Chemistry EA

Dynamic equilibrium

The state in a closed system where the forward and reverse reactions occur at equal rates, so the concentrations of reactants and products remain constant

Le Châtelier's principle

When a system at equilibrium is disturbed, it shifts to partially oppose the disturbance and establish a new equilibrium

Closed system

A system that can exchange energy but not matter with its surroundings

Equilibrium constant (Kc)

The ratio of equilibrium concentrations of products to reactants, each raised to the power of their coefficients

Reaction quotient (Q)

A value calculated using current concentrations to predict the direction a reaction will proceed to reach equilibrium

Catalyst

A substance that increases the rate of both the forward and reverse reactions equally without changing the equilibrium position or Kc

Collision theory

The theory that reactions occur when particles collide with sufficient energy and correct orientation

Activation energy

The minimum energy required for a successful collision to produce a reaction

Increasing reactant concentration

Shift towards products

Decreasing reactant concentration

Shift towards reactants

Increasing product concentration

Shift towards reactants

Decreasing product concentrations

Shift towards products

Increasing pressure/decreasing volume

Shift toward side with fewer moles of gas

Decreasing pressure/increasing volume

Shift toward side with more moles of gas

Adding catalyst

No shift in equilibrium, but reaction rates increase

Increasing temperature

Shifts toward endothermic reaction

Decreasing temperature

Shifts toward exothermic reaction

Only factor that changes equilibrium constant

Temperature

Arrhenius acid

A substance that produces H⁺ ions in aqueous solution

Arrhenius base

A substance that produces OH⁻ ions in aqueous solution

Brønsted–Lowry acid

A proton (H⁺) donor

Brønsted–Lowry base

A proton (H⁺) acceptor

Conjugate acid

The species formed when a base gains a proton

Conjugate base

The species formed when an acid loses a proton

Conjugate acid–base pair

Two species that differ by one proton (H⁺)

Amphiprotic species

A species that can both donate and accept a proton

Amphoteric substance

A substance that can act as both an acid and a base

Strong acid/base

Completely ionises in water

Weak acid/base

Only partially ionises in water

Ionisation

The formation of ions when a substance dissolves or reacts in water

Dissociation

The separation of an ionic compound into its ions in solution

Acid dissociation constant (Ka)

The equilibrium constant for the ionisation of a weak acid

Higher Ka means stronger acid

Base dissociation constant (Kb)

The equilibrium constant for the ionisation of a weak base

Higher Kb means stronger base

Ionic product of water (Kw)

The equilibrium constant for the self-ionisation of water

Neutralisation

A reaction between an acid and a base producing water and a salt

Buffer solution

A solution that resists changes in pH when small amounts of acid or base are added

Indicator

A weak acid or base whose colour changes over a specific pH range

End point

The point in a titration where the indicator changes colour

Equivalence point

The point in a titration where the amount of acid equals the amount of base according to the reaction stoichiometry

Titration

An analytical technique used to determine the concentration of an unknown solution using a standard solution

Aliquot

A measured portion of solution used during a titration

Titre

The volume of solution delivered from a burette during a titration

Redox reaction

A chemical reaction in which oxidation and reduction occur simultaneously through the transfer of electrons

Oxidation

The loss of electrons, resulting in an increase in oxidation number

Reduction

The gain of electrons, resulting in a decrease in oxidation number

Oxidising agent

A species that causes oxidation by accepting electrons and is itself reduced

Reducing agent

A species that causes reduction by donating electrons and is itself oxidised

Disproportionation

A redox reaction in which the same species is both oxidised and reduced

Oxidation Number Rules

• An element in its standard state has an oxidation number of 0.

• A monatomic ion has an oxidation number equal to its charge.

• Group 1 metals always have an oxidation number of +1.

• Group 2 metals always have an oxidation number of +2.

• Aluminium always has an oxidation number of +3.

• Fluorine always has an oxidation number of −1.

• Hydrogen is usually +1, but is −1 in metal hydrides.

• Oxygen is usually −2, but is −1 in peroxides.

• Chlorine, bromine and iodine are usually −1 unless bonded to oxygen or fluorine.

• The sum of oxidation numbers in a neutral compound is 0.

• The sum of oxidation numbers in a polyatomic ion equals the ion's overall charge.

