Balancing chemical equations

2.  Chemical equation - Describes a chemical change.
 Parts of an equation:
2Ag + H2S Ag2S + H2
Reactant Product
Reaction symbol

3.  Reactant - The chemical(s) you start with before the
reaction.
 Written on left side of equation.
 Product - The new chemical(s) formed by the
reaction.
 Right side of equation.

4.  Subscript - shows how many atoms of an element are
in a molecule.
 EX: H2O
 2 atoms of hydrogen (H)
 1 atom of oxygen (O)
 Coefficient - shows how many molecules there are of
a particular chemical.
 EX: 3 H2O
 Means there are 3 water molecules.

5.  2H2 + O2  2H2O

6.  In a chem. rxn, matter is neither created nor
destroyed.
 In other words, the number and type of atoms going
INTO a rxn must be the same as the number and type of
atoms coming OUT.
 If an equation obeys the Law of Conservation, it is
balanced.

7.  CH4 + O2  CO2 + H2O
Reactant Side Product Side
1 carbon atom
4 hydrogen atoms
2 oxygen atoms
1 carbon atom
2 hydrogen atoms
3 oxygen atoms

8. A Balanced Equation
 CH4 + 2O2  CO2 + 2H2O
Reactant Side Product Side
1 carbon atom
4 hydrogen atoms
4 oxygen atoms
1 carbon atom
4 hydrogen atoms
4 oxygen atoms

9. 1. Matter cannot be created or destroyed.
2. Subscripts cannot be added, removed, or changed.
3. You can only change coefficients.
4. Coefficients can only go in front of chem.
formulas...NEVER in the middle of a formula.
A few extra tips:
Try balancing big formulas first; save free elements for last.
If the same polyatomic ion appears on both sides of the
equation, it’s usually okay to treat it as one unit.
There is no one particular way to balance equations. Some
equations are harder to balance than others and might require
some creativity to solve.

10.  Balance the following equation by adjusting
coefficients.
reactants products
N
H
N2 + H2  NH3
2
2
1
3
2
2
6
3
6

11.  Balance the following equation by adjusting
coefficients.
KClO3  KCl + O2
reactants products
K
Cl
O
1
1
1
1
3 2
3
2
2
2
6 6
2
2
2

12.  Balance the following equation:
 C2H6 + O2  CO2 + H2O
4 6
7
2

13.  Balance the following equation:
 Fe + O2  Fe2O3
2
3
4

14. Chemical reactions are an integral part of
technology, of culture, and indeed of life
itself. Burning fuels, smelting iron, making
glass and pottery, brewing beer, and
making wine and cheese are among
many examples of activities incorporating
chemical reactions that have been known
and used for thousands of years.

15. Theory explains how collision between reactant molecules
may or may not result in a successful chemical reaction.
Based on this theory, not all collisions between the molecules
which result in the formation of products, only occur when the
following two conditions are met:
a. The colliding molecules should possess a minimum kinetic
energy known as activation energy, to start a chemical
reaction.
b. The reactant molecules should be in correct orientation
when they collide. Activation energy is needed to break the
bond between reactant molecules to form new bonds
leading to formation of products.

16. 1.Temperature
The higher the temperature, the more particles gain energy
and cause them to move faster. The faster the particles move,
there is an increasing tendency to collide frequently and
produce more energy. Through this activation energy is more
likely to exceed. As a result, there will be a higher rate of
successful reaction.
2. Concentration/ pressure
Concentration and pressure are normally considered as
factors because both of them refer to how many particles
there are per unit volume. When concentration/ pressure
increases, there will be more particles present per unit of
volume which makes collisions more frequent. As a result,
there will be a higher rate of successful reaction.

17. 3. Surface area
For a given mass of a solid, large lumps have
smaller surface area to volume ratios than smaller
lumps or powders. If a large lump is divided or ground
into a powder: the area of exposed surface increases.
The higher the surface area the higher the reaction
rate.
4. Catalysts
Catalysts are substances that speed up a reaction.

18. Catalyst decreases the activation energy and
it provides alternative pathways and this
means that there will be a higher proportion of
successful collisions. One of the most
common sources of catalyst is the transition
metals like Cobalt and Nickel.