The document explains chemical reactions, which are processes where substances transform into new ones, described by chemical equations. It details the types of chemical reactions, how to balance equations, and provides guidelines for predicting products of reactions. Key elements include reactants, products, and the symbols used in equations to denote states of matter and reaction types.

1. Chemical
Reactions
and
Equations

2. CHEMICAL REACTIONS
are processes in which
substances change into other
substances

3. • Is the process by
which a chemical
change takes
place.
• A change where
a new substance
is formed.

4. The meeting of two
personalities is like the
contact of two chemical
substances: if there is any
reaction, both are
transformed.
Carl Jung

5. Chemical equations are the symbolic
representation of chemical reactions.
In symbols, chemical equations is written as:
reactants → products
Coefficient is a number before the symbol or
formula of a substance while subscript is the
number of atoms of the element found in the
substance

6. The chemical reactions has two major
parts, these are:
1. Reactants, and
2. Products
Reactants Products
The starting materials.
These are the substances
that change when it is
combined with another
substance in a chemical
reaction
The new substance/s
The substance/s as result
of the chemical reaction

7. Other symbols and its meaning used in
chemical equations are as follows:
Symbol Meaning:
+
Used to separate one reactant or product from one
another.Can be read as “reacts with” when used in reactant,
read as “and” when it is used in product.
→ Used to separate the reactants from the products read as
"yields" or "produces" in an equation.
(s) ↓ Indicates that the substance is in the solid state.
(l) Indicates that the substance is in the liquid state.
(g) ↑ Indicates that the substance is in the gas state.
(aq) Indicates that the substance is dissolved in water. It comes
from the term “aqueous”
Indicates that there is heat applied or needed to make the
reaction proceed.

9. A chemical reaction takes place if
one or more of these occur:
• Color changes- Different combinations of molecules reflect light
differently. A color change indicates a change in molecules.
• Heat content changes- In all chemical reactions, the heat content
of the reactants and the heat content of the products is neverthe
same. Sometimes the difference is great and can be easily detected.
At other times, the difference is slight and more difficult to detect.
• Gas produced- Whenever a gaseous product forms in a liquid
solution, bubbles can be seen. A colorless gas produced in a reaction
of solids is much harder to detect.
• Precipitate forms- Precipitates are insoluble products formed by
a reaction taking place in a liquid solution. This insoluble product
will eventually settle to the bottom, but might immediately appear
by turning the clear solution cloudy.

10. What is a Balanced
Chemical Equations?
A balanced chemical equation has equal
numbers of atoms for each element
involved in the reaction are represented
on the reactant and product sides. This
is a requirement the equation must
satisfy to be consistent with the Law of
Conservation of Matter.

11. Steps in Balancing
Chemical Equations:
1. Check for diatomic molecule. Diatomic
molecules composed of only two atoms, of
either the same or different chemical elements.
This includes H2, O2, N2, Cl2, Br2, F2 and I2.
2. Check whether the chemical formulas of all the
reactants and products are written correctly.
Check the total number of atoms of each
element on each side of the equation.

12. Steps in Balancing
Chemical Equations:
3. A polyatomic ion appearing unchanged on
both sides of the equation is counted as a
single unit.
4. Balance the elements one at a time by using
coefficients. Do not attempt to the balance the
equation by changing the subscripts in the
chemical formula of a substance.
5. Check each atom or polyatomic ion to be sure
that the equation is balanced.

13. Four Basic Types of Chemical
Reactions
Most chemical reactions can be placed into one of four basic
types:
1. Decomposition Reactions
2. Synthesis/Combination Reactions
3. Single Displacement Reactions
• Combustion Reactions
4. Double Displacement Reactions
• Neutralization Reactions
• Precipitation Reactions

14. 1. Decomposition Reactions
A compound breaks into parts.
compound element + element
→
2H2O 2H
→ 2 + O2
Some decomposition complications with
heat:
Some acids, when heated,
decompose into an acidic oxide and
H2O.
H2SO4 SO
→ 3 + H2O

