CHEM Part3

7/29/2019 CHEM Part3

1/37

It involves the scientific study of the structure,

properties, composition, reactions, andpreparation (by synthesis or by other means) of

carbon-based compounds, hydrocarbons, and

their derivatives.

ORGANIC CHEMISTRY


2/37

an organic compound consisting entirely of

hydrogen and carbon.

HYDROCARBON

Sigma bond

A single bond

CxHx


3/37

Saturated hydrocarbons (alkanes or paraffins) are the

simplest of the hydrocarbon species and are composed

entirely of single bonds and are saturated with

hydrogen.

Unsaturated hydrocarbons have one or more double or

triple bonds (pi bond) between carbon atoms. Alkenes (olefins) has a double bond

Alkyne has a triple bond


4/37

Naming of Hydrocarbon

CnH2n+2 CnH2n CnH2n-2

n ALKANE ALKENE ALKYNE

1 METHane _______ _______

2 ETHane ETHene ETHyne

3 PROPane PROPene PROPyne

4 BUTane BUTene BUTyne

5, 6 so on PENTane,

HEXane so on

PENTene,

HEXene so on

PENTyne,

HEXyne so on


5/37

Introduction to Thermodynamics

Thermodynamics

is the scientific study of the interconversion ofheat and other kinds of energy.


6/37

The Nature of Energy

Energy

-is usually defined as the capacity to do work.


7/37

The Nature of Energy

Work

-directed energy change resulting from a process.


8/37

Types of Energy

Radiant energy

comes from the sun and isearths primary energy source.


9/37

Chemical Energy

Thermal energy

is the energy associated with therandom motion of atoms and molecules.


10/37

Types of Energy

Chemical Energy

is stored within the structuralunits of chemical substances.


11/37

Types of Energy

Potential Energy

is energy available by virtue of anobjects position.


12/37

Types of Energy

Kinetic Energy

the energy produced by amoving object.


13/37

Law of Conservation of Energy

Energy can neither be created nor destroyed butit can be transformed from one form to another.

the total quantity of energy in the universe isassumed constant.


14/37

Energy Changes in Chemical Reactions

Heat

is the transfer of thermal energy between twobodies that are at different temperatures


15/37


Surroundings

are the rest of the universe outside the system.


16/37


Systems

usually include substance involved in chemicaland physical changes.


17/37

3 types of systems

Open system

Closed system

Isolated system


18/37

Open system

can exchange mass and energy, usually in the form of heat withits surroundings.

Isolated system

does not allow the transfer of either mass or energy.

Closed system

allows the transfer of energy (heat) but not mass.


19/37

Exothermic process

any process that gives off heat-that is, transfers

thermal energy to the surroundings.

Endothermic process

in which heat has to be supplied to the system.


20/37

Change of Internal Energy

E=Ef-Ei

Ef-internal energies of the system in thefinalstates respectively.

Ei-internal energies of the system in theinitialstates respectively.


21/37

The internal energy of a system has two

components:

Kinetic energy

Potential Energy


22/37

Work and Heat

Work

done by the gas on the surroundings.

W=-P


23/37

Work

V= the change in volume is given byVf-Vi

1L.atm = 101.3 J


24/37

Enthalpy of Chemical Reactions

Enthalpy

H=E+PV

H=enthalpy

E=is a internal energy of the systemP=pressure of the system

V=volume of the system


25/37


Enthalpy of Reactions

The difference between the enthalpies of theproducts and the enthalpies of the reactants.


26/37


Thermochemical Equations

H=6.01 kJ/mol

The per mole in the unit forHmeans that thisisthe enthalpy change per mole of the reaction

(or process) as it is written.


27/37


A Comparison ofHandE

E=H-PV

E=H-RTn

n=number of moles of product gases-number ofmoles of reactant gases


28/37

Standard Enthalpy of Formation and

Reaction

Standard Enthalpy of Formation (Hf)

the sea level reference point for all enthalpyexpressions.


29/37

Standard Enthalpy of Formation and

Reaction

Standard Enthalpy of Reaction(H rxn)

The enthalpy of a reaction carried out at 1 atm.


30/37

Calorimetry

The measurement of heat changes.

Calorimeter-a device that measured the

heat changes in physical andchemical processes.


31/37

Constant-Volume

refers to the volume of the container whichdoest not change during the reaction.


32/37

Calorimetry

Constant-Volume Calorimetry

heat of combustion is usually measured byplacing a known mass of a compound in asteel container.


33/37

Calorimetry

Constant-Pressure Calorimetry

which is used to determine the heat changes fornoncombustion reactions.

1 cal=4.184J


34/37

THERMOCHEMISTRY

is the study of heatchange in chemical

reactions.


35/37

Heat

heat is not a state function.


36/37

Specific Heat and Heat Capacity

Specific heat(s)-is the amount of heat required

to raise the temperature of 1 gram pf thesubstance by 1 degree Celsius.

Heat Capacity (C)- is the amount of heat

required to raise the temperature of a given

quantity of the substance by 1 degree Celsius.


37/37

Heat Capacity

C=ms

CHEM Part3

Documents

Transcript of CHEM Part3