CHEM 5013
Applied Chemical Principles
Chapter Three
Professor Bensley
Alfred State College

Chapter Objectives


Explain balancing a chemical reaction as an application of the law of conservation of mass.
Write balanced chemical equations for simple reactions, given either an unbalanced equation or a verbal description.

Chapter Objectives


Distinguish between electrolytes and nonelectrolytes and explain how their solutions differ.
Describe the species expected to be present (ions, molecules, etc.) in various simple solutions.

Writing Chemical Equations

What does a Chemical equation represent?

Reactants form products

Writing Chemical Equations



Reactants and products are represented by chemical formulas.
The phase for the compounds must be given.
Example:

Balancing Chemical Equations

The Law of Conservation of Matter
(Conservation of Mass):

Balancing Chemical Equations



Chemical equations balanced via inspection.
Numbers used to balance chemical equations are called coefficients.
Example: Burning of natural gas (methane)
(Combustion Reaction)

Example: Write the complete balanced combustion reaction of propane.

Balancing Chemical Equations

We normally use the smallest whole numbers possible as coefficients.

Trial and Error

HINT – Balance the atoms first that occur in only one substance on each side

Balancing Chemical Equations

DO NOT change the subscripts!

BUT, if you have a polyatomic ion like
SO
4
2(sulfate) this stays as one unit!!!

So to balance, place a new subscript outside the parenthesis as in:

Balancing Chemical Equations
Write balanced equations for:
1.
Sodium hydroxide reacting with carbon dioxide to form water and sodium carbonate
2.
Sodium phosphate reacting with magnesium chloride to form magnesium phosphate and sodium chloride

Solutions, Solvents, and Solutes


Aqueous solutions:
Solutions: (review)

Solvent:

Solute:

Ions in Aqueous Solution




Dissolve NaCl in water.
Na + ions and Cl ions go into solution as freely moving ions
What happens when you apply an electrical source
(battery) to the solution?
What about pure water?

Electrolytes and Nonelectrolytes

Electrolyte:

Examples:

Electrolytes and Nonelectrolytes

Nonelectrolyte:

Examples:

Strong and Weak Electrolytes

Strong electrolyte:

Example:

Weak electrolyte:

Example:




Solubility -
Soluble -
Examples:
Solubility Rules

Insoluble -

Examples:

Solubility Table

Solubility guidelines - soluble salts

Solubility Table

Solubility guidelines - insoluble salts

EXAMPLE
Determine whether or not the following compounds are soluble or insoluble in water.
1) NaBr
2) Ba(OH)
2
3) Calcium carbonate


Chemical Equations for Aqueous
Reactions

When a covalently bonded material dissolves in water, what happens to the molecules?
C
6
H
12
O
6
(s)  C
6
H
12
O
6
(aq)


Chemical Equations for Aqueous
Reactions


When an ionic solid dissolves in water, what happens to the compound?
This type of reaction is called a dissociation reaction.
NaCl (s)  Na + (aq) + Cl (aq)

Molecular and Ionic Equations


Remember chemical equations?
When ions are involved, we can write them in three forms:

1)


2)
3)


Example:
Called metathesis or precipitate or double substitution reactions.

Molecular and Ionic Equations

Molecular Equation:

Complete Ionic Equation:

Net Ionic Equation:

Spectator Ions:

Example
Write a net ionic equation for the molecular equations below:
KCl (aq) + AgNO
3
(aq)  KNO
3
(aq) + AgCl (s)
Potassium Chloride + Calcium Hydroxide