In this presentation you will:

1. Salts In this presentation you will: • explore the properties and reactions of salts Next >

2. Introduction Salts form ions in aqueous solution. Salts have both physical and chemical properties. Salts have anionic and cationic components. Next >

3. Salts Salts are neutral compounds containing positively charged cations and negatively charged anions, held together by ionic bonds. Salts, therefore, are all ionic substances. Almost all salts are solids at room temperature. Some are colorless, but many others exist in different colors. Some also have distinctive smells and tastes. Next >

4. Salt Properties Salts naturally form crystal lattice structures in the solid phase and, as a result, tend to have very high melting points (>800 °C). The structure of a crystal lattice depends upon: • the ratio of positive and negative ions in the ionic compound • the sizes and charges of the ions involved • other atoms that are present, often including water molecules Next >

5. Question 1 What type of chemical bonding is found in solid salts? A) Covalent bonding B) Metallic bonding C) Crystal bonding D) Ionic bonding Next >

6. Question 1 What type of chemical bonding is found in solid salts? A) Covalent bonding B) Metallic bonding C) Crystal bonding D) Ionic bonding Next >

7. Ionic Ratios The simplest unit of a crystal structure, or unit cell, is a set of atoms arranged in a particular way. This is repeated in an ordered arrangement in all three dimensions of the lattice. Next >

8. Simple cubic crystal Face-centered crystal Ionic Ratios In a simple crystal where ions of similar size combine in a 1:1 ratio, each cation is bordered by one anion in a simple cubic structure. Where the two ions are of different sizes, face- or body-centered structures are more common. Next >

9. + Fe2O3 boiling point = 1565°C NaCl boiling point = 800°C Ionic Ratios As salts are neutral compounds, the ions must be arranged in a fixed ratio to give zero overall charge. Iron(III) oxide, a component of rust, has the formula Fe2O3 because two Fe3+ iron ions must combine with three O2- oxygen ions to form a stable salt. Generally, compounds with more highly charged ions will have higher melting points as more energy is needed to dissociate the ions (break the crystal lattice structure). Next >

10. Question 2 "Because of the crystal lattice structure, salts tend to have very high melting points, often in excess of 800 °C." Is this statement true or false? Answer True or False. Next >

11. Question 2 "Because of the crystal lattice structure, salts tend to have very high melting points, often in excess of 800 °C." Is this statement true or false? Answer True or False. True Next >

12. Question 3 Why do compounds with more highly charged ions have higher melting points? A) Because they dissolve more readily B) Because more energy is needed to dissociate the ions C) Because the heat is conducted away as electricity Next >

13. Question 3 Why do compounds with more highly charged ions have higher melting points? A) Because they dissolve more readily B) Because more energy is needed to dissociate the ions C) Because the heat is conducted away as electricity Next >

14. Physical Properties In addition to their high boiling points and crystal structures, most salts tend to exhibit the following properties: • they are hard and impossible to compress • most are soluble in water and other inorganic solvents • they are electrolytes (they can conduct electricity as liquids or in the aqueous phase) Next >

15. H+ Cl- OH- Na+ Na+ Cl- H2O acid + base → salt + waterHCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) Salt Formation Salts are typically formed from neutralization reactions between acids and bases. Brønsted-Lowryacid solutions contain hydrogen ions, H+, whereas Brønsted-Lowry basescontain hydroxyl ions, (OH)-. When acids and bases react, the H+ and (OH)- ions immediately combine to form water, while the other components of the solution form a salt. Next >

16. Na+ Cl- H2O Salt Formation Salts can be either soluble or insoluble in a given solvent, depending upon the identity of the solute and the solvent. To obtain a sample of a soluble salt, it is often necessary to evaporate the solvent away leaving the solute as a solid salt residue. In this way, sodium chloride salt can be obtained by evaporating the products of the neutralization reaction between sodium hydroxide and hydrochloric acid. Next >

17. NaOH(aq) → Na+(aq)+ OH-(aq) HCl(aq) → H+(aq)+ Cl-(aq) Na+(aq) + OH-(aq) + H+(aq)+ Cl-(aq) → H2O(l) + Na+(aq) + Cl-(aq) Soluble Salts Sodium chloride (NaCl) is a typical example of a salt which is commonly found in nature. It can be created in the laboratory through the neutralization reaction of sodium hydroxide and hydrochloric acid. Sodium chloride is soluble in aqueous solution, which can be evaporated to leave a pure sample of common salt. Next >

18. Question 4 The name of the salt formed from the reaction of sodium hydroxide and hydrochloric acid is: A) Sodium hydride B) Chloric hydroxide C) Sodium chloride D) Chlorine dihydride Next >

