°C |
| State | Gas (at room temperature) |
| Boiling point | -78.5°C (sublimes) |
| Critical temp. | 31.1°C |
| Critical pressure | 73.8 bar |
Molecular Structure
Natural Occurrence
- Atmosphere: ~0.04% by volume (410+ ppm)
- Respiration: Released by all living organisms during cellular respiration
- Fermentation: Produced during decomposition and microbial processes
- Volcanic activity: Released from Earth’s interior through volcanic emissions
- Oceanic sources: Released from warming waters and carbonate dissolution
- Photosynthesis: Part of the natural carbon cycle
Total atmospheric CO₂ is approximately 1,800 Gt (gigatons), constantly cycling between atmosphere, biosphere, and hydrosphere.
Physical Properties
- Colour: Colourless gas
- Odour: Odourless (or faintly pungent at high concentrations)
- Density: Denser than air (1.98 kg/m³ vs. 1.29 kg/m³ for air)
- Solubility: Slightly soluble in water, forms carbonic acid
- Sublimation: Transitions directly from solid to gas at -78.5°C
- Compressibility: Highly compressible; liquefiable under pressure
- Dry ice: Solid CO₂ at -78.5°C, used as refrigerant
Chemical Properties
CO₂ + H₂O → H₂CO₃Carbonic acid forms; slightly acidic solution
CO₂ + Ca(OH)₂ → CaCO₃↓ + H₂OWhite precipitate; diagnostic test for CO₂
CO₂ is an acidic oxide; supports photosynthesis in plants
CO₂ extinguishes burning materials; used in fire extinguishers
Laboratory Experiment Setup
Experiment Controls
Why Each Apparatus is Used
Conical Flask
Function: Contains reactants (marble chips and dilute HCl)
Material: Borosilicate glass (heat-resistant)
Why: Holds liquids and solids safely during reaction
Alternative: Round-bottom flask or test tube
Thistle Funnel
Function: Allows controlled addition of acid
Material: Borosilicate glass with rubber tubing
Why: Enables regulation of reaction rate
Alternative: Separatory funnel or dropper
Delivery Tube
Function: Transports evolved gas to collection jar
Material: Glass tube with rubber connectors
Why: Directs gas safely from flask to jar
Alternative: Graduated glass tube
Gas Jar
Function: Collects and stores evolved CO₂
Material: Borosilicate glass with ground glass joint
Why: Allows observation and collection of gas
Alternative: Round-bottom flask or gas washing bottle
Collection Methods of CO₂
Downward Displacement of Air
Principle: CO₂ (M = 44 g/mol) is denser than air (M ≈ 29 g/mol). CO₂ sinks and fills the jar from the bottom; air is displaced upward and escapes.
Advantage: Simple, effective, no consumables needed
Upward Displacement of Air
Principle: Delivery tube reaches near the bottom of the jar. Gas enters from the bottom, displacing air upward through the tube opening at the top.
Advantage: Better for lighter gases; precise collection control
Why NOT Water Displacement?
Problem: CO₂ is slightly soluble in water (1.45 g/L at 25°C). It dissolves instead of collecting as pure gas.
Result: Impure sample, incomplete collection, wrong volume measurements
Identification Tests for CO₂
Lime Water Test (Ca(OH)₂)
Primary TestChemical equation
CO₂ + Ca(OH)₂ → CaCO₃↓ + H₂O
Observations
- Initial: Clear colourless solution
- During CO₂ passage: Solution becomes turbid/cloudy white
- Continuation: Precipitate may dissolve in excess CO₂
Explanation
Calcium hydroxide reacts with CO₂ to form calcium carbonate, an insoluble white precipitate. With excess CO₂, it converts to soluble calcium bicarbonate:
CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂
This is the most reliable and widely used test for CO₂ identification.
Burning Splint Test
Confirmation TestProcedure
- Light a wooden splint until it glows brightly
- Blow out the flame (glowing ember remains)
- Introduce the glowing splint into CO₂ gas
Observation
The glowing splint extinguishes immediately. No combustion occurs.
