Rucete ✏ SAT Chemistry In a Nutshell
15. The Laboratory
This chapter focuses on lab safety, equipment, experiment setups, and qualitative testing. These skills are often tested on the SAT Chemistry exam and are critical for performing and analyzing lab experiments properly.
Essential Lab Skills for SAT Chemistry
- Understand and explain lab safety rules and procedures
- Identify and correctly use common lab equipment
- Interpret lab data and observations to reach valid conclusions
Microscale and Technological Tools
- Microscale labs: use smaller amounts of chemicals
- Reduce cost and waste
- Are safer to use
- Modern tools include:
- Gravimetric balance: precise to 0.001 g
- pH meters: provide digital pH readings
- Spectrophotometer: measures light absorbance to determine molarity
- Computer-assisted labs: use probes to graph temperature, pressure, etc.
Ten Commandments of Lab Safety
- Dress properly: goggles, apron, tied hair, closed shoes
- Know how to use safety equipment: eyewash, fire blanket, extinguisher, shower
- Read labels carefully; never taste or sniff chemicals
- Dispose of chemicals as directed; don’t return unused chemicals
- Add acids/bases to water slowly—never the reverse
- Don’t point test tubes at people when heating
- Never pipette by mouth—use a bulb or pipette aid
- Use a fume hood for toxic gases
- No eating or drinking in the lab
- Follow all directions; don’t mix chemicals randomly
Common Lab Setups and Experiments
- Gas Collection:
- Collect H₂, O₂, CO₂ over water using a eudiometer
- Volume measured by displacement of water
- Chromatography:
- Separates substances based on movement through a medium
- Paper chromatography separates pigments or inks
- Rf = distance by substance ÷ distance by solvent
- Electrochemical Cells:
- Voltaic cells generate electricity via redox
- Use salt bridge and two metal half-cells
- Voltmeters measure potential difference
Qualitative Tests: Gases
- Hydrogen (H₂): pops when ignited
- Oxygen (O₂): reignites glowing splint
- Carbon dioxide (CO₂): turns limewater cloudy
- Ammonia (NH₃): sharp smell, red litmus turns blue
- Chlorine (Cl₂): green-yellow, bleaches litmus
- Hydrogen sulfide (H₂S): rotten egg smell, forms metal sulfides
Qualitative Tests: Anions
- Carbonate (CO₃²⁻): add acid → bubbles CO₂
- Sulfate (SO₄²⁻): add BaCl₂ → white precipitate
- Chloride (Cl⁻): add AgNO₃ → white ppt (soluble in NH₃)
- Nitrate (NO₃⁻): add FeSO₄ + H₂SO₄ → brown ring at interface
Qualitative Tests: Cations
- Ammonium (NH₄⁺): base + heat → NH₃ gas (red litmus turns blue)
- Iron (Fe²⁺ / Fe³⁺):
- Fe²⁺ + OH⁻ → green precipitate
- Fe³⁺ + OH⁻ → reddish-brown precipitate
- Copper (Cu²⁺):
- Blue solution
- Cu²⁺ + OH⁻ → blue precipitate
- Zinc (Zn²⁺):
- White precipitate with OH⁻
- Dissolves in excess OH⁻ (amphoteric)
Flame Tests (Metal Ions)
- Li⁺: crimson red
- Na⁺: intense yellow
- K⁺: violet (use cobalt glass)
- Ca²⁺: orange-red
- Sr²⁺: bright red
- Ba²⁺: pale green
- Cu²⁺: blue-green
In a Nutshell
The laboratory is where chemistry comes to life. This chapter covers everything from proper safety and equipment use to gas collection, electrochemical experiments, and qualitative analysis of common ions and gases. These practical skills are essential for both SAT Chemistry and real-world scientific investigation.