Chemistry UNIT 5 Enthalpy & Entropy 0.0 / 5 ? ChemistryEnthalpyEntropyA2/A-levelAQA Created by: JessAnnBCreated on: 31-03-16 15:01 What is the enthalpy of formation? Enthalpy change when one mole of a substance is formed from its elements in their standard states under standard conditions. 1 of 24 What is the first ionisation enthalpy? The energy required to remove one electron from one mole of gaseous atoms to produce 1 mole of gaseous ions each with a charge of 1+. 2 of 24 What is enthalpy of atomisation of an element? The enthalpy change when one mole of free gaseous atoms is produced from that element in its standard state. 3 of 24 What is first electron affinity? The energy released when 1 mole of gaseous atoms each acquire an electron to form 1 mole of gaseous 1- ions. 4 of 24 What is bond dissociation enthalpy? The mean enthalpy change when one mole of covalent bonds is broken homolytically, resulting in free gaseous atoms. 5 of 24 What is Lattice enthalpy? The enthalpy change when one mole of an ionic compound is formed from its free gaseous ions. 6 of 24 What is Lattice dissociation enthalpy? The enthalpy change when one mole of an ionic compound is completely dissociated into free gaseous ions. 7 of 24 What is the enthalpy of hydration? The enthalpy change when one mole of free gaseous ions is added to an excess of water. 8 of 24 What is enthalpy of solution? The enthalpy change when one mole of an ionic compound is completely dissolved in an excess of water. 9 of 24 What is entropy (ΔS)? A measure of the disorder in a substance. 10 of 24 What does the perfect ionic model of a lattice assume? That all the ions are spherical and have their charge evenly distributed around them. 11 of 24 What does it show if the experimental and theoretical lattice enthalpies for a compound are very similar? It shows that the compound has very little covalent character. 12 of 24 When will distortion most likely happen? 1.When there is high charge density on the cation(+ve), 2.When there is a large or high charge anion(-ve). 13 of 24 What can cause a high charge density on the cation? Very small cation, high charge on cation. 14 of 24 What is a special case of a very small cation? Ag+. 15 of 24 What is the equation that links lattice dissociation enthalpy, Hydration enthalpy and enthalpy of solution? Solution = Dissociation + Hydration. 16 of 24 What is a spontaneous reaction? Reactions that will occur on their own accord without the input of energy from the surroundings. 17 of 24 Does a solid have high or low entropy? Low. 18 of 24 Is the entropy value of an element zero? No. 19 of 24 What could increase the entropy value? A reaction that increases the moles or results in the formation of gas. 20 of 24 What is free energy change (ΔG)? A measure used to predict whether a reaction is feasible? 21 of 24 What is the equation for free energy? ΔG = ΔH - TΔS 22 of 24 What could happen if ΔG is less than 0? The reaction might happen by itself. 23 of 24 What is the equation to work out ΔS of surroundings? -ΔH/T 24 of 24
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