Explanation
CO₂ is an inert gas that does not support combustion. It lacks oxygen atoms that fuel burning. This demonstrates CO₂’s non-combustible nature and is used in fire extinguishers.
Sodium Hydroxide (NaOH) Test
Additional TestReactions
CO₂ + 2NaOH → Na₂CO₃ + H₂O
CO₂ + NaOH → NaHCO₃
Observation
No visible precipitate forms in NaOH solution. This differs from Ca(OH)₂, which gives a white precipitate.
Explanation
Unlike calcium carbonate (insoluble), sodium carbonate and sodium bicarbonate are both soluble in water, so no visible precipitate forms.
Note
This test is less conclusive for CO₂ identification compared to the lime water test. It’s primarily used in combination with other tests.
Safety Precautions & Laboratory Rules
⚗️ Chemical Safety
- Handle dilute HCl with care; always wear gloves and eye protection
- Add acid to water, never water to acid
- Avoid skin contact; wash immediately if exposed
- Use only in well-ventilated areas or fume hoods
- Keep away from bases and oxidizing agents
- Dispose of waste HCl according to lab regulations
🔬 Glassware Safety
- Inspect all glassware for cracks or damage before use
- Use rubber corks and connectors for gas setups
- Ensure delivery tubes are securely fitted
- Do not apply excessive force when connecting apparatus
- Use stands and clamps to secure flasks
- Allow hot glassware to cool before handling
👤 Personal Protective Equipment
- Safety goggles: Mandatory at all times
- Rubber gloves: Nitrile or latex, acid-resistant
- Lab coat: Fully buttoned, reaching below knees
- Closed-toe shoes: Non-slip, protect feet
- Long hair: Tied back securely
- No jewelry: Remove loose rings and bracelets
📋 General Laboratory Rules
- No eating, drinking, or smoking in the laboratory
- Know the location of safety equipment (first aid, eye wash, shower)
- Report all accidents and injuries to the instructor immediately
- Clean up spills immediately using appropriate materials
- Never work alone; always have supervision
- Follow the experimental procedure exactly as instructed
🚨 Emergency Procedures
- Chemical burn: Flush with water for 15 minutes; seek medical help
- Eye contact: Rinse immediately with eye wash; notify instructor
- Inhalation: Move to fresh air immediately; ventilate area
- Ingestion: Call poison control or emergency services
- Fire: Use appropriate extinguisher (not water for acid fires)
♻️ Proper Disposal
- All dilute HCl must go into the acid waste container
- Marble chip residue: collect and neutralize before disposal
- Calcium chloride solution: may be rinsed down the drain if neutralized
- Never mix chemical wastes unless instructed
- Label all waste containers clearly
Applications of Carbon Dioxide
Carbonated Beverages
Dissolved under pressure in soft drinks, sparkling water, and beer to create fizz. Typical carbonation: 3.5–4.0 volumes of CO₂.
Dry Ice
Solid CO₂ at -78.5°C freezes food, preserves samples, and creates fog effects. Sublimes directly to gas.
Fire Extinguishers
Type B and C extinguishers displace oxygen around flames. Effective on electrical and flammable-liquid fires.
Greenhouse Growth
Enriched CO₂ atmosphere (500–1500 ppm) enhances photosynthesis, increasing crop yield.
Industrial Processes
Used in welding (MIG/MAG), metal fabrication, and supercritical extraction.
Medical Applications
CO₂ laser surgery, laparoscopic insufflation, and blood-gas analysis.
Laboratory Uses
Preparation of carbonates, pH buffer systems, and inert atmosphere provision.
Environmental Science
Carbon cycle studies, atmospheric research, and ocean acidification monitoring.
Aerospace
Spacecraft life support systems and atmospheric simulation for extraterrestrial research.
Food Processing
Preservation, blanching, freezing, and controlled-atmosphere packaging.
