(Acids/Bases) What to understand? pH – The pH of a solution is a measure of the concentration of Hydrogen ions H+ in that solution. pH Scale Hydrogen ion is a hydrogen atom that has lost its only electron. Acids releases hydrogen ions (H+ ) in water solutions. Bases releases hydroxide ions (OH- )in solutions.

Acids and Bases Definitions of Acids & Bases - There are three ways to define acids & bases: 1. Arrhenius- production of H3O+ and OH- *this is the general definition that we will use for now…. 2. Brønsted-Lowry- H+ donors & acceptors 3. Lewis- e- pair donators & acceptors

The Arrhenius definition: An acid is a substance that dissociates in water to produce hydrogen ions ( H+ ) A base is a substance that dissociates in water to produce hydroxide ions (OH- ) Examples: Hydrochloric acid sodium hydroxide Nitric acid potassium hydroxide Acetic acid magnesium hydroxide Sulfuric acid calcium hydroxide Carbonic acid barium hydroxide Phosphoric acid

HCl (aq) + H2O(l) → H3O+ (aq) + Cl- (aq) The Bronsted-Lowry Definition: An acid is any substance that can donate H+ ions. A base is any substance that can accept H+ ions. According to the Bronsted and Lowry, a molecule of HCl does not simple dissociate in water in a hydrogen ion (H+) and a chloride ion (Cl- ). Rather, it reacts with water to produce a hydronium ion (H3O+) and a chloride ion. HCl (aq) + H2O(l) → H3O+ (aq) + Cl- (aq)

Properties of Acids sour taste- remember that acetic acid (vinegar) & citric acid are sour, don’t EVER taste anything in the lab change pH paper- changes pH paper red or orange rxn w/ phenolphthalein - none reactivity with metals- metals react with metals by single replacement reactions to yield H2(g) and a salt ex. Ba(s) + H2SO4(aq)  BaSO4(aq) + H2(g)

react w/ bases by neutralization reactions- to make salts & water by a double replacement, the products are not sour, do not change pH paper, and do not react w/ metals ex. HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq) CaO + 2HCl -> HOH + CaCl2 are electrolytes- b/c they form ions in aqueous solution, they are electrolytes (conduct electricity) feeling- like water on unbroken skin, they sting on cuts

Properties of Bases- rxn w/ phenolphthalein – colorless to pinbitter taste- Have any of you ever tasted soap? change pH paper- bases change pH paper to blue bases are slippery react w/ acids by neutralization rxns- to yield salts & water by DR rxns are electrolytes- b/c they dissociate to form ions, they too conduct electrolytes

pH Scale

Acid Deposition SO2 is release into the atmosphere when coal and petroleum products are burned. Volcanic eruptions. In the atmosphere, sulfur dioxide can react with water to produce sulfurous acid. Both Sulfurous and sulfuric acid can fall out of the sky in liquid form as rain, sleet, or snow. Acid Deposition

Acid Rain When rain has a pH lower than 5.6. It is considered acidic Effects: 1. Damage buildings and statues. 2. Makes lakes and streams unsuitable for life. Equation: H2SO4 + CaCO3 → CaSO4 + H2O + CO2

Work on the following… Checking Up p.210 (1-4) Chem To Go p.212 (1-10)

Homework: Answer Acids and Bases Study Guide. (see copy)