Galvanic (voltaic) cell

An electrochemical cell that produces electrical energy from a spontaneous redox reaction

Electrolytic cell

An electrochemical cell that uses electrical energy to drive a non-spontaneous reaction

Standard electrode potential (E°)

The reduction potential of a half-cell measured relative to the standard hydrogen electrode

Anode

The electrode where oxidation occurs

Cathode

The electrode where reduction occurs

Salt bridge

A device containing an electrolyte that allows ions to flow between half-cells while maintaining electrical neutrality

Electrolyte

A substance containing mobile ions that conducts electricity when molten or dissolved

Electroplating

The process of coating an object with a thin layer of metal using electrolysis

Electrorefining

The purification of metals by electrolysis

Molten electrolyte

An ionic compound melted so its ions are free to move

Aqueous electrolyte

An ionic solution in which ions are dissolved in water

Anode and Cathode charge in Galvanic Cell

Negative Anode, Positive Cathode

Anode and Cathode charge in Electrolytic Cell

Positive Anode, Negative Cathode (PANIC)

Faraday constant (F)

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Faraday's First Law

The mass of substance produced during electrolysis is proportional to the charge passed

Faraday's Second Law

The mass deposited depends on the number of electrons required in the reaction

Organic compound

A compound that contains carbon atoms bonded to hydrogen and often other elements such as oxygen, nitrogen or halogens

Homologous series

A family of organic compounds with the same functional group, similar chemical properties and successive members differing by CH₂

Functional group

The atom or group of atoms responsible for the characteristic chemical reactions of an organic compound

Alkane

A saturated hydrocarbon containing only single C–C bonds

Alkene

An unsaturated hydrocarbon containing at least one C=C double bond

Alkyne

An unsaturated hydrocarbon containing at least one C≡C triple bond

Haloalkane

An alkane in which one or more hydrogen atoms have been replaced by a halogen atom

Alcohol

An organic compound containing a hydroxyl (-OH) functional group

Primary, Secondary, Tertiary

Primary: Functional group attached to one carbon

Secondary: Functional group attached to two carbons

Tertiary: Functional group attached to three carbons

Aldehyde

An organic compound containing the terminal -CHO functional group

Ketone

An organic compound containing a carbonyl (C=O) group bonded to two carbon atoms

Carboxylic acid

An organic compound containing the carboxyl (-COOH) functional group

Ester

An organic compound containing the ester (-COO-) functional group

Amine

An organic compound derived from ammonia in which one or more hydrogen atoms are replaced by carbon-containing groups

Amide

An organic compound containing the -CONH₂ (or substituted) functional group

Addition polymer

A polymer formed from alkene monomers without producing a small molecule

Condensation polymer

A polymer formed while eliminating a small molecule such as water

Structural formula

A formula showing the arrangement and bonding of atoms in a molecule

Condensed structural formula

A shortened structural formula showing the arrangement of atoms with minimal bond lines

Skeletal formula

A simplified representation showing only the carbon skeleton and functional groups

Molecular formula

A formula showing the actual number of each type of atom in a molecule

Empirical formula

The simplest whole-number ratio of atoms in a compound

Isomer

One of two or more compounds with the same molecular formula but different structures or spatial arrangements

Structural isomer

An isomer with a different arrangement of atoms

Stereoisomer

Compounds with the same molecular formula and structural formula but a different three-dimensional arrangement of atoms.

Optical isomer

A stereoisomer that is a non-superimposable mirror image of another molecule (an enantiomer)

Chiral carbon

A carbon atom bonded to four different atoms or groups

Geometric isomer

A stereoisomer caused by restricted rotation around a carbon–carbon double bond or within a ring structure

Cis isomer

A geometric isomer in which identical or similar groups are on the same side of the double bond or ring

Trans isomer

A geometric isomer in which identical or similar groups are on opposite sides of the double bond or ring

Addition reaction

A reaction in which atoms are added across a carbon–carbon double or triple bond

Addition polymerisation

Polymer formation by joining unsaturated monomers without producing a small molecule

Substitution reaction

A reaction in which one atom or group of atoms is replaced by another

Elimination reaction

A reaction in which atoms are removed from adjacent carbon atoms to form a multiple bond

Condensation reaction

A reaction in which two molecules combine to form a larger molecule while producing a small molecule such as water