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THERMOCHEMISTRY - Coggle Diagram
THERMOCHEMISTRY
Concept of Enthalpy
Types of system**
•Open system-exchange mass and energy with its surroundings
•closed system-allows the exchange of energy with surroundings
•Isolated system-does not allow the exchange of either mass or energy with surrounding
Types of reactions
Endothermic reactions
•absorbs energy from surroundings to system •increase the result in the enthalpy of a system •Enthalpy(H) of the product is greater than the enthalpy of reactant(H product>H reactants)
•deltaH: (+ value)
Exothermic reactions
•release energy from system to surroundings
•decrease the result in the enthalpy of a system
•Enthalpy the reactants is greater than the enthalpy of the product (H reactatant>H product)
•deltaH:(-value)
Enthalpy change,deltaH deltaH: Hproducts-HreactantsStandard Enthalpy, deltaH •standard state: 1 atm,298K, 25 celsius
Type of Enthalpy changes
Enthalpy of formation, deltaHf
Heat change when 1 mole of a compound its formed from its elements in their most stables state at standard conditions(1 atm, 298K) Enthalpy of formation of water
Enthalpy of combustion, deltaHc Heat released when 1 mole of substance completely combusted in oxygen gas
Enthalpy of Atomization,deltaHatom The heat absorbed when 1 mole of gaseous atoms is formed from its elements
Enthalpy of Neutralization,deltaHneut Heat released when 1 mol of water is formed when acid reacts with base
Enthalpy of Hydration deltaHhyd Heat released when 1 mole of gaseous ion is hydrated in aqueous solution
Enthalpy of solution,deltaHsoln Heat change when 1 mol of substances dissolve in solvent(water) to form an infinite dilute solution
Calorimetry- the measurement of heat flow Calorimeter- to measure the heat released or absorb by physical or chemical process
• constant volume calorimeter Bomb calorimeter- measure heat of combustion
• constant pressure calorimeter simple calorimeter -heat of neutralizaton -heat of solution
•Hea released by reaction: heat absorbed by water and calorimetry
Heat capacity(c) of substance amount of heat(q) required to raise remperature of given quantity of substance by 1K or 1C qreleased+qabsorbed=0
Hess' law
• when reactants are converted to product, the change in enthalpy is the same when the reaction take place in the series of steps
•method to calculate deltaH,
-algebraic method -energy cycle method
Dissolution Process of Ionic Solids
•When an ionic compound dissolves in water,
there is an enthalpy change.
Breaking the Crystal Lattice
•Na+ and Clions in the solid crystal are separated from
each other and converted to the gaseous state (deltaHlattice) •This process requires energy (endothermic) to
overcome the electrostatic forces between ions.
Hydration process
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Born-Haber-Cycle
Lattice energ
•energy released when 1 mol of solid ionic compund formed from its gaseous ions Magnitude of Lattice energy
•ionic charges increase
•ionic size decrease
Ionic charges increase(more negative/exothermic)
•electrostatic force of attraction between ions increase
Ionic size decrease(more negative/exothermic)
•ions get closer to each other increasing the strength of the attractions