PREPARED BY:
NOR SYAFINAZ BINTI ABDUL GHANI
MIC2A2
2010466248
THERMOCHEMISTRY
 Thermal
energy is the energy associated with
the random motion of atoms and molecules.
 Heat is the transfer of thermal energy
between two bodies that are different
temperature.
 Temperature is a measure of thermal energy.
Enthalpy of a system is the heat content of the system or
the sum of the internal energy and the product of its
pressure & volume.
Also known as heat content.
Enthalpy (H) is used to quantify the heat flow into and
out of a system in a process that occurs at constant
pressure
∆H˚=∑ H˚ᶠ(products)-∑H˚ᶠ(reactants)
∆H : heat given off or absorbed during a reaction at
constant pressure.
exothermi
c
Internal energy
of reactant is
greater than the
product
endothermic
Internal energy
of product is
greater than the
reactant
Heat released to
the surrounding
Heat is absorbed
from the
surrounding
∆H is negative
∆H is positive
∆H<0
∆H>0
2H2(g) + O2(g)
energy
heat
2H2O(l)
2Hg (l) + O2(g)
Energy
heat
2HgO(s)
The enthalpy of combustion
•Energy released as heat when a compound undergoes complete combustion with
oxygen under stated condition of temperature & pressure.
The enthalpy of neutralisation
•Heat released when one mole water is formed when an acid reacts with a base under
stated condition or during the neutralisation of strong acid by an alkali.
•The value is always negative
The enthalpy of solution
•The heat change when one mole of substance or a certain amount of solute dissolve
in a certain amount of solvent.
The enthalpy of formation
•The heat change when one mole of a compound is formed from its element s at
stated temperature and pressure.
The enthalpy of reaction
•The enthalpy change in reaction when both reactantas and products are at their
standard states at 298 K.
Calorimetry
•Measurement of heat flow.
Calorimeter
•Apparatus that measures
heat flow.
Molar heat capacity
•Heat capacity of 1 mol of a
substance.
Heat capacity
•The amount of energy
required to raise the
temperature of an object.
Specific heat capacity
•Heat capacity of 1g of a
substance.
For any chemical change made in several
steps, the net ∆H is equal to the sum of the
∆H
values of the separate steps
Balance the
equation(s).
complete balancing
– all levels must have
same atoms
Add axes and ∆H
values.
Sketch a rough draft
based on ∆H values.
Draw the overall
chemical reaction as
an enthalpy diagram.
Check arrows.
Draw a reaction
representing the
intermediate step.


Enthalpy cycle used to calculate lattice
enthalpy of an ionic compound
Two different routes to form an ionic
compound.


The enthalpy change when one mole of an
ionic solid is formed from its gaseous ions.
The values are always negative because of
formation of ionic bond.
CHEMICAL KINETICS

The change in the concentration of a reactant
or a product with time (M/s)
A
B
reactant(-)
product(+)
rate of appearance
= positive
rate of dissapearance = negative


Expresses the relationship of the rate of
reaction to the rate constant and the
concentrations of reactants raised to some
powers.
aA+bB→ cC+dD
Rate = k [A]x [B]y
Order of reaction
xth order in A
yth order in B
(x+y)th is the overall order
ORDER
RATE LAW
CONCENTRATI
ON- TIME
EQUATION
HALF-LIFE
0
Rate=k
[A]= [A]- kt
.t1/2=[A]/2k
1
Rate=k[A]
Ln[A]= ln[A]-kt t1/2= ln2/k
2
rate=k[A]^2
1/[A]=1/[A]
+kt
t1/2= 1/k[A]




Concentration of reactants – concentration of
reactants increase, so does the likehood that
reactant molecules will collide.
Temperature – at high temperature,reactants
molecules have more kinetic energy,move
faster and collide more often.
Catalyst – speed rxn by changing mechanism.
Activation energy – minimum amount of
energy required for reaction.
k=
(-Ea/RT)
A.e
Ea = activation energy (J/mol)
R = gas constant (8.314 J/K.mol)
T = absolute temperature
A = frequency factor

