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Heat (q) is a form of energy- it has nomass, no volume or shape. It isdetected by how it affects matter.

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The energy stored in the structural units(bonds) of substance.

For example you get energy from the food youeat when the chemical bonds in the food arebroken and new bonds are formed.

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Heat flowing into a system (+q), absorbs heatfrom the surroundings. Endothermic processeshas a + value for q.

If you have to add heat to something in orderfor it to react you have an endothermic process.

If the potential energy of the products is

greater than the potential energy of thereactants, heat has been added(+q).

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A process that releasesheat to theenvironment. (-q)

Reactions that releaseheat

The potential energy of

the products is less thanthat of the reactants.

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Calorie- unit of heat or energy

1 Calorie= 1 kilocalories=1000 calories

1 Joule= 0.2390 cal

4.18 J= 1 calorie

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The amount of heat (energy) needed to raisethe temperature of an object by 1 degreeCelsius

Specific Heat Capacity- the amount of heatrequired to raise the temperature of 1g of thesubstance by 1 degree Celsius.

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Q=mc(T or q=mc(T

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For systems at constant pressure- Enthalpy (H)is the same as heat content

Exothermic reactions (H is negative

Endothermic reactions (H is positive

q= (H=mc(T

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Given the Reaction:

2 NaHCO3 (s) + 129 KJ Na2CO3 + H2O(g) +CO2(g)

How much heat would it take to decompose 2.24moles of baking soda?

(H= 2.24 moles NaHCO3 x 129KJ/2 moles

NaHCO3(H= 114 KJ

So is heat absorbed or released?

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The heat of reaction for the complete burningof one mole of a substance.

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The Phase diagramgives the conditionsof temperature and

pressure at which asubstance exists as aliquid, solid or gas.

Triple point- the

conditions at whichall three phases ofmatter can existtogether.

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The change in state from a solid directly into agas without passing through the liquid phase.

Examples- dry ice will sublime at room temperature.

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All solids absorb heat when they melt. Theamount of heat required to melt one mole of asubstance is the molar heat of fusion ((Hfus)

The amount of heat lost when one mole of aliquid becomes a solid is the molar heat ofsolidification ((Hsolid)

(

Hfus= -(

hsolid

Note- during a melting process there is notemperature change so no (T

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Heat of vaporization- the amount of heatnecessary to change one mole of a substance toa gas ((Hvap)

Heat of condensation- the amount of heatnecessary to change one mole of a substancefrom a gas to a liquid.((Hcond)

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(Hfus= 6.01 KJ/mol

(Hsolid= -6.01 KJ/mol

(Hcond= -40.7 KJ/mol

(Hvap= 40.7 KJ/mol

The high values for the heat of vaporization of

water explains why steam burns at 100oC aremore painful that water burns at 100oC.

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Heat change can also occur when a solutedissolves in a solvent ((Hsoln) Example- when sodium hydroxide dissolves in

water heat is given off ((H= -445.1KJ/mol)

NaOH (s) NaOH(aq) + 445.1 KJ

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Many reactions take place in multiple steps-and you can add the heats of reaction to get theheat for the final, net equation.

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The change of enthalpy that accompanies theformation of one mole of a substance.

(Hf= you look these up in a table

(,f= (Hf (products) (Hf( reactants)

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Compound (kJ/mol) Compound (kJ/mol)

AgBr(s) -99.5 C2H2(g) +226.7

AgCl(s) -127.0 C2H4(g) +52.3

AgI(s) -62.4 C2H6(g) -84.7

Ag2O(s) -30.6 C3H8(g) -103.8

Ag2S(s) -31.8 n-C

4H

10(g) -124.7

Al2O3(s) -1669.8 n-C5H12(l) -173.1

B Cl2(s) -860.1 C2H5OH(l) -277.6

B CO3(s) -1218.8 CoO(s) -239.3

B O(s) -558.1 Cr2O3(s) -1128.4

B SO4(s) -1465.2 CuO(s) -155.2

CaCl2(s) -795.0 Cu2O(s) -166.7

CaCO3 -1207.0 CuS(s) -48.5

CaO(s) -635.5 CuSO4(s) -769.9

Ca(OH)2(s) -986.6 Fe2O3(s) -822.2

CaSO4(s) -1432.7 Fe3O4(s) -1120.9

CCl4(l) -139.5 HBr(g) -36.2

CH4(g) -74.8 HCl(g) -92.3

fH( fH(Heat of Formation Table

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Pressure- for reactants that are gases increasingthe pressure will cause particles to collide moreoften- resulting in an increased rate of reaction

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The Law of disorder states that processes movein the direction of maximum disorder and ittakes work ( free energy) to reverse disorder.

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(So= So ( products)- So ( reactants)

These values can be found in a Standard Entropy table

The Heat change ((H) and the Entropy Change ((S) determine if areaction is spontaneous or not.

Heat Change Entropy Spontaneous

Decreases (exothermic) Increases ( more disorder inproducts than reactants

Yes

Increases (endothermic) Increases Only if unfavorable heat changeis offset by entropy

Decreases (exothermic) Decreases( less disorder inproducts)

Only if unfavorable entropy isoffset by enthalpy

Increases( endothermic) Decreases No

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(G= (H-T(S Temp must be in Kelvin

Gibbs Free Energy is the energy available to dowork. Can also be looked up in a table

(G= (G ( products) (G( reactants)

-(G means that the reaction is spontaneous, +(Gmeans that additional energy must be provided inorder for the reaction to procede.