Chapter 11 part 3: Electrolytes

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Ralph Lindsey
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1 Chapter 11 part 3: Electrolytes Read: BLB 4.1, 4.5; 13.4 HW: BLB 4:3, 15, 37, 61, 71, 72, 73; 13:39, 47 Packet 4:1 3, 13:1-5 Know:! solutions! electrolytes SOLUTIONS Homogeneous mixture: Solute: Solvent: Aqueous solutions: Dr. L. Van Der Sluys Page 1 Chapter 13 part 1 Dr. L. Van Der Sluys Page 2 Chapter 13 part 1 hvordan å signere en autograf

2 Distilled H 2 O Tap H 2 O NaCl(aq) 1M HCl(aq) 1M CH 3 COOH sugar(aq) CH 3 OH Which Bulbs Light Up? Bulb Wattage For bulb to light, some minimum amount of current is needed. amount of current is related to the CONDUCTIVITY of the solution. CONDUCTIVITY: ability to conduct electricity DEFINITION: Electrolytes Strong COMPLETELY ionized(in solution) Good conductors NaCl(s) + H 2 O! Na + (aq) + Cl " (aq) + H 2 O HCl(aq) + H 2 O! H 3 O + (aq) + Cl " (aq) Weak PARTIALLY ionized (in solution) Poor conductors NH 3 (aq) + H 2 O CH 3 COOH(aq)+H 2 O NH 4 + (aq) + OH " (aq) CH 3 COO " (aq)+h 3 O + (aq) Nonelectrolytes NOT ionized in solution Non-conductors C 6 H 12 O 6 (s)+h 2 O! C 6 H 12 O 6 (aq)+ H 2 O glucose Dr. L. Van Der Sluys Page 3 Chapter 13 part 1 Dr. L. Van Der Sluys Page 4 Chapter 13 part 1

3 The Solution Process a) Dissolution of an electrolyte in water produces solvated. Solvation stabilizes the ions and prevents recombination. Example Problem: Based on the results of the demo, which one of the following is a weak electrolyte? a) distilled water Example: NaCl dissociates into ions. b) NaCl(aq) c) 1M HCl(aq) d) 1M CH3COOH(aq) e) sugar(aq) f) CH3OH(aq) b) Dissolution of a non-electrolyte in water produces solvated. Example: CH3OH does not dissociate Dr. L. Van Der Sluys Page 5 Chapter 13 part 1 Dr. L. Van Der Sluys Page 6 Chapter 13 part 1

4 Identifying an electrolyte Ionic compounds: A) Is the compound ionic or molecular? If Ionic: it is a strong electrolyte Note: it could be insoluble If Molecular.... B) If it is molecular, is it an acid or a base? Yes: it is a strong or weak electrolyte No: it is a non-electrolyte. Examples of electrolytes (strong or weak) Acids donate H + (aq) Bases accept H + (aq) Salts formed by replacing one or more H + of an acid with another cation Examples of non-electrolytes: Alcohols Carbohydrates (sugar) Aldehydes, ketones Examples of WEAK electrolytes: Weak Acids (including Carboxylic Acids) Weak Bases (including Amines) Metal + nonmetal (usually) Eg. NaCl K 2 SO 4 Mg(NO 3 ) 2 NH 4 Cl What can you say about the melting points of ionic compounds? Molecular compounds: All nonmetals or nonmetals & metalloids. Eg. HCl H 2 O CH 3 COOH NH 3 What can you say about the melting points of molecular compounds? Dr. L. Van Der Sluys Page 7 Chapter 13 part 1 Dr. L. Van Der Sluys Page 8 Chapter 13 part 1

5 Strong or weak electrolyte? 1) Assume all salts are strong electrolytes. 2) Memorize strong acids and strong bases; all are strong electrolytes. Common misconception: "All Electrolytes are ionic compounds" NOT TRUE! Strong electrolytes ionic or molecular compounds that ionize completely in solution. Weak electrolytes molecular compounds that are partially ionized in solution. Nonelectrolytes molecular compounds that do not ionize in solution If a compound is an acid or a base, but is NOT one of the strong acids or bases, what MUST it be? Dr. L. Van Der Sluys Page 9 Chapter 13 part 1 Dr. L. Van Der Sluys Page 10 Chapter 13 part 1

6 Which one of the following is an ionic compound? A. H 2 O B. NH 4 Cl C. CH 3 COOH D. NH 3 Electrolyte Flowchart molecular Is it an acid? Water soluble Compound ionic Is HCl a molecular or ionic compound? A. molecular B. ionic Which of the following is/are a weak electrolyte(s)? A=WEAK, B=STRONG HBr NH 4 Cl CH 3 CH 2 COOH Is it a strong acid? Yes Strong Electrolyte Yes No Strong electrolyte no weak electrolyte Is it a molecular base? (eg. NH 3 ) yes weak electrolyte no non electrolyte NH 3 Dr. L. Van Der Sluys Page 11 Chapter 13 part 1 Dr. L. Van Der Sluys Page 12 Chapter 13 part 1

7 These are all water soluble compounds. Are they strong, weak or non electrolytes? HCl NaCl CH 3 OH A=WEAK, B=STRONG, C=NON Use the Flowchart on the previous page CH 3 COOH (acetic acid) NH 3 Fe(NO 3 ) 2 Ca(OH) 2 Dr. L. Van Der Sluys Page 13 Chapter 13 part 1

Properties of Solutions (electrolytes) Chapter 4.1. Solution process (energy changes)

Chapter 13 SOLUTIONS Properties of Solutions (electrolytes) Chapter 4.1 Solution process (energy changes) Solubility saturation supersaturation Factors that affect solubility intermolecular interactions