19. Question 4 The name of the salt formed from the reaction of sodium hydroxide and hydrochloric acid is: A) Sodium hydride B) Chloric hydroxide C) Sodium chloride D) Chlorine dihydride Next >

20. AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq) Insoluble Salts Chloride salts, Cl-, are soluble in aqueous solution, whereas salts of other anions may be less soluble. Carbonate salts, (CO3)2-, for example, are insoluble in aqueous solution, unless the cation is a Group 1 metal or ammonium (NH4)+. Other insoluble salts are formed when displacement reactions of two soluble salt solutions take place. Next >

21. Water of Crystallization Water of crystallization is water that forms bonds with metal salts and remains after drying in a fixed proportion to the salt. The water can frequently be removed by heating the salt until it dissociates and evaporates away. It is often replaced by water vapor at room temperature. Copper sulfate pentahydrate, CuSO4·5H2O, can be converted to anhydrous copper sulfate (CuSO4, with no water of crystallization) on heating. Its blue color is then lost. Next >

22. Question 5 Water of crystallization is: A) The amount of water needed to dissolve a crystal of substance B) Water that forms bonds with metal salts and remains after drying in fixed proportions C) Water vapor that associates with a salt after drying Next >

23. Question 5 Water of crystallization is: A) The amount of water needed to dissolve a crystal of substance B) Water that forms bonds with metal salts and remains after drying in fixed proportions C) Water vapor that associates with a salt after drying Next >

24. Salt Identification Salts can be identified by their chemical properties (how they react with other substances) and physical properties (such as melting point and solubility in a range of solvents). Next >

25. Salt Identification The identity of anions is usually established by examining the reactions of the precipitates they form, whereas the identity of cations can be established with flame tests or, often, from the color of the complex ion solution. Next >

26. XCO3(aq) + 2H+(aq) → CO2(g) + H2O(l) + X+(aq) Salt Identification: Anions Some of the most common and important anions in salts can be identified in a series of simple displacement reactions. Carbonate salts, (CO3)2-, are easily identified by reacting the solution with acid. Carbon dioxide is evolved according to the formula: where the CO2 can be detected using limewater, which turns milky when CO2 is bubbled through it. Next >

27. Salt Identification: Anions Sulfate (SO4)2- ions can be identified through the introduction of strontium nitrate or chloride solution. A white precipitate of strontium sulfate will form as the result of a displacement reaction. Next >

28. Salt Identification: Anions Nitrate (NO3)2- ions are more difficult to identify. Among the more common methods are the decolorization of acidified potassium permanganate and the liberation of iodine from acidified potassium iodide solution. Next >

29. Salt Identification: Anions Halide (Cl-, Br-, and I-) ions can readily be identified by forming a precipitate using silver nitrate solution and conducting a visual and solubility analysis of the precipitate formed. Silver chloride Silver bromide Silver iodide Next >

30. Salt Identification: Anions In this case: • chloride ions form a white precipitate completely soluble in dilute ammonia solution Silver chloride • bromide ions form a cream, partially soluble precipitate Silver bromide Silver iodide • iodide ions form a yellow, totally insoluble precipitate Next >

31. Positive flame test for sodium Positive flame test for potassium Salt Identification: Cations When a sample of metal ions is introduced directly to a flame, some of its electrons are promoted to higher energy levels by the heat. Next >

32. Positive flame test for sodium Positive flame test for potassium Salt Identification: Cations As these electrons fall back from one energy level to another, they will emit photons of light. This light is of different colors depending on the difference in energy levels of the element, so this allows the metal cation to be identified. Sodium ions, for instance, emit an orange flame, while those of barium are green. Next >

33. Question 6 What is the common laboratory test for sulfate salts? A) Add strontium nitrate or chloride and check for a white precipitate B) Check for the decolorization of acidified potassium permanganate solution C) Check for the formation of carbon dioxide, which can be checked with lime water D) Add silver nitrate and dissolve the precipitate in ammonia solution Next >

34. Question 6 What is the common laboratory test for sulfate salts? A) Add strontium nitrate or chloride and check for a white precipitate B) Check for the decolorization of acidified potassium permanganate solution C) Check for the formation of carbon dioxide, which can be checked with lime water D) Add silver nitrate and dissolve the precipitate in ammonia solution Next >

35. Electrolysis One of the most important properties of soluble salts is their ability to act as electrolytes in aqueous solution. This means that they are able to conduct electric currents. This happens because of the free movement of ions in the solution. Copper sulfate solution Next >