Pharmaceutical Extraction
Supercritical CO₂ extraction for caffeine removal and essential oils.
Special Effects
Dramatic fog and mist effects using dry ice sublimation or CO₂ snow.
Environmental Significance of CO₂
Greenhouse Effect & Global Warming
Mechanism: CO₂ and other greenhouse gases trap heat from the sun in Earth’s atmosphere, preventing it from escaping to space.
Historical CO₂ levels:
- Pre-industrial (1750): ~280 ppm
- Year 2000: ~368 ppm
- Year 2020: ~413 ppm
- Recent: 420+ ppm
Consequences:
- Global average temperature rise (~1.1°C since pre-industrial)
- Melting of polar ice caps and glaciers
- Rising sea levels threatening coastal regions
- More extreme weather events
- Disruption of ecosystems and biodiversity loss
Ocean Acidification
Process: Atmospheric CO₂ dissolves in seawater, forming carbonic acid:
CO₂ (g) + H₂O (l) ⇌ H₂CO₃ (aq)
H₂CO₃ (aq) ⇌ H⁺ (aq) + HCO₃⁻ (aq)
Effects:
- Ocean pH has decreased by 0.1 units (~30% increase in acidity) since pre-industrial times
- Reduced carbonate ion availability damages shellfish and coral skeletons
- Threatens food chains and marine ecosystems
- Economic impacts on fisheries and aquaculture
Climate Change & CO₂
Role of CO₂: CO₂ is the primary greenhouse gas responsible for anthropogenic climate change.
Main sources of anthropogenic CO₂:
- Fossil fuel combustion: ~75% of total
- Deforestation and land-use changes: ~11%
- Industrial processes and cement production: ~14%
Mitigation strategies:
- Transition to renewable energy sources
- Improve energy efficiency in buildings and transport
- Reforestation and protection of forests (CO₂ sinks)
- Carbon capture and storage (CCS) technology
- International agreements (Paris Accord)
Industrial Preparation of CO₂
1. Limestone Decomposition
Process
CaCO₃ (s) → CaO (s) + CO₂ (g)
Temperature: 825–900°C in rotary kilns
Scale
Billions of tons annually — the main source of industrial CO₂.
Co-product
CaO (quicklime) is used to produce cement, mortar, and steel.
2. Ammonia Plant CO₂
Process
CH₄ + H₂O → CO + 3H₂
CO + H₂O → CO₂ + H₂
Application
Hydrogen for ammonia synthesis; CO₂ is a byproduct, captured and purified up to 99.5%.
3. Fermentation Industry
Source
Microbial fermentation of carbohydrates in breweries, wineries, and bioethanol plants.
Reaction
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
Recovery
Gas collected from fermentation tanks, cooled and compressed to food-grade purity.
4. Combustion & Flue Gas
Method
CO₂ recovered from exhaust gases of combustion processes.
Concentration
3–15% by volume in flue gas.
Challenge
Requires advanced separation technology; viable mainly at large scale.
5. Chemical Industry
Source
Byproduct from sodium carbonate (Solvay process) and methanol synthesis.
Purity
Often 99%+, ready for direct use or minimal processing.
6. Direct Air Capture
Method
Chemical sorbents or physical separation techniques pull CO₂ directly from air.
Current status
Emerging technology; still expensive (~$100–200/ton) but important for climate mitigation.
Knowledge Assessment
Multiple Choice Questions
Answer the following 10 questions to test your understanding of CO₂ preparation.
Practical Viva Questions
Prepare for your laboratory viva examination.
1. Why are marble chips and dilute HCl used for CO₂ preparation?
Answer: Marble chips (CaCO₃) are cheap, readily available, and solid. Dilute HCl reacts vigorously at room temperature without heating, and the reaction rate is controllable and safe.
Reaction: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂↑
2. Why is downward displacement used for collecting CO₂?
Answer: CO₂ (44 g/mol) is denser than air (≈29 g/mol), so it sinks and displaces air upward — allowing simple collection without water or special apparatus.
