Lab Equipment and Techniques

Lab Equipment

Pipette:
- Accurately measures liquid volumes (up to 25 cm $^3$ ).
- More accurate than measuring cylinders, but slower.
Burette:
- Accurately measures liquid volumes (up to 50 cm $^3$ ).
- More accurate than measuring cylinders, but slower.
Measuring Cylinder:
- Measures liquid volumes (25 cm $^3$ - 250 cm $^3$ ).
- Easy and quick, but not accurate.
Conical Flask:
- Holds and measures chemical liquid samples for heating, mixing, and boiling.
- Easy to mix.
Beaker:
- Stores, mixes, stirs, pours, heats, and transports liquids.
- Difficult to swirl/mix/shake compared to conical flasks.
Dropper (Teat pipette):
- Adds liquid in drops.
Gas jar:
- Collects gases.
Trough:
- Holds liquid (water) for collecting pure gas samples over water.
Wash bottle:
- Rinses laboratory glassware or washes salts to remove impurities.
Mortar & pestle:
- Grinds/crushes solid substances into smaller pieces (powder).
Lid:
- Melts or heats solid chemicals over a burner at high temperatures.
Crucible:
- Melting or heating solid chemicals over a burner at a very high temperature
Stand with clamp:
- Supports and holds glassware at variable heights.
Round bottomed flask:
- Heating and boiling liquids in distillation or reactions.
Flat bottomed flask:
- Heating and boiling liquids in distillation or reactions.
- Less durable than round bottom flasks.
Volumetric flask:
- Prepares solutions accurately to a known, specific volume.
Gas syringe:
- Collects & measures the volume of a gas.
Evaporating dish:
- Heats solutions to allow evaporation.
Thermometer:
- Measures temperature of solid, liquid and gas.
Watch glass:
- For evaporation; used as a lid for flasks and beakers.
Top pan balance:
- Measures mass of substances accurately.
Stopwatch:
- Measures time taken.
Stopper cork/Bung:
- Seals openings of glassware to prevent gas escape or fluid passage.
Gauze:
- Spreads heat for even heating.
Tripod:
- Supports devices above a Bunsen burner.
Bunsen burner:
- Produces flame for heating.
Funnel:
- Separates insoluble solids from liquids using filter paper.
Separating funnel:
- Separates immiscible liquids of different densities.
Stirring rod / Glass rod:
- Stirring / mixing chemicals
Test tube:
- Stores, mixes, and heats small amounts of chemicals.
Test tube holder:
- Holds test tubes while heating.
Test tube rack:
- Holds multiple test tubes upright.
Condenser:
- Cools and condenses vapor into liquid.
Thistle funnel:
- Adds small liquid volumes to an exact position.
Metallic tong:
- Holds hot crucibles, flasks, evaporating dishes, or small beakers.
Spatula:
- Transfers small quantities of solid substances.
Knife:
- Cuts soft metals (group 1).
Spirit burner:
- Heating, combustion, and sterilizing; uses alcohol fuel.
Fractionating column:
- Separates liquid mixtures into components based on volatility.
U-tube:
- Measures liquid pressure; cools steam to produce water.
Delivery tube:
- Allows gas to pass between containers.
Boiling tube:
- Heats and boils small liquid quantities; wider and thicker than test tubes.
Filter tube:
- Passes gas through a liquid.
Tap funnel:
- Used to separate immiscible liquids.
Goggles:
- Protects eyes from particles or dangerous materials.

Separation Techniques

Filtration:
- Separates insoluble solid from a liquid by dissolving the mixture and pouring through a filter funnel; residue (solid) and filtrate (soluble) obtained.
Crystallization:
- Obtains soluble solid from water as crystals by half evaporation, cooling, filtering, and drying.
Simple Distillation:
- Separates soluble solid from a liquid by boiling the mixture and condensing the vapor.
Fractional Distillation:
- Separates miscible liquids with different boiling points by heating and collecting fractions.
- Use electrical heater for flammable liquids.
Separating Funnel:
- Separates immiscible liquids by settling layers and draining.
Chromatography:
- Separates dissolved solids using chromatography paper and solvent.
- $R_f = \frac{\text{Distance moved by the substance}}{\text{Distance moved by the solvent front}}$
Purity is indicated by one spot on chromatography.

Electrolysis

Breaks down ionic compounds using electricity in molten or aqueous solutions.
Concentrated Solutions: Less reactive ions discharged.
Diluted Solutions: Water is electrolyzed, producing H $^+$ and OH $^-$ ions.
Electroplating: Coating a metal key with silver (key as cathode, silver as anode).

Acids and Bases

Acid:
- Produces H $^+$ ions in water, turns litmus red, pH < 7.
Base:
- Produces OH $^-$ ions in water, turns litmus blue, pH > 7.
Strength measured by universal indicator, pH meter, reaction with metal carbonates, and electrical conductivity.
Indicators: Litmus paper, methyl orange, and phenolphthalein.

Reaction of Metals

With acids: Produces salt and hydrogen (more reactive metals).
With metal carbonates: Produces salt, water, and carbon dioxide
With water: Produces metal hydroxide and hydrogen (most reactive metals).
With oxygen: Produces metal oxide.
Reducing copper oxide: CuO + H $<em>2$ -> Cu + H $</em>2$ O.
Reactivity order: K > Na > Ca > Mg > Zn > Fe > H

Rate of Chemical Reactions

Affected by temperature, pressure, concentration, surface area, stirring, catalyst, and light.

Preparation of Salts

Solubility rules applied to neutralization, titration, and precipitation methods.
- All group 1 and ammonium salts are soluble
- All nitrates are solube
- Chlorides are soluble except silver and lead chlorides
- Sulphates are soluble except barium, lead, and calcium sulfates
- Carbonates are insoluble except Sodium and potassium (Group 1) Ammonium Carbonates
- Oxides are insoluble except sodium, potassium, magnesium and calcium oxide
Neutralization: Reacting excess solid with acid, filtering, evaporating, and crystallizing.
Titration: Reacting acid and alkali with an indicator, then repeating without the indicator to prepare the salt, followed by evaporation and crystallization.
Precipitation: Mixing two soluble salts to form an insoluble salt, filtering, washing, and drying.

Colors

Metals: Silvery grey except Gold (Yellow) and Copper (Red brown).
Non-metals exhibit various colors (e.g., Sulfur - Yellow, Bromine - Reddish brown).

Anions and Cations

Tests for anions (iodide, bromide, chloride, sulfate, sulfite, nitrate, carbonate) involve specific reagents and observations.
Tests for cations (ammonium, chromium, copper, iron, zinc, aluminium, calcium) with sodium hydroxide and ammonia yield characteristic precipitates.
Flame Test: Metal ions produce distinct flame colors (e.g., Sodium - Yellow, Lithium - Red).

Test for gases

Hydrogen - Pops with lighted splint
Oxygen - Relights glowing splint
Carbon dioxide - Turns lime water milky
Chlorine - Bleaches litmus paper
Ammonia - Turns red litmus paper blue
Sulfur dioxide - Turns acidified potassium manganate VII from purple to colorless

Experimental Precautions

Acids: Add acid to water, not the other way around.
Handle concentrated acids in a fume cupboard.
Wear eye protection and gloves.