Experimental Chemistry and Separation Techniques

Comprehensive practice flashcards covering laboratory apparatus, physical quantities, methods of gas collection/drying, and separation techniques in chemistry.

Accuracy and Reliability

Concepts ensured by using appropriate apparatus; measurements should be recorded to half the smallest division, and final calculations left to $3$ significant figures.

Burette Measurement Precision

Volume of liquids measured in a burette should be recorded to $2$ decimal places.

SI Unit of Time

The Second ($s$); where $1\text{ h} = 60\text{ min} = 3600\text{ s}$; mechanical or analogue stopwatches have a smallest division of $0.1\text{ s}$.

SI Unit of Temperature

The Kelvin ($K$); calculated as $K = \text{°C} + 273$.

Data Loggers

Devices connected to temperature sensors or probes that record data continuously, save data, and produce graphs or charts.

SI Unit of Length

The metre ($m$); where $1\text{ m} = 10\text{ dm} = 100\text{ cm} = 1000\text{ mm}$.

SI Unit of Mass

The kilogram ($kg$); where $1\text{ tonne (t)} = 1000\text{ kg} = 1\text{ million g}$.

SI Unit of Volume

The cubic metre ($m^3$); where $1\text{ dm}^3 = 1000\text{ cm}^3$ and $1\text{ m}^3 = 1000000\text{ dm}^3$.

Volumetric Flask

Apparatus used for dilution in preparing solutions; used to measure a specific fixed volume.

Pipette

Apparatus used to measure a fixed volume with a range usually spanning $10\text{ cm}^3$ to $50\text{ cm}^3$; recorded to $1$ decimal place.

Meniscus Curve

The curve formed at the surface of a liquid; eyes should be positioned at this curve to avoid parallax error.

Gas Syringe

Apparatus used to measure gas volumes up to $100\text{ cm}^3$; it cannot be used to measure liquids.

Downward Delivery (Upward Displacement)

A method used to collect gases that are more dense than air (e.g., chlorine, hydrogen chloride, carbon dioxide, sulfur dioxide).

Upward Delivery (Downward Displacement)

A method used to collect gases that are less dense than air (e.g., ammonia, hydrogen).

Collection over water (Displacement of Water)

A method used to collect gases that are insoluble or slightly soluble in water (e.g., oxygen, hydrogen, carbon dioxide).

Concentrated Sulfuric Acid

A drying agent used specifically for drying acidic and neutral gases.

Quicklime (Calcium Oxide)

A basic drying agent used for drying basic and neutral gases (e.g., ammonia).

Fused Calcium Chloride

A drying agent used for most gases except ammonia, as it reacts with ammonia.

Sublimation

The process where a substance changes from a solid directly to a gaseous state without entering a liquid state (e.g., iodine, dry ice, ammonium chloride).

Filtration

A technique used to separate an insoluble solid from a liquid; the solid left behind is the residue and the liquid that passes through is the filtrate.

Evaporation to Dryness

A technique to separate a dissolved solid from its solvent by heating until all solvent has vaporized; used for substances that do not decompose.

Crystallisation

A technique to obtain a pure solid from its saturated solution, preferred for substances that are not stable to heat or decompose when heated.

Simple Distillation

Used to separate a pure solvent (liquid) from a solution; involves vaporizing the liquid and collecting it via condensation.

Boiling Chips

Small pieces added to a distillation flask to ensure smooth boiling.

Miscible Liquids

Liquids that form a uniform (homogeneous) solution when mixed together (e.g., ethanol and water).

Immiscible Liquids

Liquids that form a heterogeneous mixture and separate into distinct layers based on density when left undisturbed (e.g., oil and water).

Separating Funnel

Apparatus used to separate immiscible liquids by removing the densest layer through a tap at the bottom.

Chromatography

A technique used to separate a mixture of substances based on their different solubilities in a given solvent.

Solvent Front

The final position reached by the solvent on chromatography paper.

Locating Agents

Chemicals used to react with colourless substances on a chromatogram to form coloured spots.

$R_f$ Value (Retention Factor)

The ratio of the distance travelled by the substance to the distance travelled by the solvent front.

Fractional Distillation

A technique used to separate miscible liquids with different boiling points using a fractionating column containing glass beads.

Pure Substance

A substance consisting of only one element or compound with a specific melting and boiling point under fixed conditions.

Effect of Impurities

Impurities lower the melting point and raise the boiling point of a substance, causing it to melt or boil over a range of temperatures.