3. Why can’t we use water displacement for CO₂?
Answer: CO₂ is slightly soluble in water (1.45 g/L at 25°C) and dissolves to form carbonic acid instead of being collected as pure gas: CO₂ + H₂O → H₂CO₃. This causes incomplete collection and contaminated samples.
4. Explain the chemistry of the lime water test.
Procedure: Pass CO₂ through lime water, Ca(OH)₂.
Observation: The solution turns white and turbid; excess CO₂ may clear it again.
CO₂ + Ca(OH)₂ → CaCO₃↓ + H₂O, then with excess CO₂: CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂
5. Why does a burning splint extinguish in CO₂?
Answer: CO₂ is inert and does not support combustion — it has no oxygen available to sustain burning, so a glowing splint extinguishes on contact.
Summary & Revision Notes
Key Facts About CO₂
- Formula: CO₂ | Molar mass: 44.01 g/mol
- Colourless, odourless (slightly pungent at high conc.)
- Denser than air (1.98 kg/m³ vs 1.29 for air)
- Non-flammable, non-supporter of combustion
- Slightly soluble in water (forms H₂CO₃)
- Linear structure (O=C=O, sp hybridization)
Laboratory Preparation
- Reactants: Marble chips (CaCO₃) + dilute HCl
- Equation: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂↑
- Apparatus: Conical flask, thistle funnel, delivery tube, gas jar
- Collection: Downward displacement of air
- Purity: Approximately 95–98% at lab scale
Identification Tests
- Lime water: White turbidity → CaCO₃ precipitate
- Burning splint: Extinguishes (no combustion support)
- NaOH: No visible change (soluble carbonates)
- pH: Slightly acidic (forms H₂CO₃)
Chemical Properties
- Acidic oxide: reacts with bases to form carbonates
- With Ca(OH)₂: white CaCO₃ precipitate
- Reduced by hot carbon: C + CO₂ → 2CO
- Essential for photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Safety Reminders
- Always wear safety goggles and gloves
- Handle dilute HCl with care; never add water to acid
- Ensure all apparatus connections are secure
- Never point tubes at people or faces
- Report accidents immediately to the instructor
Important Applications
- Carbonated beverages (3.5–4.0 volumes of CO₂)
- Dry ice for refrigeration (-78.5°C)
- Fire extinguishers (Types B & C)
- Greenhouse gas enrichment for plant growth
- Medical applications (lasers, insufflation)
Environmental Significance
- Major greenhouse gas; atmospheric level: 420+ ppm
- Increased from ~280 ppm (pre-industrial)
- Responsible for ~1.1°C of global warming
- Causes ocean acidification (pH decrease of 0.1 units)
Industrial Preparation Methods
- Limestone decomposition: CaCO₃ → CaO + CO₂
- Ammonia synthesis: Byproduct from Haber-Bosch
- Fermentation: Microbial decomposition of sugars
- Direct air capture: Emerging DAC technology
Interactive Flashcards for Revision
Click the card to flip it
References & Further Reading
Textbooks
- NCERT Chemistry Class 10 & 12 (India)
- NEB Chemistry Textbook (Nepal)
- Cambridge IGCSE Chemistry
- GCSE Chemistry (AQA, Edexcel, OCR)
Scientific Journals
- Journal of Chemical Education
- Green Chemistry
- Environmental Science & Technology
- Nature Climate Change
Online Resources
- NIST Chemistry Database
- PubChem (NIH database)
- ScienceDirect
- MIT OpenCourseWare
Organizations
- IPCC
- NOAA
- IUPAC
- EPA
Disclaimer
This virtual laboratory is designed for educational purposes. For medical or industrial applications, consult official documentation and safety data sheets (SDS).
The simulations presented are simplified representations of real laboratory procedures. Always follow institutional safety protocols and instructor guidance when conducting actual experiments.