Ionic vs. Covalent Compounds and Solubility: Study Guide

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Unit: Ionic vs. Covalent Compounds and Solubility

Vocabulary and Key Concepts

This section introduces essential terms and definitions related to ionic and covalent compounds, solubility, and solution chemistry.

Ionic Compound: A chemical compound composed of ions held together by electrostatic forces termed ionic bonding. Typically formed between metals and nonmetals.
Covalent Compound: A compound where atoms share electrons, usually formed between nonmetals.
Solute: The substance dissolved in a solution.
Solvent: The substance that dissolves the solute, often present in greater amount.
Solution: A homogeneous mixture of two or more substances.
High Concentration: A solution with a large amount of solute relative to solvent.
Low Concentration: A solution with a small amount of solute relative to solvent.
Metal: An element that is lustrous, conducts electricity, and is malleable.
Nonmetal: An element that is not lustrous, has a low melting point, and does not conduct electricity well.
Polar Molecule: A molecule with an uneven distribution of charge, resulting in positive and negative poles.

Classifying Matter

Matter can be classified based on its composition and properties. Understanding the differences between elements, compounds, and mixtures is fundamental in chemistry.

Element: A pure substance consisting of only one type of atom.
Compound: A substance formed when two or more elements are chemically bonded.
Mixture: A combination of two or more substances that are not chemically bonded.

Order of Types of Matter (from most to least common): Elements, compounds, mixtures.

Comparison Table:

Type	Definition	Example
Element	Pure substance of one atom type	O2, Fe
Compound	Chemically bonded atoms	H2O, NaCl
Mixture	Physical blend of substances	Air, saltwater

Ionic vs. Covalent Compounds

Ionic and covalent compounds differ in their bonding, properties, and behavior in solution.

Ionic Bonds: Formed by the transfer of electrons from a metal to a nonmetal, resulting in positive and negative ions.
Covalent Bonds: Formed by the sharing of electrons between nonmetals.
Properties of Ionic Compounds:
- High melting and boiling points
- Conduct electricity when dissolved in water
- Usually soluble in water
Properties of Covalent Compounds:
- Lower melting and boiling points
- Do not conduct electricity in water
- May be soluble or insoluble in water

Example: NaCl (table salt) is ionic; H2O (water) is covalent.

Identifying Ionic and Covalent Compounds

Compounds can be identified as ionic or covalent based on their constituent elements.

Compound	Metal or Nonmetal	Ionic or Covalent Bond?
SO2	Nonmetal + Nonmetal	Covalent
F2	Nonmetal + Nonmetal	Covalent
MgBr2	Metal + Nonmetal	Ionic
CaO	Metal + Nonmetal	Ionic
H2O	Nonmetal + Nonmetal	Covalent
K2O	Metal + Nonmetal	Ionic
AlF3	Metal + Nonmetal	Ionic

Writing Chemical Formulas

Formulas for ionic and covalent compounds are written based on the elements involved and their ratios.

Ionic Compounds: Use the charges of ions to determine the ratio (e.g., NaCl, CaCl2).
Covalent Compounds: Use prefixes to indicate the number of atoms (e.g., CO2, H2O).

Bonding and Electronegativity

Bonds are classified based on the difference in electronegativity between atoms.

Ionic Bonds: Large difference in electronegativity (metal and nonmetal).
Covalent Bonds: Small or no difference in electronegativity (nonmetals).

Bond Formation:

Ionic: Transfer of electrons
Covalent: Sharing of electrons

Solubility and Solutions

Solubility refers to the ability of a substance to dissolve in a solvent. Solutions are classified by their concentration and saturation.

Soluble: Substance dissolves in solvent.
Insoluble: Substance does not dissolve.
Saturated Solution: Contains the maximum amount of solute that can dissolve at a given temperature.
Unsaturated Solution: Contains less than the maximum amount of solute.
Supersaturated Solution: Contains more solute than is normally possible at a given temperature.

Example: Adding more salt to water until no more dissolves creates a saturated solution.

Solubility Graphs

Solubility graphs show how the solubility of substances changes with temperature.

Most solids become more soluble as temperature increases.
Gases typically become less soluble as temperature increases.

How to Use a Solubility Graph:

Find the temperature on the x-axis.
Read the solubility (g solute/100 g water) on the y-axis.
Compare the amount of solute added to determine if the solution is saturated, unsaturated, or supersaturated.

Calculating Percent Mass of Solute in Solution

The percent by mass of a solute in a solution is calculated using the following formula:

Example: If 5 grams of MgCl2 are dissolved in 95 grams of water, the percent by mass is:

Application: Drinking Water Safety

Concentration of substances in water is often measured in parts per million (ppm) to determine safety for consumption.

Safe drinking water standards specify maximum allowable concentrations for various substances.

Example: If 0.013 grams of manganese are found in 1000 grams of water, the concentration in ppm is:

Summary Table: Properties of Ionic vs. Covalent Compounds

Property	Ionic Compounds	Covalent Compounds
Bond Type	Transfer of electrons	Sharing of electrons
Constituent Elements	Metal + Nonmetal	Nonmetal + Nonmetal
Melting/Boiling Point	High	Low
Electrical Conductivity (in water)	Conducts	Does not conduct
Solubility in Water	Usually soluble	Varies

Additional info: These notes expand on the original worksheet by providing definitions, examples, and formulas for key concepts in ionic and covalent bonding, solubility, and solution calculations. The tables and explanations are designed to help students prepare for exams and understand foundational chemistry topics.