Aqa A-Level Chemistry Paper 1 Study Guide Graded A+

Define the term Ligand {Ans: Atom, ion or molecule which can donate a pair of electrons to a metal ion}what happens when and ionic compound dissolves in water? {Ans: the ionic lattice breaks up (enthalpy of lattice dissociation ) the polar water molecules form bonds with the ions (enthalpy of hydration)}State Hess' law {Ans: Enthalpy change for any chemical reaction is independent of the route taken, and depends only on the initial and final states.}Why is the second electron affinity endothermic? {Ans: Repulsion of the negative ion with the negative electron being added}Define enthalpy of lattice formation {Ans: The enthalpy change when 1 mole of an ionic compound is formed from its component gaseous ions}Which Enthalpy Changes are Endothermic? {Ans: enthalpy of lattice dissociation enthalpy of atomisation 1st/2nd ionisation enthalpy 2nd electron affinity bond dissociation enthalpy}What does the sign of the enthalpy of solution depend on? {Ans: The balance between the lattice enthalpy (endothermic) and the enthalpy of hydration (exothermic)}Define mean bond enthalpy {Ans: the energy required to break one mole of covalent bond averaged over compounds containing that bond. (kJmol-1)}Define enthalpy of formation {Ans: Enthalpy change when 1 mole of