35229942
Description
Flashcards by Leanne Tan, updated more than 1 year ago
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Created by Leanne Tan
almost 3 years ago
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| Question | Answer |
| define enthalpy change | the amount of heat energy taken in or given out during any change in the system, provided the pressure is constant |
| what is an exothermic reaction? | - energy is transferred from the system to the surroundings (usually releasing heat) - the overall enthalpy change is negative |
| what is an endothermic reaction? | - when (thermal) energy is absorbed from the surroundings into the system - the overall enthalpy change is positive |
| define the standard enthalpy change of formation | the enthalpy change when 1 mole of a compound is formed from its elements under standard temperature and pressure |
| what is standard pressure? | 100kPa (~1 atmosphere) |
| what is standard temperature? | 298 K, 24.85 Celcius |
| define the standard enthalpy change of combustion | the enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions |
| what is standard concentration? | 1 mol/dm3 |
| what does incomplete combustion produce? | - carbon particulates - water - carbon monoxide - will be less exothermic than complete combustion |
| define the standard enthalpy of electron affinity | the energy released when 1 mole of gaseous atoms each gains an electron to form 1 mole of gaseous 1- ions |
| define the standard enthalpy of neutralisation | the enthalpy change when acid and alkali react together under standard conditions to form 1 mole of water |
| define the standard enthalpy of atomisation | the heat energy needed to produce 1 mole of gaseous atoms from the element in its standard state |
| define the standard enthalpy change of ionisation energy | the energy required to remove the most loosely held electron from 1 mole of gaseous atoms to produce 1 mole of gaseous 1+ ions |
| define the standard enthalpy change of lattice enthalpy | the heat energy change when 1 mole of solid ionic lattice is formed from its scattered gaseous ions |
| are neutralisation reactions exothermic or endothermic? | always exothermic |
| state Hess' law | total enthalpy change for a reaction is independent of the route taken to get from reactants to products |
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