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powerpoint presentation notes on chapter 4 thermochemistry SPM
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Thermo chemistry Thermo chemistry The study of changes in heat The study of changes in heat
energy during chemical energy during chemical reactionreaction
ExothermiExothermic c
ReactionReaction
EndothermiEndothermic c
ReactionReaction
A chemical reaction that gives out or release of
heat energy to the surroundings
Exothermic ReactionExothermic Reaction
Chemical reaction that absorbs heat energy from
the surroundings
Endothermic Endothermic ReactionReaction
Energy Change During Energy Change During Formation And Breaking Of Formation And Breaking Of
Bonds Bonds Chemical Reaction :
bond breaking and bond formation
(absorb energy) (release energy)
If heat absorb to break the bonds higher than heat released during formation of bonds - endothermicendothermic
If heat absorb to break the bonds is lower than heat released during formation of bonds - exothermicexothermic
ENERGY LEVEL DIAGRAM ENERGY LEVEL DIAGRAM
Every chemical substances have certain amount of chemical
energy and different for different substances. Symbol is HHThe amount of heat energy released or
absorbed during chemical reaction heat of reaction.
Symbol is ΔΔHH, unit KJ mol KJ mol-1-1
ΔH = Total Energy Content Product – Total Energy Content Reactant
= Hproducts - Hreactants
The Energy Level Diagram For
Exothermic Reaction Endothermic Reaction
Reactants
Energy
Products
ΔH = - xKJmol-1
Reactants
Energy Product
s
ΔH = +yKJmol-1
APPLICATIONAPPLICATION
Separate compartment (thin film) of water + solid ammonium nitrate placed in a plastic bag
Squeezed it, the compartment broken and solid ammonium nitrate dissolved in water
Endothermic, provide instant coldness
Cold Pack
Separate compartment (thin film) of water + anhydrous calcium chloride placed in a plastic bag
Squeezed it, the compartment broken and anhydrous calcium chloride dissolved in water
Exothermic, release heat
Hot Pack
4 type of heat of 4 type of heat of reactions :reactions :
Heat of PrecipitationHeat of
NeutralizationHeat of DisplacementHeat of Combustion
HEAT OF PRECIPITATIONHEAT OF PRECIPITATION
m1
m2
DEFINATION :Heat of precipitation is the energy change
when 1 mole of precipitate is formedwhen 1 mole of precipitate is formed from its ions. To calculate Heat of PrecipitationStep 1 : find energy change , Q Q = mc m = m1 + m2 c = 4.2 = temp change
Step 2 : find mol, n both solution n = MV/1000
Step 3 : find H H = Q/ n KJ mol-1
-- - - - - - - -- - -
HEAT OF DISPLACEMENTHEAT OF DISPLACEMENT
DEFINATION :Heat of displacement is the energy change 1 1 mole of mole of
metal is displaced from its salt solutionmetal is displaced from its salt solution by more by more electropositive metalelectropositive metal
m
Excess metalTo calculate Heat of Displacement
Step 1 : find energy change , Q Q = mc m = m c = 4.2 = temp change
Step 2 : find mol, n solution n = MV/1000
Step 3 : find H H = Q/ n KJ mol-1
-- - - - - - - -- - -
HEAT OF NEUTRALISATIONHEAT OF NEUTRALISATIONDEFINATION :
Heat of neutralization is the energy change when 1 1 mole of watermole of water is formed from the neutralization between 1 mole of H+ ion from an acid and 1 1 mole of H+ ion from an acid and 1
mole of OH- ion from an alkali mole of OH- ion from an alkali
acidm1
Alkalim2
To calculate Heat of NeutralizationStep 1 :Step 1 : find energy change , Q Q = mc m = m1 + m2 c = 4.2 = temp change
Step 2 :Step 2 : find mol, n both solution n = mv/1000
Step 3 :Step 3 : find H H = Q/ n KJ mol-1
HEAT OF COMBUSTIONHEAT OF COMBUSTIONDEFINATION :
Heat of combustion is the heat given off when 1 1 mole of alcohol is burnt completelymole of alcohol is burnt completely in an excess
of O2 gas.
To calculate Heat of CombustionStep 1 : find energy change , Q Q = mc m = VOLUME OF WATER USED c = 4.2 = temp change
Step 2 : find mol, n (FOR FUEL/ ALCOHOL) n = Mass Of Alcohol Used Molar mass of AlcoholStep 3 : find H H = Q/ n KJ mol-1