Definitions Flashcards
What is a transitional element?
It is a d-block element that can form one or more stable ions with a partially-filled d-orbital sub shell
What is a complex?
A molecule or ion formed by a central metal atom or ion surrounded by one or more ligands
What do you call: an ion or molecule that has one or more lone pairs of electrons available to be donated into the vacant orbitals of the metal atom or ion?
A ligand
Define ‘catalyst’
A catalyst is a substance that increases the rate of reaction by providing an alternative pathway of lower activation energy and the catalyst does not undergo any permanent chemical changes
Define: Standard Enthalpy Change of Reaction
Molar quantities of reactants as specified by the chemical equation to form products at STANDARD CONDITIONS
What are the Standard Conditions?
- 298K (or 25 degrees Celcius) temperature
- 1 bar (100,000 Pa) pressure
- 1 mol dm^-3 concentration
Define: SEC of Formation
1 mole of substance formed from its constituent elements in their standard states at SC
Define: SEC of Combustion
Heat evolved when 1 mole of a substance is completely burnt in excess oxygen gas at SC
What is SEC of neutralisation
Heat evolved when 1 mole of water is formed in the neutralisation reaction between an acid and a base at SC
Define Bond Energy
Energy required to break 1 mole of a covalent bond in the gaseous state
Define SEC of Atomisation
- Energy required when 1 mole of gaseous atoms is formed from the element at SC
- Energy required when 1 mole of the compound is converted into gaseous atoms at SC
What is SEC of hydration
Heat evolved when 1 mole of free gaseous ions is dissolved into an infinite volume of water at SC
What is SEC of solution
Enthalpy change when 1 mole of solute is completely dissolved into an infinite volume of solvent at SC
What is Lattice energy
Heat evolved when 1 mole of solid ionic compound is formed from its constituent gaseous ions
What is Ionisation Energy?
Energy required to remove 1 mole of electrons from gaseous (WHAT SPECIES. Is it atoms or ions) to form 1 mole of gaseous (WHAT CHARGED?) cations.
Define Electron Affinity
Enthalpy change when 1 mole of electrons is added to 1 mole of gaseous (WHAT?) to form 1 mole of gaseous (What anions?)
What is entropy change?
Measure of randomness or disorder in a system reflected in the number of ways that the energy of a system is distributed through the motion of particles
Define the Gibbs free energy change
Gibbs free energy change needed to convert reactants into products at SC
Definition of a ligand
an ion or molecule that has one or more lone pairs of electrons available to be donated into the vacant orbitals of the metal atom or ion
Why are transitional element complexes coloured?
- In the presence of ligands, partially filled 3d orbitals of a TM ion are split into two different energy levels with a small energy gap between them
- There are vacancies in the higher energy d orbitals
- Promotion of an electron from lower to the higher of these d orbitals requires the absorption of radiation in the visible electromagnetic spectrum with energy corresponding to the energy gap
- Such a d-d transition is responsible for the colour of the complex ion where the colour observed is the complement to the colour absorbed
