1. A CIDS, B ASES, AND P H Chapter 8.1

2. O BJECTIVES Describe the ionization of strong acids in water and the dissociation of strong bases in water. Distinguish between solutions of weak acids or bases and solutions of strong acids or bases. Relate pH to the concentration of hydronium ions and hydroxide ions in a solution.

3. A CIDS Acid – any compound that increases the number of hydronium ions when dissolved in water. When acids dissolve in water, they ionize, which means that they form ions. Hydrogen ions (H+) attach to water to form hydronium ions (H ³O+) Indicator – a compound that can reversibly change color depending on the pH of the solution or other chemical change. Acids turn blue litmus paper red.

4. A CIDS Strong acids ionize completely – meaning that they form as many hydronium ions as possible. Strong acids dissolved in water conduct electricity very well. Electrolyte – a substance that conducts electricity when dissolved in water. Weak acids do not ionize completely – meaning that they do not form the maximum amount of hydronium possible.

5. A CIDS Any acid can be dangerous in a concentrated form. To be safe, always wear safety goggles, gloves, and a lab apron when working with concentrated acids. Properties of Acids: Sour taste pH < 7 Proton donors Acids are electrolytes

6. B ASES Base – any compound that increases the number of hydroxide ions when dissolved in water. Some bases contain hydroxide and others combine with water to form hydroxide. Hydroxide (OH-) ions are basically a water molecule minus a hydrogen atom. Bases turn red litmus paper blue. Bases have a higher concentration of hydroxide ions than hydronium ions.

7. B ASES Strong bases are ionic compounds that contain a metal ion and a hydroxide ion. These are sometimes called metal hydroxides. Strong bases dissociate in water, meaning they separate into individual ions. The hydroxide ion is pulled away from the metal ion when it is dissolved in water. Strong bases can conduct electricity when dissolved in water because ions are readily available. Bases can be just as dangerous as acids, and in some cases more dangerous. Bases attack living tissue very rapidly.

8. B ASES Not all bases contain hydroxide ions, some react with water to form hydroxide. Remember, hydroxide is basically a water molecule minus a hydrogen atom. Some bases react with water in such a way that a hydrogen atom separates from the water forming a hydroxide ion. Examine Figure 5 pg 260

9. W HAT IS P H? pH actually refers to “the power of Hydrogen”. pH refers to the concentration of the hydronium (H ³O+) ions in solution. pH – a value used to express the acidity or alkalinity of a solution. pH scale – a scale from 0 to 14 that indicates how much hydronium concentration is present in a solution.

10. P H S CALE Acids < 7 Bases > 7 7 on the pH scale is neutral (pure water). The closer the value to 7, the weaker it is. Black coffee – pH of 5 weak acid Antacid – pH of 8 weak base The further the value from 7, the stronger it is. Stomach acid – pH of 2 strong acid Ammonia – pH of 12 strong base

11. P H S CALE Each step on the pH scale represents a power of 10. For example, a pH of 4 is ten times stronger (has 10 times the hydronium ion concentration) than a pH of 5. While a pH of 3 is 100 times stronger (has 100 times the hydronium ion concentration) than a pH of 5.