Acids and Bases Acids O Acids are compounds that add (H +) ions to water when in a solution. H+ Cl- H+ In Water Cl- O HCl: a very strong acid. In water it breaks up (dissociates) and adds H+ to the water. Bases O Bases are compounds that add (OH-) ions to when in a solution. water Na+ H+ Na+ O2- In water O2- H+ O NaOH: a very strong base. In water it breaks up (dissociates) and adds OH- to the water. Common Acids O Many foods are acidic: Tomatoes Lemons Oranges Limes Apples vinegar O Acids taste sour and feel squeaky when you rub them between your fingers Common Bases O Many cleaners are basic: Soap Bleach ammonia (Windex) O Bases taste bitter and feel slippery when you rub them between your fingers Question #1 O Are antacids acids or bases? O Why? Safety O Acids are corrosive! They can burn your skin or eyes. O Bases are caustic! They can burn your skin or eyes. O Why do you think the safety sign for acids and bases is the same sign? Other Terms O Strong acids and bases— ionize (dissolve) completely in water, adding many ions to the water O Weak acids and bases—do not ionize (dissolve) completely in water, adding fewer ions to the water. The pH Scale Litmus Paper O Acids are indicated by a Red color. O If Red litmus paper is dipped in an acid it will stay Red O If Blue litmus paper is dipped in an acid it will turn Red Litmus Paper O Bases are indicated by a Blue color. O If Blue litmus paper is dipped in a base it will stay blue O If Red litmus paper is dipped in a base it will turn Blue Question #2! O What is the difference between the pH scale and litmus paper? Acid-Base Reactions: Neutralization O Neutralization Reaction: When acids and bases are mixed together, they neutralize each other. If an equal concentration of acid and base are mixed, they make a neutral solution of a salt and water H+ H+ O2- O2- H+ HCl + NaOH —> H2O + NaCl Acid Base Water Salt H+ Titration (Lab Process) O The lab process where this is studied is called titration and it uses a piece of glassware called a buret. Acid Rain O Acid Rain: Plants and animals need water close to neutral (pH 7) to survive. O Due to pollution from industries and cars, rain in certain areas can be acidic. Rain less than pH 5.6 is called acid rain. O Acid rain can kill plants, cause asthma, and other physical problems. O Because statues and landmarks are made of limestone (a base), acid rain will also slowly destroy them. Acid Rain (cont) O The Roman ruins, the pyramids of Egypt, and other treasures of the world are slowly being reacted away by acid rain. O More damage has been done in the last century than in the last 2,000 years. Acid Rain (cont) O Why do you think there has been more damage from acid rain in the last 100 years? Let’s See What You Know… Letter B D C A Matching 1. Acid 2. Base 3. Neutral 4. Neutralize A. To mix acids and bases to cancel each other out and make water and salt B. A compound that adds H+ ions to water C. Equal number of H+ and OH- ions; water is an example D. A compound that adds OH- ions to water. E 5. Acid Rain E. When pollution causes rain to have a pH less than 5.6. F 6. pH F. The measure of how acidic or basic a solution is H 7. Salt Water G. A compound that adds a few OH- ions to water 8. Strong Acid H. The product of a neutralization reaction between an acid and a base G 9. Weak Base I. A compound that adds a few H+ ions to water I 10. Weak Acid J. A compound that adds a lot of H+ ions to water. J Part II…. Is it an Acid or a Base? Circle the acids and underline the bases 11. HCl 17. H2CO3 23. apple juice 12. Mg(OH)2 18. NaOH 24. lemonade 13. H3PO4 19. Al(OH)3 25. soap 14. KOH 20. HBr 26. laundry detergent 15. Ca(OH)2 21. H2SO4 27. soft drinks 16. LiOH 22. H2O 28. bathroom cleaner Part III Acids or Bases? Identify the following with an A for Acid or B for Base 29. pH of 1 to 7 30. Feels slippery 31. pH of 7 to 14 32. Has more OH- ions 33. Has more H+ ions 34. Tastes sour A B B B A A TAKS Practice 1 A student wearing goggles, gloves, and an apron begins a simple activity to determine the pH of corrosive solutions. Before the activity, what other safety measures should the student follow? A Identify the locations of eye wash, shower, and fire equipment B Check and set clocks and record the beginning time C Review the proper method of fire-polishing glass tubing D Arrange the equipment in the work area alphabetically TAKS Practice 2 Hard water has a pH higher than 7 and an abundance of calcium and magnesium salts. Which of the following would be the best cleaning solution for removing hard-water residue from drinking glasses? A A mild acid such as vinegar B A strong solution such as ammonia C A hot solution such as baking soda in boiling water D A strong base such as sodium hydroxide TAKS Practice 3 Two clear solutions are placed in separate beakers. The first solution has a pH of 4, and the pH of the second solution is unknown. If the two solutions are mixed and the resulting pH is 5, the second solution must have – A fewer suspended solids B a lower temperature C more dissolved salt (NaCl) particles D a higher concentration of OH-ions TAKS Practice Properties of Some Solutions Solution Electrical Conductivity of Solution Original Color of Litmus Paper 1 2 3 4 Very high Low Moderate Very high Red Blue Red Blue Color of Litmus Paper After Dipping in Solution Blue Red Red Red pH 10.0 6.5 5.4 2.0 4 The table shows data from an investigation designed to find a liquid solution that is both an acid and a strong electrolyte. Based on the data, a solution that is both an acid and a strong electrolyte is – A Solution 1 B Solution 2 C Solution 3 D Solution 4 Venn Diagram of Acids and Bases O At least 3 points about Acids and Bases O At least 2 points about what they have in common