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CAPE U1 chemistry
Definitions
| Term | Definition |
|---|---|
| Isotopes | Isotopes are atoms with the same atomic number but different mass numbers. |
| Mass Number | Mass number (A) is the number of protons plus neutrons in the nucleus of an atom. |
| Atomic number | Atomic number (Z) is the number of protons in the nucleus of an atom. |
| Relative atomic mass | Relative atomic mass (Ar) is the weighted average mass of naturally occurring atoms of an element on a scale where an atom of 12C has a mass of exactly 12 units |
| Relative isotopic mass | Relative isotopic mass is the mass of a particular isotope of an element on a scale where an atom of 12C has a mass of exactly 12 units. |
| Radioactive isotopes | Isotopes of some elements have nuclei which break down (decay) spontaneously. These are described as radioactive isotopes. As the nuclei break down, rays or particles are given out. These are called emissions. |
| Quantum of energy | The smallest fixed amount of energy required for a change is called a quantum of energy. |
| First ionisation energy | The first ionisation energy, ΔHi1 , is the energy needed to remove one electron from each atom in one mole of atoms of an element in its gaseous state to form one mole of gaseous ions |
| molecular orbital | A covalent bond is formed when atomic orbitals (Section 1.4) overlap. Each orbital which combines contributes one unpaired electron to the bond. The ‘joined’ orbital is called a molecular orbital. |
| co-ordinate bond (dative covalent bond) | A co-ordinate bond (dative covalent bond) is formed when one atom provides both the electrons for the covalent bond |
| Electronegativity | Electronegativity is the ability of a particular atom involved in covalent bond formation to attract the bonding pair of electrons to itself. |
| Hydrogen bonding | is a special form of permanent dipole bonding. It requires: >one molecule with an H atom covalently bonded to an F, O or N atom. These are the most electronegative atoms >a second molecule having a F, O or N atom with a lone pair of electrons. |
| permanent dipole–dipole forces | Permanent dipole–dipole forces are the weak attractive forces between the δ+ of the dipole of one molecule and the δ of the dipole of a neighbouring molecule |
| van der Waals forces | van der Waals forces of attraction are not permanent. All atoms and molecules, including noble gas atoms, have van der Waals forces. Weak forces of attraction between molecules caused by temporary dipole-induced dipoles. |
| VSEPR theory | (VSEPR theory) can be used to work out the shapes of molecules. It uses the following rules: > Pairs of electrons in the outer shells of the atoms in a molecule repel each other and move as far apart as possible. This minimises repulsive forces in the mo |
| hybridisation. | This process of mixing atomic orbitals is called hybridisation |
| Molar mass | The molar mass, M, is the mass of one mole of specifed substance in grams |
| Relative atomic mass | >The average mass of one atom of an element compared with 1/12 the mass a carbon-12 atom >Relative atomic mass (Ar) is the weighted average mass of naturally occurring atoms of an element on a scale where an atom of 12C has a mass of exactly 12 units |
| Mole | >The relative atomic mass or relative molecular mass of a substance in grams is called a mole of that substance > The mole id the amount of substance that contains the same number of particles as there are atoms in 12grams of carbon-12 |
| redox reaction | Redox reactions are reactions where oxidation and reduction are both taking place at the same time. |
| Oxidation | A simple definition of oxidation is the gain of oxygen, loss of electrons and hydrogen |
| Reduction | A simple definition of reduction is the loss of oxygen, gain of electrons and hydrogen |
| Boyle's law states that..... what is the formula? | The law states that for a fixed (mass) number of moles of gas held at a constant temperature, the volume of a gas is inversely proportional to its pressure. P1 * P2 = P2 * V2 Initial pressure * initial volume = final pressure * final volume |
| Charles law states that .... What is the formula? | For a fixed number of moles of a gas at constant pressure, the volume of gas is directly proportional to its absolute (kelvin) V1/T1 =V2/T2 Initial vol/ initial temp(k) = final vol/final temp (k) |
| What is the combined gas law formula? | P1 * V2 / T1 = P2 * V2 / T2 |
| The kinetic theory of gases states that: | > Gas particles are moving randomly. > Gas particles do not attract each other. > Gas particles have no volume. > Collisions between gas particles are elastic, i.e. no energy is lost when they collide. |
| A gas which has the characteristics of the kinetic theory is called an ? | Ideal gas |
| Ideal gases obey which laws? | Boyles law and Charles law |
| What is the difference between Ideal gas and Real gas as it relates to pressure, temperature and the laws they obey? | IDEAL GAS REAL GAS > low pressure > High pressure >High temp > low temp >Obey charles and boyles law |
| What is the ideal gas equation? | PV = nRT OR PV = mRT/M |
| endothermic reaction | An endothermic reaction absorbs energy from the surroundings . The surroundings decrease in temperature. |
| exothermic reaction | An exothermic reaction releases energy to the surroundings. The surroundings increase in temperature. |
| Bond energy | Bond energy is the amount of energy needed to break one mole of a particular bond in one mole of gaseous molecules. This is also called bond dissociation energy. |
| Solubility | Solubility is the mass of solute which dissolve in a 100g of water to form a saturated solution at a specific temperature or pressure |
