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Acids, Bases and Salts

Acids, Bases and Salts. Version 1.0. Acid Properties. sour taste change the color of litmus from blue to red. react with metals such as zinc and magnesium to produce hydrogen gas hydroxide bases to produce water and an ionic compound (salt) carbonates to produce carbon dioxide.

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Acids, Bases and Salts

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  1. Acids, Bases and Salts Version 1.0

  2. Acid Properties • sour taste • change the color of litmus from blue to red. • react with • metals such as zinc and magnesium to produce hydrogen gas • hydroxide bases to produce water and an ionic compound (salt) • carbonates to produce carbon dioxide. These properties are due to the release of hydrogen ions, H+, in water solution.

  3. Base Properties • bitter or caustic taste • a slippery, soapy feeling. • the ability to change litmus red to blue • the ability to interact with acids

  4. Svante Arrhenius was a Swedish scientist who lived from 1859-1927. • In 1884 he advanced a theory of acids and bases.

  5. An Arrhenius acid “is a hydrogen-containing substance that dissociates to produce hydrogen ions.” HA → H+ + A- acid

  6. An Arrhenius base is a hydroxide-containing substance that dissociates to produce hydroxide ions in aqueous solution. MOH → M+(aq) + OH-(aq) base

  7. An Arrhenius acid solution contains an excess of H+ ions. An Arrhenius base solution contains an excess of OH- ions.

  8. J.N. Bronsted (1897-1947) was a Danish chemist and T. M. Lowry (1847-1936) was an English chemist. • In 1923 they advanced their theory of acids and bases.

  9. A Bronsted-Lowry acid is a proton (H+) donor. A Bronsted-Lowry base is a proton (H+) acceptor.

  10. Bronsted-Lowry Base Bronsted-Lowry Acid proton acceptor proton donor H+ + H2O(l) → H3O+(aq) + Cl-(aq)

  11. hydrogen ion combines with water hydrogen ion does not exist in water a hydronium ion is formed

  12. Conjugate acid-base pairs differ by a proton. When an acid donates a proton it becomes the conjugate base. → HCl(g) Cl-(aq) acid base

  13. Conjugate acid-base pairs differ by a proton. When a base accepts a proton it becomes the conjugate acid. → H2O (l) H3O+(aq) base acid

  14. → HCl(g) + H2O (l) Cl-(aq) + H3O+(aq) acid base base acid Conjugate acid-base pairs differ by a proton.

  15. In 1923 G. N. Lewis developed a more comprehensive theory of acids and bases. • The Lewis theory deals with the way in which a substance with an unshared pair of electrons reacts in an acid-base type of reaction.

  16. A Lewis acid is an electron-pair acceptor. A Lewis base is an electron-pair donor.

  17. Lewis Acid Electron Pair Acceptor Electron pair donated to H+ Lewis Base Electron Pair Donor

  18. Lewis Acid Electron Pair Acceptor Electron pair donated to B Lewis Base Electron Pair Donor

  19. Reactions of Acids In aqueous solution, the H+ or H3O+ ions are responsible for the characteristic reactions of acids.

  20. Reaction with MetalsAcids react with metals that lie above hydrogen in the activity series of elements to produce hydrogen and an ionic compound (salt): acid + metal → hydrogen + ionic compound 2HCl(aq) + Ca(s)→ H2(g) + CaCl2(aq) 2H2SO4(aq) + Mg(s)→ H2(g) + MgSO4(aq)

  21. Reaction with Metals Oxidizing acids react with metals to produce water instead of hydrogen: 3Zn(s) + 8HNO3(dilute)→ 3Zn(NO3)2 (aq) + 2NO(g) + 4H2O(l)

  22. acid base salt acid base salt Reaction with Bases The reaction of an acid with a base is called a neutralization reaction. In an aqueous solution the products are a salt and water: HBr(aq) + KOH(aq)→ KBr(aq) + H2O(l) 2HNO3(aq) + Ca(OH)2(aq)→ Ca(NO3)2(aq) + 2H2O(l)

  23. acid metal oxide salt acid metal oxide salt Reaction with Metal Oxides In an aqueous solution the products are a salt and water. This type of reaction is closely related to that of an acid with a base: 2HCl(aq) + Na2O(s)→ KBr(aq) + H2O(l) 2H2SO4(aq) + MgO(s)→ MgSO4(aq) + H2O(l)

  24. acid carbonate salt acid carbonate salt acid carbonate salt Reaction with Carbonates Most acids react with carbonates to produce carbon dioxide, water and an ionic compound: 2HCl(aq) + Na2CO3(aq)→ 2NaCl(aq) + H2O(l) + CO2(g) H2SO4(aq) + MgCO3(s)→ MgSO4(aq) + H2O(l) + CO2(g) HCl(aq) + NaHCO3(aq)→ NaCl(aq) + H2O(l) + CO2(g)

  25. Carbonic acid (H2CO3) is not the product when an acid reacts with a carbonate because carbonate spontaneously decomposes into carbon dioxide and water. H2CO3(aq)→ CO2(g)+ H2O(l)

