CHEM TEST Electrolysis + Chemical Analysis

Flashcards covering the topics of pure and impure substances, separation techniques (filtration, crystalisation, chromatography) and electrolysis.

Pure Substance

A substance that consists of a single element or compound and contains no other substances. It melts and boils at specific temperatures, not a range.

Impure Substance Melting/Boiling Point

On a graph, an impure substance would have curvy lines when representing melting and boiling points.

Filtration

A separation technique used to separate an insoluble solid from a solution (e.g., sand from a mixture of sand and water).

Residue

The insoluble solid (e.g., sand) that remains behind in the filter paper after filtration.

Filtrate

The solvent (e.g., water) that passes through the filter paper during filtration.

Crystallisation

A separation technique used to separate a soluble solid from a solution (e.g., copper sulphate from a solution of copper (II) sulphate in water).

Chromatography

A technique used to separate and identify a mixture of liquids. It separates substances based on their solubility in a solvent.

Rf Value

In chromatography, the distance travelled by the component divided by the distance travelled by the solvent.

Mobile Phase

In chromatography, the phase that moves, usually the solvent.

Stationary Phase

In paper chromatography, the paper which does not move.

Pure Substance (Chromatography)

In chromatography, produces a single spot.

Mixture of Compounds (Chromatography)

In chromatography, produces more than one spot.

Electrolysis

Using electricity to breakdown compounds; the substance must be molten or aqueous, and a DC current is used.

Electrolyte

The substance that gets broken down during electrolysis; it is an ionic compound.

Anode

The positive electrode in electrolysis; it attracts negative anions. Negative non-metal ions form molecules at the anode.

Cathode

The negative electrode in electrolysis; it attracts positive cations. Metal cations form atoms at the cathode.

Test for Carbon Dioxide

Lime water turns cloudy in the presence of carbon dioxide.

Cryolite in Aluminium Electrolysis

Added to aluminum oxide to lower its very high melting point, reducing energy consumption and costs.

Positive Electrode Replacement (Aluminium Electrolysis)

The positive electrode, typically made of carbon, needs to be replaced because it gradually consumed due to the oxidation of the electrode material reacting with oxygen produced during electrolysis.

Electrolysis of Aqueous Solutions (Anode)

At the anode, a non-metal (from ionic compound) or oxygen (from OH- ions in the water) will form.

Electrolysis of Aqueous Solutions (Cathode)

At the cathode, a metal (from ionic compound) or hydrogen (from H+ ions in water) will form.