Unit Notes
Acids, Bases and Solutions
Acids and Bases
Acids
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What is it? An acid is an ionic compound that produces positive
hydrogen ions when dissolved in water.
Properties? Acids taste sour, conduct electricity because they
consist of charged particles in solution, react with metals to
produce hydrogen gas, and turn blue litmus paper red. (Litmus
paper is an indicator, meaning it changes color when an acid or base
comes in contact with it)
Bases
 What is it? A base is an ionic compound that produces negative
hydroxide ions when dissolved in water.
 Properties? Bases taste bitter, feel slippery, conduct electricity and turn red litmus paper blue.
Strength of Acids and bases
 How is it determined? The strength of acids and bases is determined by the concentration of ions they produce
when dissolved in water.
 A stronger acid? It produces a greater concentration of hydrogen (H+) ions than a weaker acid (in water).
 A stronger base? It produces a greater concentration of hydroxide ions (OH-) than a weaker base (in water).
 The concentration of hydrogen ions in a solution is called acidity. It is measured by pH. A neutral substance has
a pH of 7. An acid has a pH lower than 7, and a base has a pH greater than 7.
Neutralization reactions
 When do they happen? The reaction of an acid and a base is called a neutralization reaction. It produces a salt
and water, both of which are neutral.
 Example? HCl (acid) + NaOH (base)  H2O (water) + NaCl (salt)
Importance of pH
 Acidity is an important factor for ALL living things (plants, fish, acid rain, lakes,
rivers)
Introduction to Solutions
Solutions
 What is it? A solution forms when a solute dissolves in a solvent.
 How does it dissolve? When a solute dissolves, it separates into individual
particles that spread evenly throughout the solvent.
 Does it matter what type of bond there is? Solutes with ionic bonds, such as table salt (NaCl),separate into
individual ions (Na+ and Cl-). Solutes with covalent bonds, such as glucose (C6H12O6), separate into individual
molecules.
 Why is water a universal solvent? It is polar and has positive and negatively charged ends, and this allows it to
break apart (dissolve) ionic compounds. It can’t dissolve everything!
Rate of Dissolving
 What affects the rate? The rate of dissolving is faster with stirring, a higher temperature, or greater surface area.
Many solutes are soluble in water because water is polar.
 Do solutes change the physical properties of solvents? They lower the freezing point and raise the boiling point
of solvents.
Solubility and Concentration
Solubility
 What is it? It is the amount of solute that can dissolve in a given amount
of solvent at a given temperature.
 How much solute can a solvent hold? A solution that contains as much
solute as can dissolve at a given temperature is saturated. A solution that
contains less solute than can dissolve at a given temperature is
unsaturated.
 What factors affect solubility? Temperature and pressure.
Concentration
 What is it? The amount of solute in a given amount of solution.
 How can you classify it? A dilute solution has a low concentration of solute. A concentrated solution has a high
concentration of solute.
Energy of Chemical Reactions
Endothermic reactions
 What is it? A reaction where it takes more energy to beak bonds in the reactants than is released when new
bonds form in the products.
 An endothermic reaction needs a constant input of energy to keep going.
Exothermic reactions
 What is it? A reaction where it takes less energy to break bonds in the reactants than is released when new
bonds form in the products.
 An exothermic reaction releases enough energy to keep going.
 Overall change there is no overall change in the amount of energy. Energy cannot be created or destroyed. This
is the law of conservation of energy.
Activation Energy
 What is it? The energy needed at the beginning of a reaction to bring reactants close together so they can react.
Reaction Rate
 What is it? How fast a reaction occurs.
 What affects it? Catalysts and the temperature, concentration, and surface area of reactants.
 What are catalysts? These are enzymes, a type of protein. It is a substance that increases the rate of a chemical
reaction but is not changed or used up in the reaction.