Enthalpy changes

easy notes on enthalpy changes,,really helpful for almost all boards...

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  • Created on: 05-05-13 17:56
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Enthalpy Changes:
An Enthalpy Change is the heat energy exchange with surroundings at constant pressure
Energy Pathway Diagrams.
Exothermic
= POSITIVE
This diagram represents an exothermic reaction.
During an exothermic reaction, heat energy is released to the surroundings. An energy loss from the chemicals is
balanced by the same energy gain to the surroundings, which rise in temperature.
In an Exothermic reaction, is negative.
Heat Is given out ( to the surroundings)
The reacting chemicals lose energy
Endothermic:
During an endothermic reaction, heat energy is taken in from the surroundings.

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Any energy gain to the chemicals provided by the same energy loss from surroundings, which fall in temperature.…read more

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H2(g) + ½ O2(g) => H20(l)
NOTE: for an element, the standard enthalpy change of formation is defined as Zero
Standard Enthalpy Change of Neutralisation
The standard enthalpy change of neutralisation is the energy change when an acid and base form 1 mole of water
under standard conditions of 298k and 1 atmosphere pressure
HCl(aq) +NaOH(aq) => NaCl(aq) + H20(l)
acid base 1 mol…read more

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