Thermodynamics 0.0 / 5 ? ChemistryEntropyEnthalpyA2/A-levelAQA Created by: champion1607Created on: 26-05-18 14:06 Define lattice formation enthalpy 1 mole of solid ionic compound s formed from its gaseous ions 1 of 23 Define lattice dissociation enthalpy 1 mole of a solid ionic compound is completely dissociated into its gaseous ions 2 of 23 Define enthalpy change of atomisation of an element 1 mole of gaseous atoms is formed from an element in its standard states 3 of 23 Define first ionisation energy 1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms 4 of 23 Define first electron affinity 1 mole of gaseous 1- ions is made from 1 mole of gaseous atoms 5 of 23 Define enthalpy change of hydration 1 mole of aqueous ions is formed from gaseous ions 6 of 23 Define enthalpy change of solution 1 mole of an ionic substance dissolves in enough solvent to form an infinitely dilute solution (there is no change in concentration) 7 of 23 What useful acronym can be used to remember the order of Born-Haber cycles? FAIEL 8 of 23 What does the purely ionic model assume? Assumes that all ions are spherical, and have their charge evenly distributed 9 of 23 Why us experimental lattice enthalpy data different from actual data? Because most ionic compounds have covalent character and aren't wholly spherical 10 of 23 What is entropy? Entropy tells you how much disorder there is, represented by S 11 of 23 Which state has the lowest entropy and which has the highest? Solids have the lowest and gases have the highest 12 of 23 Dissolving a solid does what to the entropy? Increases the entropy 13 of 23 How do you calculate entropy change? S= S products -S reactants 14 of 23 What is free energy change ? A measure used to predict whether a reaction is feasible and carry on to completion without any energy being supplied to it 15 of 23 When is a reaction feasible? When G is negative or equal to zero 16 of 23 How do you calculate free energy change (G) ? G = H - TxS 17 of 23 If a reaction is exothermic and has a positive enthalpy... ...G is always negative and feasible at any temperature 18 of 23 If a reaction is endothermic and has a negative entropy change... ...G is always positive and reactions are not feasible 19 of 23 If H is positive and S is positive.... ....the reaction will only be feasible above a certain temperature 20 of 23 If H is negative and S is negative... ...the reaction will only be feasible below a certain temperature 21 of 23 How do work out the temperature when a reaction is feasible? T = H/S 22 of 23 So on a graph where G is the y-axis and T is the x-axis... ...the gradient of the line is equal to -S and the y-intercept is equal to H 23 of 23
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