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Acids and Bases

Acids and Bases. Acids. An acid is a compound that ionizes and increases the number of hydrogen ions (H+) when dissolved in water. An acid contains H as a cation in the compound. - Ex. HCl, H 2 SO 4 , HF H + ions interact with water to form a H 3 O + ion , called a hydronium ion.

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Acids and Bases

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  1. Acids and Bases

  2. Acids • An acid is a compound that ionizes and increases the number of hydrogen ions (H+) when dissolved in water. • An acid contains Has a cation in the compound. • - Ex. HCl, H2SO4, HF • H+ ions interact with water to form a H3O+ion, called a hydronium ion.

  3. Properties of Acids • Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) • Taste sour • Corrode metals • Good Electrolytes • React with bases to form a salt and water • pH is less than 7 • Turns blue litmus paper to red “Blue toRed - ACID”

  4. Use of Acids • Citric acid and ascorbic acid (Vitamin C) are found in orange juice • Carbonic acid and phosphoric acid give a “bite” to soft drinks • Acids in your stomach aid in digestion • Sulfuric acid is the most widely used industrial acid in the world. It is used in making metals, paper, paints, and fertilizers.

  5. Bases A base is: • Any compound that ionizes in water to give an OH- ion – Hydroxide Ion.

  6. Properties of Bases • Produce OH- ions in water • Taste bitter, chalky • Are electrolytes • Feel soapy, slippery • React with acids to form salts and water • Does not react with Group I & II metals • pH greater than 7

  7. Use of Bases • Bases are used in soaps (remember, bases are slippery) • Bases are used to make paper, in oven cleaners, and to unclog drains • Ammonia is a base and is used in many household cleaners

  8. Some Common Bases KOH potassium hydroxide - liquid soap Ba(OH)2 barium hydroxide - stabilizer for plastics Al(OH)3 aluminum hydroxide - Maalox (antacid)

  9. Strength of Acids The strength of an acid or base depends on how completely it ionizes in water. • A strong acid (H+ donor) is one that almost completely ionizes in water to form H3O+. • A weak acid (H+ donor) is one that only partially ionizes in water. Do not confuse Strong with ConcentratedAcid: • Strong acid refers to how much an acid ionizesin water to form hydronium ions (H3O+) • Concentration is the amount of acid (solute) that is put in water (solvent)

  10. Detecting Acids & Bases • You can detect an acid or base using an indicator. • Indicatorsare organic compounds that changes color depending on whether the solution is acidic or basic. • Cabbage Juice and Litmus (pH) paper are examples of acid/base indicators: • Acids turns blue litmus paper to red: “Blue toRed - ACID” • Bases turns red litmus paper to blue: “Basic = Blue”

  11. Measuring Acidity & Basicity • Hydrogen ion concentration [H+] of solutions are very small numbers. • Because of that, a pH scale has been developed to measure a solutions acidity or basicity.

  12. pH • Indicates the acidity [H3O+] of the solution: pH = - log [H3O+] • From the French pouvoir hydrogene (“hydrogen power” or “power of hydrogen”)

  13. pH Range 0 1 2 3 4 5 6 7 8 910 11 12 13 14 Neutral [H+]>[OH-][H+] = [OH-][OH-]>[H+] Acidic Basic H2O The smaller the pH value, the more acidic the solution is.

  14. Increasing Basicity Increasing Acidity pH is a measure of a solutions acidity • The pH scale is a logarithmic scale (power of 10) • The pH scale range is 0 to 14. • pH of 7 is neutral • The smaller the pH value, the more acidic the solution Blood

  15. Buffers Buffer:A buffer solution is one which resists changes in pH when small quantities of an acid or an alkali are added to it. How do buffer solutions work? A buffer solution contains ions that remove hydrogen ions or hydroxide ions that are added to the solution, countering a change in pH. • Acid buffers are usually weak bases. • Base buffers are usually weak acids.

  16. Acid/Base Reactions Neutralization:is the chemical reaction between an acid & base in a water solution leading to a neutral (pH = 7) solution. Titration:The process of determining the strength of an unknown acid/base using another acid/base of known concentration • Salt:is the product formed from the reaction of an acid with a base: • 2HCl + 2NaOH  2NaCl + H2O • AcidBase Salt Water • The product of an acid/base reaction is a salt and water!

  17. Acid/Base Titration • 1. Select indicator to add to unknown solution • 2. Add basic or acidic solution with known concentration to the solution from the buret. • An acid-base reaction occurs with the unknown solution in the flask. • Indicator change in colorshows when the solution acidity = basicity. • This is called: • NEUTRALIZATION. Titration Set-up • Phenolphthalein is a common acid/base titration indicator. • Phenolphthalein is colorless (clear) in an acidic solution, and turns bright pink in a basic solution.

  18. Naming Bases Bases are compounds that contain the polyatomic ion hydroxide (OH-1) Bases are named like other ionic polyatomic compounds: 1. Determine if the metal (the first element) has multiple oxidation states (charge numbers). 2. If NO, write the name of the metal. 3. If YES, write the name of the metal followed by its oxidation state (charge) in Roman Numerals. 4. Write the name of the Polyatomic Ion -“hydroxide”.