15. 1. Decomposition Reactions
• Metallic hydroxides, when heated,
decompose into a metallic oxide and H2O.
Ca(OH)2 CaO + H
→ 2O
• Metallic carbonates, when heated,
decompose into a metallic oxide and CO2.
Li2CO3 Li
→ 2O + CO2
• Metallic chlorates, when heated, decompose
into metallic chlorides and O2.
2KClO3 2KCl + 3O
→ 2

16. 2. Synthesis/Combination Reactions
• Elements are joined together.
element + element compound
→
2H2 + O2 2H
→ 2O
• Compounds are joined together
compound + compound compound
→ + oxygen
6CO2 + 6H2O C
→ 6H12O6 + 6O2

17. 3. Single Displacement Reactions
A single element replaces an element in a compound.
element + compound element + compound
→
Zn + 2HCl H
→ 2 + ZnCl2
Combustion Reactions
Ahydrocarbon(a compound containing only carbon
and hydrogen) combines with oxygen.
The products of combustion arealways carbon dioxide
and water.
hydrocarbon + oxygen carbon dioxide + water
→
CH4 + 2O2 CO
→ 2 + 2H2O

18. 4. Double Displacement Reactions
An element from each of two compounds switch places.
compound + compound compound + compound
→
H2SO4 + 2NaOH Na
→ 2SO4 + 2H2O
Neutralization Reactions
Special types of double displacement reactions that involve the
reaction between an acid and base to form a salt and water.
acid + base salt + water
→
Heat is usually given off in neutralization reactions.
A suspension of solid magnesium hydroxide in water is widely
used as an antacid to neutralize excess stomach acid:
acid + base salt + water
→
2HCl(aq) + Mg(OH)2(s) MgCl
→ 2(aq) + 2H2O(l)

19. 4. Double Displacement Reactions
Precipitation Reactions
Aqueous reactions that involve the formation of a
precipitate (solid).
soluble compound + soluble compound insoluble compound
→
2KI(aq) + Pb(NO3)2(aq) 2KNO
→ 3(aq) + ↓PbI2(s)
The physical state symbol (aq) says the reaction is taking
place in a water solution. The physical state symbol (s) says
the lead (II) iodide is a solid - therefore insoluble in the
solution.

20. Rules for Predicting Products of
Chemical Reactions
Here are a few important things to remember when
predicting products:
• The compounds form must be neutral ionic
compounds (which means pay attention to their
charges)
• Do NOT carry subscripts from the reactants to
the products.
• Always balance your equation LAST

21. Predicting Products of Combustion
Reactions
A hydrocarbon and oxygen (O2) indicate
combustion reaction.
If it is combustion, then just write H2O and CO2
as products
Then, balance the equation (can be tricky)
Examples:

22. Predicting Products of Displacement
Reactions
• A metal will not always replace
a metal in a compound
dissolved in water because of
differing reactivities
• An activity series can be used to
predict if reactions will occur
• To replace a metal, the other
metal must be MORE
REACTIVE
• Same applies for halogens

23. Predicting Products of Single
Displacement Reactions
• To predict the products: Replace the single element
with the corresponding element in the compound.
A metal will replace the cation in the compound
A non-metal will replace the anion in the compound
• If the element is more reactive than the one it attempts
to replace, then the reaction will be spontaneous and
exothermic.
• Otherwise, it will not be spontaneous and will be
endothermic therefore, NO REACTION.

25. Predicting Products of Double
Displacement Reactions
• If it is double replacement, then the cation and anions switch
places
• It is helpful to separate each compound into their cation and
anionic parts with their charges
• Then switch places, and criss cross the new compounds to
make sure they are the correct neutral compound formulas

26. Predicting Products of Double
Displacement Reactions
• AB and CD are both ionic compounds
• Separate each compound & write their charges
• Switch places and re-write new compounds
• Balance at the end

27. Predicting Products of Double
Displacement Reactions
• Not all double replacement reactions will occur
• In order for a double replacement reaction to take
place:
Both of the reactants must be soluble in water
If a compound contains at least one of the ions that is proven
soluble, then the compound will be at least moderately soluble
One product must be soluble and one product must be
insoluble
The insoluble product is the precipitate that forms when the
reaction takes place
Usually a precipitate is a solid, but it doesn't have to be

28. Solubility Table

29. Predicting Products of Double
Displacement Reactions