36. Ethanoate base (CH3COO-) Ethanoic acid (CH3COOH) Buffer Solutions Buffer solutions are solutions, often containing salts, that are able to resist minor changes in pH (concentration of H+ ions). Acidic buffers maintain a pH below 7 and are composed of a weak acid and one of its salts; basic buffers maintain a pH above 7 and are composed of a weak base and its salt. An example of an acidic buffer is a solution of ethanoic (acetic) acid and sodium ethanoate (acetate). Next >

37. Question 7 "Acidic buffers maintain a pH above 7 and are composed of a weak base and one of its salts." Is this statement true or false? Answer True or False. Next >

38. Question 7 "Acidic buffers maintain a pH above 7 and are composed of a weak base and one of its salts." Is this statement true or false? Answer True or False. False Next >

39. Most reactive Potassium Sodium Calcium Magnesium Aluminum Zinc Iron Tin Lead Copper Silver Gold Platinum K Na Ca Mg Al Zn Fe Sn Pb Cu Ag Au Pt Least reactive Metal/Salt Reactions When a metal is added to a salt solution, a reaction may occur if the metal added is more reactive than the metal ion in solution. This is an example of a displacement or substitution reaction. The higher placed metal on the Metal Reactivity Series will displace the other metal and make it form a precipitate. Next >

40. Most reactive Potassium Sodium Calcium Magnesium Aluminum Zinc Iron Tin Lead Copper Silver Gold Platinum K Na Ca Mg Al Zn Fe Sn Pb Cu Ag Au Pt Least reactive CuSO4(aq) + Mg(s) → MgSO4(aq) + Cu(s) Metal/Salt Reactions In the reaction between copper(II) sulfate and magnesium, for example, the less reactive copper will be displaced. Next >

41. Complex Ion Formation One of the most important reactions of transition metal salts is the formation of complex ions in a solution of water or another polar solvent. These often have distinctive and unique colors. When a transition metal ion is placed in water, one of the lone pairs of electrons on a water molecule forms a bond with the metal ions. The compound formed is known as a complex ion, and the water (or other electron donor) is known as a ligand. Next >

42. [M(A)x]y+ Complex Ion Formation The formulae for complex ions are written as follows: where M is the metal ion, A is the ligand, X is the number of ligands bonded to the central metal ion, and Y is the overall charge of the complex. Therefore, in the complex ion [Cu(H2O)6]2+, one copper ion is bonded to six water molecules, and the overall charge on the complex ion is 2+. Next >

43. Ligand Formation Various substances with lone pairs can act as ligands. As they donate electrons, they are Lewis bases and the metal ion receiving electrons is a Lewis acid. Other important ligands include ammonia, NH3, which has one lone electron pair, and chloride ions (Cl-), which can form bonds with one of its four electron pairs. Different ligands of a known metal ion can easily be identified through the color of the solution alone. Next >

44. Question 8 When a transition metal salt reacts with water, an ionic compound is formed. In this compound: A) The transition metal ion is the complex ion and water is the ligand B) Water is the complex ion and the transition metal ion is the ligand C) Water is the ligand and the entire compound is the complex ion D) The transition metal ion is the ligand and the entire compound is the complex ion Next >

45. Question 8 When a transition metal salt reacts with water, an ionic compound is formed. In this compound: A) The transition metal ion is the complex ion and water is the ligand B) Water is the complex ion and the transition metal ion is the ligand C) Water is the ligand and the entire compound is the complex ion D) The transition metal ion is the ligand and the entire compound is the complex ion Next >

46. Question 9 "As transition metal ions receive electrons from another molecule, they act as Lewis acids." Is this statement true or false? Answer True or False. Next >

47. Question 9 "As transition metal ions receive electrons from another molecule, they act as Lewis acids." Is this statement true or false? Answer True or False. True Next >

48. Excess HCl Excess H2O Ligand Substitution Often, a change in the concentration of different electron donors in a solution will result in ligand substitution and the formation of new, differently colored complex ions. For example, when an excess of hydrochloric acid is added to a solution of cobalt(II) ions, chloride ions will replace water molecules as ligands, and the solution will change from pink to blue. This reaction is reversible when more water is added. Next >

49. Complex Ion Colors Some of the more common complex ions of transition metals are as follows: [Cu(H2O)6]2+: blue [CuCl4]2-: yellow/green (excess HCl) [Fe(H2O)6]2+: pale green [Co(H2O)6]2+: pink [CoCl4]2-: blue [Cr(H2O)6]2+: blue [Cr(H2O)6]3+: ruby red Next >

50. Question 10 Cobalt(II) ions form a pink compound when water molecules are its ligands. What color compound do they form when chloride ions are its ligands? A) Blue B) Green C) Yellow D) Red Next >