Stoichiometry is a section of chemistry that involves using relationships between reactants and/or products in a chemical reaction to determine.

STOICHIOMETRY

I

Stoichiometry is a section of chemistry that involves using relationships between reactants and/or products in a chemical reaction to determine.

Balancing

In chemistry, chemical reactions are frequently written as an equation, using chemical symbols.

.

Reactants to Products

A chemical equation is like a recipe for a reaction so it displays all the ingredients or terms of a chemical reaction

A + B → C + D

2Na

+2HCl

→2NaCl

+H

In the equation, the elements present in reaction

are represented by chemical symbols. Based on the

Law of Conservation of Mass, which states that is

neither created nor destroyed .

Stoichiometric Coefficients

In a balanced reaction, both sides of the equation have the same number of elements.

This stoichiometric coefficients are useful since they establish the mole ratio between reactants and products. In the balanced equation:

2Na

+2HCl

→2NaCl

+H

2Na

+2HCl

→2NaCl

+H

A balanced equation ultimately has to satisfy two conditions.

1-The numbers of each element on the left and right side of the equation must be equal.

2-The charge on both sides of the equation must

be equal.

EXAMPLE

What is the molar mass of H

O?

SOLUTION

Molar mass = 2×(1.00g/mol)+ 1×(16.00g/mol)

= 18.00 g/ mol

Molarity

Molarity (moles/L) establishes a relationship between moles and liters.

Given volume and molarity, it is possible to

calculate mole or use moles and molarity to

calculate volume.

EXAMPLE

How much 5 M stock solution is needed to prepare 100 mL of

2 M solution?

Determining Empirical Formulas

An empirical formula can be determined through

chemical stoichiometry by determining which

elements are present in the molecule and in

what ratio.

Determining Molecular Formulas

To determine a molecular formula, first determine the empirical formula for the

compound as shown in the section above and then determine the molecular mass

experimentally.

Oxidation - Reduction Reactions

An oxidation-reduction (redox) reaction is a

type of chemical reaction that involves a

transfer of electrons between two species. The

reduced half gains electrons and the oxidation

number decreases, while the oxidized half loses

electrons and the oxidation number increases.

Disproportionation Reactions

In some redox reactions a single substance can be both oxidized and reduced. These are known as disproportionation reactions, with the

following general equation:

2A → A

+ A