  19. Writing Base Formula's 1. Determine the oxidation states (charge number) of each element. If metal has more than one oxidation state, it will be shown as Roman Numerals in parentheses! 2. Do the oxidation states (charges) add together to make 0? 3. If YES, write the symbol for each element (metal first) and your are finished! 4. If NO, use the criss-cross method and determine the subscripts for each element. 5. Write the symbol for each element with their corresponding subscript number, making sure to put parenthesis around the hydroxide polyatomic ion.

  20. Naming Bases - calcium hydroxide - copper(I) hydroxide - Al(OH)3 - NH4OH - Ni(OH)3 • - Ca(OH)2 • - CuOH • - aluminum hydroxide • - ammonium hydroxide • - Nickel (III) hydroxide

  21. Naming Acids Acids are compounds that contain hydrogen (H) as its first element. • There are two types of acid compounds: • Binary Acids • Ternary Acids

  22. Binary Acids Binary acids are acids comprised of hydrogen and a single element • To name a binary compound you use the following format: • 1. Add the name “hydro” before the non-hydrogen element. • 2. Add the ending “ic” to the end of the non-hydrogen element. • 3. Add the word “acid” to the name generated by 1 & 2 above. - Hydrochloric Acid - Hydrobromic Acid - HI - HF - HCl - HBr - Hydroiodic Acid - Hydrofluoric Acid

  23. Ternary Acids Ternary acids are acids comprised of hydrogen and a polyatomic ion. • To name a ternary compound you use the following format: • 1. If the name of the polyatomic element ends in “-ate” then “-ic” is added to the end of the root name followed by the word “acid”. • 2. If the name of the polyatomic element ends in “-ite” then “-ous” is added to the end of the root name followed by the word “acid”. - Nitric Acid (base is nitrate) - Nitrous Acid (base is nitrite) - H2SO4(base is sulfate) - H2SO3 (base is sulfite) - HNO3 - HNO2 - Sulfuric Acid - Sulfurous Acid “In the PHS cafeteria, I -ATE something -ICky”

  24. Acids • Remember: • The Prefix “Hydro” is only used with Binary Acids

  25. Give Acid Formula or Name a) HClO3 b) H2S c) HBr d) H3PO3 e) HIO3 f) hydrochloric acid g) sulfuric acid h) chlorous acid i) hydrofluoric acid a) chloric acid b) hydrosulfuric acid c) hydrobromic acid d) phosphorous acid e) iodic acid f) HCl g) H2SO4 h) HClO2 i) HF

  26. Acid Nomenclature Flowchart

  27. Acid Nomenclature Review • HBr (aq) • H2CO3 • H2SO3  hydrobromic acid  carbonic acid  sulfurous acid

  28. pH

  29. Pure Water is Neutral Pure water contains equal amounts of ions: H3O+ and OH-: H2O + H2O H3O+ + OH- For aqueous solutions, the product of the [H3O+] and [OH-] equals 1 X 10-14 M2 : [H3O+] [OH-] = 1.0 X 10-14 M2 Kw = This equation is called the ion-product constant for water (Kw).

  30. H3O+ OH- Concentration Ion Product Constant of Water - Kw [ ] = Molar concentration Kw = 1 x 10-14 M2 = [ H3O+ ] [ OH- ] Kw = 1 x 10-14 M2 =[1 x 10-7][1 x 10-7] Pure water contains equal amounts of ions: H3O+ and OH- This is a neutral solution!

  31. Aqueous Solutions • Not all solutions are neutral – i.e., the amount of [H3O+] & [OH- ] may not be equal! • In any aqueous solution, the amount of [H3O+] & [OH- ] are interdependent – as the concentration of one goes up, the concentration of the other goes down.

  32. H2O H3O+ Concentration OH- Acids • Increase [H+] • HCl (g) H3O+ (aq) + Cl- (aq) • More [H3O+] than water > 1 x 10-7M • As H3O+ increases, OH- decreases [H3O+] > [OH-]

  33. H2O OH- Concentration H3O+ Bases • Increase the hydroxide ions (OH-) • NaOH(s) Na+ (aq) + OH- (aq) • More [OH-] than water, [OH-] > 1 x 10-7M • When OH- increases, H3O+ decreases [OH] > [H3O+]

  34. pH • Indicates the acidity [H3O+] of the solution: pH = - log [H3O+] • From the French pouvoir hydrogene (“hydrogen power” or “power of hydrogen”)

  35. pH scale • The scale for measuring the hydronium ion concentration [H+] in any solution must be able to cover a large range. A logarithmic scale covers factors of 10. A solution with a pH of 1 is 10 times stronger than a solution with a pH of 2. • A solution with a pH of 1 has [H+] of 0.1 mol/L or 10-1 • A solution with a pH of 3 has [H+] of 0.001 mol/L or 10-3 • A solution with a pH of 7 has [H+] of 0.0000001 mol/L or 10-7

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