STOICHIOMETRY
2
CHEMICAL EQUATIONS
AND
REACTION STOICHIOMETRY
by
Temple C. Eke
,BACKGROUND
Chemical equations are used to represent chemical reactions between
chemical substances. A chemical equation shows the chemical formulas and
the amounts of the reacting substances (reactants) and the chemical formulas
and the amounts of the substances formed (products).
Consider the equation:
.
The number written by the side of each substance represents the number of
moles of the substance involved in the reaction. Thus, moles of react
with mole of to form moles of .
Reaction stoichiometry deals with the quantitative relationships between
substances in chemical reactions. As a general rule, we make reference to the
proportion established in the balanced equation of the reaction.
Let us consider the general requirements for handling calculations
based on chemical equations.
MOLAR MASS AND NUMBER OF MOLES
The general method for finding the molar mass of a substance was
explained in the first part of this topic (Get and study STOICHIOMETRY 1:
CHEMICAL FORMULAS AND COMPOSITION STOICHIOMETRY by
Temple C. Eke).
On the other hand, the method of finding the number of moles of a
substance depends on the physical state of the substance.
Case 1: Solids and Gases
The number of moles of a pure solid or gas is given by the ratio of its given
mass to its molar mass.
.
In symbols,
.
Case 2: Aqueous Solutions
The number of moles of a substance in an aqueous solution can be found if
the molar concentration and the volume of the solution are known.
The molar concentration of a solution is the number of moles of the solute per
(per unit volume) of the solution.
Mathematically,
, .
In symbols,
where molar concentration in , and
volume of the solution in .
Example 1: Number of moles in an Aqueous Solution
Calculate the number of moles of sodium hydroxide present in of the
solution with a concentration of .
Solution:
Molar concentration of the solution, .
Volume of the solution, .
The number of moles, .
With , and , we have
.
Example 2: Number of moles in an Aqueous Solution
Find the number of moles present in of solution of
hydrochloric acid.
Solution:
In the calculation of the number of moles, the given volume must be
expressed in .
Molar concentration of the solution, .
Volume of the solution, .
The number of moles, .
With , and , we have
.
MOLAR VOLUME OF A GAS
2
CHEMICAL EQUATIONS
AND
REACTION STOICHIOMETRY
by
Temple C. Eke
,BACKGROUND
Chemical equations are used to represent chemical reactions between
chemical substances. A chemical equation shows the chemical formulas and
the amounts of the reacting substances (reactants) and the chemical formulas
and the amounts of the substances formed (products).
Consider the equation:
.
The number written by the side of each substance represents the number of
moles of the substance involved in the reaction. Thus, moles of react
with mole of to form moles of .
Reaction stoichiometry deals with the quantitative relationships between
substances in chemical reactions. As a general rule, we make reference to the
proportion established in the balanced equation of the reaction.
Let us consider the general requirements for handling calculations
based on chemical equations.
MOLAR MASS AND NUMBER OF MOLES
The general method for finding the molar mass of a substance was
explained in the first part of this topic (Get and study STOICHIOMETRY 1:
CHEMICAL FORMULAS AND COMPOSITION STOICHIOMETRY by
Temple C. Eke).
On the other hand, the method of finding the number of moles of a
substance depends on the physical state of the substance.
Case 1: Solids and Gases
The number of moles of a pure solid or gas is given by the ratio of its given
mass to its molar mass.
.
In symbols,
.
Case 2: Aqueous Solutions
The number of moles of a substance in an aqueous solution can be found if
the molar concentration and the volume of the solution are known.
The molar concentration of a solution is the number of moles of the solute per
(per unit volume) of the solution.
Mathematically,
, .
In symbols,
where molar concentration in , and
volume of the solution in .
Example 1: Number of moles in an Aqueous Solution
Calculate the number of moles of sodium hydroxide present in of the
solution with a concentration of .
Solution:
Molar concentration of the solution, .
Volume of the solution, .
The number of moles, .
With , and , we have
.
Example 2: Number of moles in an Aqueous Solution
Find the number of moles present in of solution of
hydrochloric acid.
Solution:
In the calculation of the number of moles, the given volume must be
expressed in .
Molar concentration of the solution, .
Volume of the solution, .
The number of moles, .
With , and , we have
.
MOLAR VOLUME OF A GAS
