Module 2: Definitions Flashcards
Define relative formula mass.
The weighted mean mass of the formula unit of a compound compared with one-twelfth of the mass of an atom of carbon-12.
Define relative atomic mass.
(Ar)
The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12.
Define relative isotopic mass.
The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon-12.
Define relative molecular mass.
(Mr)
The weighted mean mass of a molecule of a compound compared with one-twelfth of the mass of an atom of carbon-12
What is an ionic bond?
Electrostatic force of attraction between cations and anions.
What is a metallic bond?
Electrostatic attraction between cations (positive metal ions) and delocalised electrons.
What is a covalent bond?
Strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
What are isotopes?
Atoms of the same element with different numbers of neutrons and different masses.
What are IMF’s?
Intermolecular force.
An attractive force between molecules. Intermolecular forces can be London forces, permanent dipole-dipole interactions or hydrogen bonding.
What is a hydrogen bond?
A strong dipole-dipole attraction between an electron-deficient hydrogen atom of -NH, -OH or HF on one molecule and a lone pair of electrons on a highly electronegative atom containing N, O or F on a different molecule.
What is the empirical formula?
The formula that shows the simplest whole-number ratio of atoms of each element present in a compound.
What is the molecular formula?
A formula that shows the number and type of atoms of each element present in a molecule.
Define stoichiometry.
The ratio of the amount, in moles, of each substance in a chemical equation (essentially the ratio of the balancing numbers).
Define anhydrous.
Containing no water molecules.
Define hydrated.
A crystalline compound containing water molecules.
Define water of crystallisation.
Water molecules that are bonded into a crystalline structure of a compound.
Define dative covalent.
A shared pair of electrons in which the bonding pair has been provided by one of the bonding atoms only; also called a coordinate bond.
What is Avogadro’s constant?
(Na)
The number of atoms per mile of the carbon-12 isotope.
6.02x10^23 mol^-1
Define molar mass.
(M)
The mass per mole of a substance, in units of gmol^-1.
What is molar gas volume?
(Vm)
The volume per mole of gas molecules at a stated temperature and pressure.
What is a mole?
The amount of any substance containing as many elementary particles as there are carbon atoms in exactly 12g of the carbon-12 isotope, that is, 6.02x10^23 particles.
What is percentage yield?
% yield =
actual amount of product (mol)
__________________________________
theoretical amount of product (mol)
X100
Define atom economy.
Sum of molar masses of desired products
/ divided by
Sum of molar masses of all products
Å ~ 100
What is sustainability?
Carrying out chemical processes without depleting the Earth’s natural resources or damaging the environment.
What is an acid?
A species that releases H+ ions in aqueous solution.
What is a base?
A compound that neutralises an acid to form a salt.
What is an alkali?
A type of base that dissolves in water to release hydroxide ions, OH- (aq).
What is a weak acid?
An acid that dissociates only partially in solution.
What is a strong acid?
An acid that dissociates completely in solution.
What is a salt?
The product of a reaction in which the H+ ions from the acid are replaced by metal or ammonium ions.
Define oxidation.
Loss of electrons or an increase in oxidation number.
Define reduction.
Gain of electrons or decrease in oxidation number.
What is a redox reaction?
A reaction involving both reduction and oxidation.
What is an oxidising agent?
A reagent that oxidises (takes electrons from) another species.
What is a reducing agent?
A reagent that reduces (adds electrons to) another species.
What is a shell (electron shell)?
A group of atomic orbitals with the same principal quantum number n. Also known as a main energy level.
What is a subshell?
A group of orbitals of the same type within a shell.
What is an orbital?
A region of space around the nucleus that can hold up to two electrons as long as their spins are paired (opposite spins).
Define electronegativity.
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.
What are polar molecules?
A molecule with an overall dipole, having taken into account any dipoles across bonds and the shape of the molecule.