| Standard enthalpy change of reaction: | The enthalpy change when the amounts of reactants shown in the equation react to give products under standard conditions. Symbol ΔHrØ |
| Standard enthalpy change of neutralisation: | The enthalpy change when 1 mole of water is made in the reaction between an acid and an alkali under standard conditions. Symbol ΔHnØ |
| Standard enthalpy change of solution: | The enthalpy change when 1 mole of a substance is dissolved in a very large amount of water (to innite dilution) under standard conditions. Symbol ΔHØsol |
| Standard enthalpy change of combustion: | The enthalpy change when 1 mole of a substance is burnt in excess oxygen under standard conditions. Symbol ΔHcØ |
| Standard enthalpy change of formation: | The enthalpy change when 1 mole of a compound is formed from its elements under standard conditions. Symbol ΔHfØ |
| Standard enthalpy change of hydration: | The enthalpy change when 1 mole of a specied gaseous ion dissolves in enough water to form an innitely dilute solution under standard conditions. Symbol Δ HØ hyd |
| Lattice energy: | The enthalpy change when 1 mole of an ionic compound is formed from its gaseous ions under standard conditions. Symbol ΔHØ latt |
| Standard enthalpy change of atomisation: | The enthalpy change when 1 mole of gaseous atoms is formed from an element in its standard state under standard conditions. Symbol ΔHatØ |
| Electron affinity: | The frst electron affinity is the enthalpy change when 1 mole of electrons are added to a mole of gaseous atoms to form 1 mole of gaseous ions X . Symbol ΔHØ ea1 |
| What is Ionization Enthalpy | The enthalpy change associated with the removal of the first electron from an isolated gaseous atom in its ground state is called first ionization enthalpy. |
| transition element | A transition element is a d block element which forms one or more stable ions with an incomplete d electron sub-shell. |
| Why Scandium, Sc, and zinc, Zn, are not transition elements although they are d block elements? | Sc forms only one ion, Sc3+ , with no electrons in its d sub-shell. Zn forms only one ion, Zn 2+, and has a complete 3d sub-shell. |
| why the electronic configurations of Cr and Cu do not follow the expected pattern of filling the d sub-shell? | For Cr, the arrangement of a d sub-shell with one electron in each orbital, [Ar]3d5 4s1 , gives a greater stability than having one of the d orbitals completely lled. For Cu, the arrangement of a d sub-shell with paired electrons in each orbital, [Ar]3d |
| Characteristics of transition elements | >form compounds with different oxidation states. > form coloured compounds. >form complex ions. > Transition elements and their compounds are often good catalysts > have very high density. >have very high melting points and boiling points. > They ha |
| Most compounds and ions of the transition elements are paramagnetic what does this mean? | when placed in a magnetic field, they align themselves with the field. But they do not retain their magnetism when the magnetic field is removed. |
| Fe, Co and Ni are ferromagnetic what does this mean? | They retain permanent magnetism after the magnetic field has been withdrawn |
| Ligands | A ligand is a molecule or ion with one or more lone pairs of electrons available to donate to a transition element ion. Examples of simple ligands are water, ammonia and chloride ions |
| electrode potential | The measured difference between one metal–metal ion system and another system. |
| Standard electrode potential of a half-cell | The standard electrode potential, EØ, of a half cell is the voltage the half cell under standard conditions compared with a standard hydrogen electrode |
| standard cell potential | The standard cell potential is the voltage developed under standard conditions when two standard half cells are joined. |
| Hess’s law | The enthalpy change for a reaction is independent of the route by which the reaction takes place. |
| Ligand exchange | The replacement of one ligand by another in a transition element complex. |
| Brønsted–Lowry theory | An acid is a proton donor. A base is a proton acceptor. |
| Buffer solution | A solution that minimizes changes in pH when acids or alkalis are added to the solution. |
| Disproportionation | A redox reaction in which the same type of atom in a species is oxidized and reduced simultaneously |
| d-orbital splitting | The splitting of d-orbitals into a higher and lower energy level, caused by the presence of ligands around a central transition element ion |
| Ferromagnetic | A substance which, when placed in a magnetic field, lines itself up with the field and retains its magnetism when the magnetic field is removed. |
| Paramagnetic | A substance which, when placed in a magnetic field, lines itself up with the field but does not retain its magnetism when the magnetic field is removed |
| Le Chatelier’s principle | When the conditions affecting the position of equilibrium are changed, the position of equilibrium shifts to minimize the change. |
| Salt bridge | An inert support soaked in KNO3 used to make electrical contact between two half cells. |
| Standard hydrogen electrode | A half cell under standard conditions which has a Pt electrode dipping into 1moldm–3 H+ ions in equilibrium with H2 gas. |
| Strong acid/base | Acids or bases which are completely ionised in solution. |
| Transition elements | A d block element which forms stable ions with an incomplete d sub-shell. |
| Weak acid/base | Acids or bases which are partially ionised in solution |
| Redox reaction | A reaction where reduction and oxidation occur at the same time |
| Half-life | The time taken for the amount or concentration of a limiting reactant to decrease to half its initial value. |
Created by:
beyoncehutchinson
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