  26. acid base salt acid base salt The reaction of an acid with a base is called a neutralization reaction. In an aqueous solution the products are a salt and water: HBr(aq) + KOH(aq)→ KBr(aq) + H2O(l) 2HNO3(aq) + Ca(OH)2(aq)→ Ca(NO3)2(aq) + 2H2O(l)

  27. Lewis acid base base acid salt Amphoteric Hydroxides Hydroxides of certain metals are amphoteric, meaning they are capable of reacting as either an acid or a base: Zn(OH)2 + 2HCl(aq)→ ZnCl2(aq) + 2H2O(l) Zn(OH)2 + 2KOH(aq)→ K2Zn(OH)4(aq) + H2O(l)

  28. Reaction of NaOH and KOH with Certain Metals Some amphoteric metals react directly with the strong bases sodium hydroxide and potassium hydroxide to produce hydrogen: base + metal + water → salt + hydrogen 2KOH(aq) + 2Al(s) + 6H2O(l)→ 2KAl(OH)4(aq) + 3H2(g) Lewis acid 2NaOH(aq) + Zn(s) + 2H2O(l)→ Na2Zn(OH)4(aq) + 3H2(g) Lewis acid

  29. Salts can be considered compounds derived from acids and bases. They consist of positive metal or ammonium ions combined with nonmetal ions (OH- and O2- excluded). Chemists use the terms ionic compound and salt interchangeably. Salts are usually crystalline and have high melting and boiling points.

  30. Salt Formation The negative ion of the salt is derived from the acid. The positive ion of the salt is derived from the base. NaOH HCl acid base NaCl salt

  31. Ionization of Water

  32. H2O + H2O→H3O+ + OH- acid base acid base H2O →H+ + OH- → → → → hydroxide ion Water ionizes slightly. hydronium ion Water ionization can be expressed more simply as: [H3O+] or [H+] = 1.0 x 10-7 mol/L [OH-] = 1.0 x 10-7 mol/L Two out of every 1 billion water molecules are ionized.

  33. H2O →H+ + OH- → → Water ionizes slightly. hydronium ion [H3O+] or [H+] = 1.0 x 10-7 mol/L [OH-] = 1.0 x 10-7 mol/L hydroxide ion Water ionization can be expressed more simply:

  34. Introduction to pH

  35. pH is the negative logarithm of the hydrogen ion concentration. pH = -log[H+]

  36. Calculation of pH

  37. pH = this number without the minus sign. pH = -log[H+] [H+] = 1 x 10-5 when this number is exactly 1 pH = 5

  38. pH is between this number and next lower number (4 and 5). pH = -log[H+] The number of decimal places of a logarithm is equal to the number of significant figures in the original number. [H+] = 2 x 10-5 when this number is between 1 and 10 one significant figure ph = 4.7 one decimal place

  39. pH = -log[H+] The number of decimal places of a logarithm is equal to the number of significant figures in the original number. [H+] = 2 x 10-5 when this number is between 1 and 10 one significant figure pH is between this number and the next lower number (between 4 and 5). ph = 4.7 one decimal place

  40. What is the pH of a solution with an [H+] of 1.0 x 10-11? 2 significant figures pH = - log(1.0 x 10-11) pH = 11.00 2 decimal places

  41. What is the pH of a solution with an [H+] of 6.0 x 10-4? 2 significant figures log[H+] = log 6.0 x 10-4 = -3.22 pH = - log[H+] = -(3.22) = 3.22 2 decimal places

  42. What is the pH of a solution with an [H+] of 5.47 x 10-8? 3 significant figures log[H+] = log 5.47 x 10-8 = -7.262 pH = - log[H+] = -(7.262) = 7.262 3 decimal places

  43. The pH scale of Acidity and Basicity 15.4

  44. Neutralization

  45. HCl(aq) + KOH(aq)→ KCl(aq) + H2O(l) acid base salt Neutralization: The reaction of an acid and a base to form a salt and water.

  46. Titrations

  47. titration: The process of measuring the volume of one reagent required to react with a measured mass or volume of another reagent.

  48. 42.00 mL of 0.150 M NaOH solution is required to neutralize 50.00 mL of hydrochloric acid solution. What is the molarity of the acid solution? acid base salt HCl(aq) + NaOH(aq)→ NaCl(aq) + H2O(l) Convert mL of NaOH to liters of NaOH The equation for the reaction is Calculate the liters of NaOH that react. The unit of volume when using molarity is liters. Calculate the moles of NaOH that react.

  49. 42.00 mL of 0.150 M NaOH solution is required to neutralize 50.00 mL of hydrochloric acid solution. What is the molarity of the acid solution? acid base salt HCl(aq) + NaOH(aq)→ NaCl(aq) + H2O(l) The equation for the reaction is The mole ratio of HCl to NaOH is 1:1 The moles of NaOH that react equals the moles of HCl that react. 0.00630 mol NaOH react. 0.00630 mol HCl react. The molarity of the HCl solution is

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