At two temperature, T1 and T2
Ln k1/k2=Ea/R(1/T2-1/T1)


The overall progress of a chemical reaction
represented by a series of elementary steps.
The sequence of elementary steps lead to
product formation is the reaction mechanism.
Molecularity
Unimolecular
Elementary reaction
A
product
Rate law
Rate = k[A]
Bimolecular
A+A
product
Rate = k[A]2
Bimolecular
A+B
product
Rate = k[A][B]
Termolecular
A + A +A
product
Rate = k[A]3
Termolecular
A+A+B
product Rate = k[A]2[B]
Termolecular
A+B+C
product
Rate = k[A][B][C]
CHEMICAL EQUILIBRIUM
Homogenous
equilibrium
Heterogenous
equilibrium
•Reacting species are the same phase
•i.e: N2O2(g)
2NO2(g)
•K’c = [ NO2 ]2 / [ N2O2 ]
•Reactants and product are in different phases
•i.e: CaCo3 (s)
CaO (s) + CO2 (g)
•K’c = [CaO] /[CaCo3]
•The concentration of solid and pure liquid are not
included in the expression for the equilibrium contant.
K p = Kc
∆n
(RT)
R = room pressure = 0.0821
∆n = moles of gaseous productsmoles og gaseous reactant

If an external stress is applied to a system at
equilibrium,the system adjusts in such a way
that the stress is partially offset as the system
reaches a new equilibrium position
change
Shift equilibrium
Change equilibrium
constant
Concentration
yes
no
Pressure
Yes
no
Volume
Yes
no
Temperature
Yes
yes
catalyst
No
no
IONIC EQUILIBRIUM
ᾱ = [H3O] / [acid]
ᾱ = [H3O] / [acid] x 100
1.For strong acid
pH=-log [H]
2.For weak acid
[H]=√KaC
[OH]=√KbC
3.pH of Buffer
pH= pKa-log[acid/salt]
pOH=pKa-log[base/salt]
pKa= -logKa
4. Kw = [H][OH] = Ka x Kb = 1 x 10-4
PHASE EQUILIBRIUM



A homogeneous system
Separated from other parts of system by
a dinstinct boundary
3 phase of state
solid
liquid
gaseous


No boundary between subtances –
hemogenous
i.e:
g-g system : oxygen and
nitrogen
l-l system : water and
ethanol
s-s system :
gemstone


Two substance with a boundary separating
them
i.e: l-l : water and oil
l-g : water and water vapour
s-g : ice and water vapour
s-l : ice and water


3 substance with boundaries separating each
other
i.e: s-l-g : ice, water and water vapour
system

The least number of independently
variable constituents which must be
specified so that composition of each
and every phase is described.

The smallest number of independent
variables of components (temperature,
pressure, concentration) which must be
specified to define completely the remaining
variables of the system
F=C–P+2
More components, more degree of freedom
More phases involved, less degree of freedom
Water and carbon dioxide
pressure, atm
solid
liquid
0.006
gas
0.01
temperature,(0c)
pressure, atm
liquid
solid
5.1
gas
-57
temperature, (0c)
Two completely immisible
solids (l-s)


Eutectic mixture – a mixture of 2 or
more subtance with melting point lower
than any other mixture of the same
subtance
Eutectic system – a mixture of chemical
compounds or elements that has a
single chemical composition that
solidifies at a lower temperature than
any other temperature
Deviation from raoult’s law
Negative deviation
Positive deviation
•Vapour-composition
diagram of solution
have minimum point
•Vapour-composition
diagram of solution
have maximum point
•Boiling-composition
diagram has
maximum point
•Boiling-composition
diagram has
minimum point

Partition coefficient= the ratio between the
concentration of the
solute in the two
solvents is,
experimentally
constant.
Kc= [solute in upper layer]/[solute in
the lower layer]
Kc=
X/volume of ether
mass of substance-X/volume of
water