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. 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. Write balanced chemical equations for simple reactions, given either an unbalanced equation or a verbal description.

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

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

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

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

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

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

Balancing Chemical Equations DO NOT change the subscripts! DO NOT change the subscripts! BUT, if you have a polyatomic ion like SO 4 2- (sulfate) this stays as one unit!!! 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: 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: Aqueous solutions: Solutions: (review) Solutions: (review) Solvent: Solvent: Solute: Solute:

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

Electrolytes and Nonelectrolytes Electrolyte: Examples: Examples:

Electrolytes and Nonelectrolytes Nonelectrolyte: Examples: Examples:

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

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

Solubility Table Solubility guidelines - soluble salts Solubility guidelines - soluble salts

Solubility Table Solubility guidelines - insoluble salts Solubility guidelines - insoluble salts

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

Chemical Equations for Aqueous Reactions When a covalently bonded material dissolves in water, what happens to the molecules? When a covalently bonded material dissolves in water, what happens to the molecules? NO IONS ARE FORMED!

Chemical Equations for Aqueous Reactions When an ionic solid dissolves in water, what happens to the compound? When an ionic solid dissolves in water, what happens to the compound? This type of reaction is called a dissociation reaction. This type of reaction is called a dissociation reaction.

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

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