Aim: How can we describe the properties of acids and bases? Do Now: Take out a calculator and reference tables. Refer to tables K and L in your reference tables. What do those tables tell you?

What are acids? An Arrehnius acid is a substance that has a hydrogen which it will give off in an aqueous solution to make a H+ ion. Examples: HCl  H+(aq) + Cl-(aq) HBr  H+(aq) + Br-(aq) In these solutions, the H+ is the only positive ion in the solution. The H+ is believed to be unable to exist as an isolated proton so it bonds covalently with H2O to form H3O+ ions.

Characteristics of Acids Dilute solutions of acids have a sour taste (think lemon juice, vinegar (acetic acid), etc…). Acidic solutions can conduct an electric current. Substances that conduct electricity are called electrolytes. The ability of a solution to conduct electricity depends on the concentration of electrolytes. If a solution is a good conductor, it is called a strong acid. If it is a poor conductor, it is called a weak acid.

Characteristics of Acids 3. Acids react with bases to form water and a salt. This type of reaction is called a neutralization reaction. They are a type of double replacement reaction. The salt formed is an ionic substance composed of a partially charged positive ion and, a negative ion (other than a hydroxide). 4. Acids react with certain metals to produce hydrogen gas. Which metals will react to produce a salt and hydrogen gas? (Check Table J) 5. Acids cause acid-base indicators to change color.

What are bases? An Arrhenius base has an OH attached to it which it will dissociate in aqueous solution as an OH- ion. Examples: NaOH  Na+(aq) + OH-(aq) KOH  K+(aq) + OH-(aq) In these solutions, OH- is the only negative ion in the solution.

Characteristics of Bases Bases have a bitter taste. Bases have a slippery or soapy feeling (think bleach etc…). Bases conduct an electric current. A base that has a high concentration of ions will conduct electricity better and is called a strong base. A base with a low concentration of ions will be a poor conductor and is called a weak base. Bases react with acids to produce water and a salt. Bases cause acid-base indicators to change color.

Why are some acids and bases stronger than others? It depends on how much the acid or base will ionize. An acid that ionizes completely (meaning every molecule dissociates when in solution) is called a strong acid. If only some of the acid dissociates, the acid is weaker. The same is true of bases. ***Note*** Strong acids tend to be weak bases, and weak acids tend to be strong bases.

How can acids be different from each other? Some acids will yield only one H+ ion. These are called monoprotic acids. An example is HCl. Some acids will yield two H+ ions. These are called diprotic acids. These acids ionize in two steps. An example is H2SO4. H2SO4  H+ + HSO4- HSO4-  H+ + SO42- Some acids will yield three H+ ions. These acids are called triprotic acids.

Naming Acids Binary acids – composed of Hydrogen and one other element. The names of binary acids begin with Hydro followed by the name of the other element modified to end with –ic. Example: Hydrogen chloride (HCl) is normally a gas. When it dissolves in water, it become hydrochloric acid.

Naming Acids Ternary acids - molecular substances that produce hydrogen ions when dissolved in water. They consist of a polyatomic ion containing oxygen such as nitrate (NO3-) or sulfate (SO42-). When naming a ternary acid, the anion suffixes –ate and –ite are replaced by suffixes –ic and -ous respectively. Example: H2SO4 becomes sulfuric acid Example: H2SO3 becomes sulfurous acid

Naming Bases When naming a base, the name of the positive ion is not changed. The name of the base will end with hydroxide. Example: Ca(OH)2 is called calcium hydroxide. Example: NaOH is called sodium hydroxide.

A quick way to recognizing acids and bases Look at Tables K and L. Where do you see the H on the acids? Where do you see the H on the bases? Generally, acids have the H on the left of their chemical formulas, and bases have the H on the right. Exceptions: Some organic compounds have a group at the end called carboxyl groups (-COOH) which look like a base but are really an acid. Also, alcohols are chains of carbon that have an OH- attachment but do not ionize.

Activity/Homework Review Book Pages 177-178. Copy and answer #1-15