Basic Introduction of Chemical Reaction

1. CHEMICAL REACTIONS
for Class DAE 1st Year Chemical Technology
MUHAMMAD SHAKAIB QURESHI
M.PHIL CHEMISTRY

2. CONTENT
• INTRODUCTION
• COLLISION THEORY OF MOLECULE
• TYPES OF CHEMICAL REACTIONS

3. Introduction
• Chemical reaction, a process in which
one or more substances, the reactants,
are converted to one or more different
substances, the products. Substances
are either chemical
Element or Compound.
• Reactants are in left Hand Side Which
Reacts together and formed products
which are in right hand Side.

4. Combustion Reaction

5. How Chemical Reaction Happens ?
Collision Theory of Molecules
Postulates
• In order for a chemical reaction to take place, the reactants
must collide. The collision between the molecules in a chemical
reaction provides the kinetic energy needed to break the
necessary bonds so that new bonds can be formed.
• Sometimes, even if there is a collision, not enough kinetic
energy is available to be transferred — the molecules aren’t
moving fast enough. You can help the situation somewhat by
heating the mixture of reactants. The temperature is a
measure of the average kinetic energy of the molecules;
raising the temperature increases the kinetic energy available
to break bonds during collisions.

6. Continue
• Sometimes, even if there is a collision, not enough
kinetic energy is available to be transferred — the
molecules aren’t moving fast enough. You can help
the situation somewhat by heating the mixture of
reactants. The temperature is a measure of the
average kinetic energy of the molecules; raising the
temperature increases the kinetic energy available to
break bonds during collisions.

7. • The molecules must also collide in the right orientation, or hit at the right
spot, in order for the reaction to occur.
• Here’s an example: Suppose you have an equation showing molecule A-B
reacting with C to form C-A and B, like this:
• A-B + C→C-A + B
• The way this equation is written, the reaction requires that reactant C
collide with A-B on the A end of the molecule. If it hits the B end, nothing
will happen. The A end of this hypothetical molecule is called the reactive
site, the place on the molecule that the collision must take place in order
for the reaction to occur.
• If C collides at the A end of the molecule, then there’s a chance that
enough energy can be transferred to break the A-B bond. After the A-B
bond is broken, the C-A bond can be formed. The equation for this reaction
process can be shown in this way:
• C~A~B→C-A + B
• So in order for this reaction to occur, there must be a collision between C
and A-B at the reactive site. The collision between C and A-B has to transfer
enough energy to break the A-B bond, allowing the C-A bond to form.

8. Energy is required to break a
bond between atoms.
ACTIVATION ENERGY

10. Factors Affecting on Chemical
Reaction
• Nature of Reactant
• Catalyst
• Concentration
• Temperature
• Pressure

12. Example
Catalyzed Reaction

13. Types of Chemical Reactions
• Addition/Synthesis Reactions:
• Addition reactions, also known as synthesis reactions or
direct combination reactions, involve two or more
reactants combining to form a single, more complex
product. Examples are the reaction of iron and sulfur to
form iron sulfide, or, in organic chemistry, the reaction of
ethene and bromine to form dibromoethane.
• Example: C2H4 + Br2 → C2H4Br2

14. • Decomposition Reactions:
• A decomposition reaction involves the breaking down of a
chemical compound into elements or simpler compounds. It
is sometimes defined as the opposite of a synthesis
reaction. They can occur spontaneously, or be initiated by
heat, a catalyst, or electrolysis. An example is the
decomposition of hydrogen peroxide into hydrogen and
oxygen.
• Example: 2H2O2 → 2H2O + O2

15. • Combustion Reactions:
• Combustion reactions involve oxygen reacting with another
element or compound to produce energy in the form of
heat & light. They are always exothermic. Complete
combustion requires a plentiful supply of oxygen – in a
limited supply, incomplete combustion occurs, and
different products can be formed. When organic chemicals
combust completely, the products always include carbon
dioxide and water.
• Example: CH4 + 2O2 → 2H2O + CO2

16. • Neutralization Reactions:
• A neutralization reaction is one in which an acid and a base
react to form a salt. Water is commonly produced as well.
Often these reactions are exothermic, but endothermic
neutralizations are possible. Neutralization reactions do not
necessarily result in a pH of 7 – resultant pH is dependent
on the strength of the acid and the base.
• Example: NaOH + HCl → NaCl + H2O

17. • Precipitation Reactions:
• A precipitation reaction is one in which aqueous
compounds react to form an insoluble solid, called a
precipitate. This solid can be suspended throughout the
solution, or fall to the bottom of the reaction vessel.
Whether or not the product of a reaction will form a
precipitate is determined by solubility rules for ionic
compounds.
• Example: 2NaOH(aq) +MgCl2(aq) → 2NaCl(aq) + Mg(OH)2(s)

18. • METATHESIS OR DOUBLE DISPLACEMENT REACTION
• In a double displacement or metathesis reaction two
compounds exchange bonds or ions in order to
form Different Compounds.
AB + CD → AD + CB
An example of a double displacement
reaction occurs between sodium chlorideand silver nitrate
to form sodium nitrate and silver chloride.
NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s)

19. • SUMMARY

20. THE END