OCR A-Level Chemistry: Definitions Part 2
This flashcard set explains key terms related to atomic structure, including the definitions of isotopes, atomic and mass numbers, ions, and relative isotopic mass. It provides foundational knowledge essential for understanding atomic theory and chemical calculations.
Catalyst
A substance that increases the rate of a chemical reaction without being used up in the process
Key Terms
Catalyst
A substance that increases the rate of a chemical reaction without being used up in the process
Activation Energy
The minimum energy required to start a reaction by the breaking of bonds
Dynamic Equilibrium
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentration...
Le Chatelier's Principle
When a system in dynamic equilibrium is subjected to external change, the system readjusts itself to minimise the effect of the change and restore ...
Closed Systen
A system isolated from its surroundings
Equilibrium Constant
A measure of the position of equilibrium
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| Term | Definition |
|---|---|
Catalyst | A substance that increases the rate of a chemical reaction without being used up in the process |
Activation Energy | The minimum energy required to start a reaction by the breaking of bonds |
Dynamic Equilibrium | The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentrations do not change |
Le Chatelier's Principle | When a system in dynamic equilibrium is subjected to external change, the system readjusts itself to minimise the effect of the change and restore equilibrium |
Closed Systen | A system isolated from its surroundings |
Equilibrium Constant | A measure of the position of equilibrium |
Homogeneous | In the same phase |
Heterogeneous | Different phases |
Collision Theory | Two reacting particles must collide for a reaction to occur, and must be in the correct orientation and have sufficient energy to overcome the activation energy of the reaction |
Half Life | The time taken for the concentration of the reactant to be reduced by half |
Reaction Mechanism | A series of steps that together make up the overall reaction |
Rate Determining Step | The slowest step in the reaction mechanism of a multi step reaction |
Mole Fraction | Number of mole of species / total number of moles of all species |
Partial Pressure | Mole fraction x total pressure |
Lattice Enthalpy | The change in enthalpy that accompanies the formation of one mole of ionic compound from its gaseous ions under standard conditions |
Standard Enthalpy Change of Atomisation | The change in enthalpy that accompanies the formation of one mole of gaseous atoms from the element in the standard state |
First Electron Affinity | The change in enthalpy that accompanies the formation of one mole of gaseous 1- ions from gaseous atoms |
Standard Enthalpy Change of Solution | The enthalpy change that takes place when one mole of a compound is completely dissolved in water under standard conditions |
Standard Enthalpy Change of Hydration | The enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aqeuous ions under standard conditions |
Standard Entropy | The quantitative measure of the degree of disorder in a system |
Standard Entropy Change of Reaction | The entropy change that accompanies a reaction in the molar quantities expressed in the chemical equation under standard conditions, all reactants and products being in their standard states |
Free Energy Change | The balance between enthalpy, entropy and temperature for a process |
Redox | A reaction in which both reduction and oxidation take place |
Standard Electrode Potential | The emf of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1 mol/dm^3 and a gas pressure of 1 atm |
Brønsted-Lowry Acid | It accepts a proton |
Brønsted-Lowry Base | It donates a proton |
Conjugate Acid | Brønsted-Lowry base that accepted a proton |
Conjugate Base | Brønsted-Lowry acid that donated a proton |
Acid Dissociation Constant | The equilibrium constant that shows the extended of dissociation of a weak acid |
| -log(10)[H+] |
Weak Acid | Partial dissociation of hydrogen atoms |
Strong Acid | Complete dissociation of hydrogen atoms |
Ionic product of water | Kw = [H+][OH-] |
Buffer Solution | A system that minimises pH changes on addition of small amounts of an acid or a base |
Transition Metal | A d-block element that forms an ion with an incomplete d sub-shell |
Complex Ion | A transition metal ion bonded to ligands by coordinate bonds (dative covalent bonds) |
Coordination Number | The number of coordinate bonds attached to the central metal ion |
Ligand | A molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond |
Denticity | The number of separate sites in a molecule or ion that can donate an electron pair to a transition metal ion |
Monodentate | A ligand that can donate one electron pair to a transition metal ion |
Bidentate | A ligand that can donate two electron pairs to a transition metal ion |
Tridentate | A ligand that can donate three electron pairs to a transition metal ion |
Stereoisomerism | Species with the same structural formula but with a different arrangement in space |
Optical Isomers / Enantiomers | Non-super imposable mirror images of each other |
Ligand Substitution | A reaction in which one or more ligands in a complex ion are replaced by different ligands |