2. •In a chemical reaction, a substance
is converted to one or more new
substances. Chemical reactions
follow the law of conservation of
mass. Wherein, no atoms are
created or destroyed they are just
rearranged. Chemical reaction is
presented through chemical
equations.
3. Steps in Balancing Chemical
Equation
•Step 1: Translate the statement.
All the substances, that react
during the change, called
reactants, are placed to the left
of a “yield arrow”, which points
to all substances produced,
called products.
4. • Step 2: Balancing the atoms. Begin balancing
the equation by trying different coefficients
to make the number of atoms of each
element the same on both sides of the
equation.
• Start with the most complex substance, the
one with the largest number of atoms or
different type of atoms.
• End with the least complex substance, such
an element by itself.
• Step 3: Adjust the coefficients. The smallest
whole number is preferred.
7. Write and balance the following.
1. silver plus sulfur yields silver sulphide
2. ammonium hydroxide produces ammonia
and water
3. zinc plus hydrochloric acid gives zinc chloride
and hydrogen
4. lead chloride plus potassium iodide gives lead
iodide plus potassium chloride
5. zinc plus copper sulfate gives zinc sulfate plus
copper
19. •The Mole (mol) is a unit to count
numbers of particles in atom.
•One mole (1 mol) contains
6.022x1023 entities called the
Avogadro’s number.
•1 mole of a substance represents a
fixed number of chemical entities
and has a fixed mass.
20. •Atomic mass is the mass of an atom
in atomic mass units (amu).
•Atomic mass of an element
expressed in amu is numerically the
same as the mass of 1 mole of
atoms of the element expressed in
grams. Thus, 1 atom 12C “weighs”
12 amu.
21. • Molar mass (M) of a substance is the mass per
mole of its entities (atoms, molecules, or
formula units). It has a unit of grams per mole
(g/mol).
• Monoatomic elements: molar mass is the
atomic mass in the periodic table.
• Molecular elements: Elements that occur as a
molecule (diatomic elements., eg O2, F2 ) You
must know the molar mass then multiply to the
number of moles.
• Compounds: The molar mass of a compound is
the sum of the molar masses of atoms of the
elements in the formula.
25. •SP 3. How many grams of Ag are in
0.0342mol of Ag?
•SP 4. How many Fe atoms are in
95.8g of Fe?
•SP 5. How many moles of carbon
are in 315mg of graphite?
•SP 6. What is the mass in grams of
3.22 x 1020 Mn atoms.
27. •Empirical formula is the simplest whole
number ratio of moles of each element
in the compound.
Steps in Determining Empirical Formula
Step 1: Determine the number of mole of
each element.
Step 2. Divide each with the smallest
number.
Step 3. Multiply with the smallest integer
to turn subscripts into whole number.
28. Determine the empirical formula of a
compound that has the following percent
composition by mass: K 24.75, Mn 34.77, O
40.51 percent
29. Molecular formula is the actual number
of moles of each elements in 1 mole of
compound.
30. •SP 9. Elemental analysis
shows that the compound has
40.0 mass % C, 6.71 mass %
H, and 53.3 mass % O. The
molar mass is 90.08g/mol.
Determine the empirical
formula of lactic acid and
molecular formula.
33. Chemical Reactions That Involve a
Limiting Reactant
•Limiting reactant is the one that
yields the lower amount of
product. It is the reactant that
limits the amount of the other
reactant that can react and thus
the amount of product that can
form. The reactant used up first
in the reaction.
34. •SP11. In one process, 124 g of Al are
reacted with 601 g of Fe2O3, according
to the following reaction below.
Calculate the mass of Al2O3 formed and
determine which is the limiting and
excess reactant.
