In-Class Problem Solvation of Ionic Compounds What dissolved species are present in a solution of: –KCN –NaClO 4 –K 3 PO 4
Electrolytes vs. Nonelectrolytes Electrolyte: substance that dissociates Nonelectrolyte: substance that 3 types of solutes in aqueous solutions:
Electrolytes as Conductors Aqueous solutions can Depends on number of Transport of ions through solution causes
Molecular Compounds in Water Aqueous solutions of molecular compounds do not –Ex: If no ions in solution, But… some molecular compounds dissociate into ions in aqueous solutions:
Strong Electrolytes: completely dissociate in solution –STRONG acids and bases (considered molecular compounds) Weak Electrolytes: yield small concentration of ions when dissolved and mostly remain in molecular form –Ions exist in –Weak acids and bases Strong and Weak Electrolytes
Concentrations of Solutions Concentration: amount of solute dissolved in a –Change amounts of to change concentration Measures of solution concentration –Molarity: moles of solute per Units: –Molality: moles of solute per Units: mol/kg
In-Class Problem Calculating Molarity Calculate the molarity of a solution made by dissolving 5.00 g of glucose in 100 mL of water.
In-Class Problems Calculating Molar Concentration of Ions What is the molar concentration of K + ions in a 0.015 M solution of potassium chloride? What is the molar concentration of K + ions in a 0.015 M solution of potassium carbonate? Why?
In-Class Problems How many grams of sodium sulfate are there in 15 mL of 0.50 M sodium sulfate? How many mL of 0.50 M sodium sulfate solution are needed to provide 0.038 mol of this salt? What volume of 2.50 M lead (II) nitrate solution contains 0.050 mol of nitrate? What volume of 2.50 M lead (II) nitrate solution contains 1.30 g of Pb 2+ ?
Dilutions A solution of lower concentration is obtained by Key: Number of moles in both concentrated ( ) solution and () solution
In-Class Problems Diluting Solutions How many mL of a 5.0 M K 2 Cr 2 O 7 solution must be diluted to prepare 250 mL of a 0.10 M solution? If 10.0 mL of a 10.0 M stock solution of NaOH is diluted to 250 mL, what is the concentration of the resulting solution?
In-Class Problems Solution Stoichiometry How many grams of sodium hydroxide are needed to neutralize 20.0 mL of a 0.150 M sulfurous acid solution? How many liters of a 0.50 M HCl solution are needed to react completely with 0.100 mol of lead(II) nitrate, forming a precipitate of lead(II) chloride?
Titrations Suppose we know the concentration of a NaOH solution and we want to find the concentration of a HCl solution We know: What do we want? What do we do? –Take a known volume of the
Titrations What do we get? –Volume of –We know molarity of, so we can calculate moles of Next step? –We also know –We can calculate moles of Can we finish? –Knowing moles of and volume of we can calculate
In-Class Problems Acid-Base Titrations What is the molarity of an sodium hydroxide solution if 48.0 mL is needed to neutralize 35.0 mL of 0.144 M carbonic acid? 45.7 ml of 0.500 M sulfuric acid is required to neutralize a 20.0 mL sample of potassium hydroxide solution. What is the concentration of the potassium hydroxide solution?
In-Class Problem Redox Titrations An iron ore is dissolved in acid and the iron is converted to Fe 2+. The sample is then titrated with 47.20 mL of 0.02240 M MnO 4 - solution. The redox reaction that occurs during titration is as follows: MnO 4 - (aq) + 5Fe 2+ (aq) + 8H + (aq) Mn 2+ (aq) + 5Fe 3+ (aq) + 4H 2 O (l) –How many moles of MnO 4 - were added to the solution? –How many moles of Fe 2+ were in the sample? –How many grams of iron were in the sample? –If the sample had a mass of 0.8890 g, what is the percentage of iron in the sample?
Sample Test Question 70.5 mg of potassium phosphate is added to 15.0 mL of 0.050 M silver nitrate solution, resulting in the formation of a precipitate. Write the molecular equation for the reaction. What is the limiting reagent in the reaction? Calculate the theoretical yield, in grams, of the precipitate that forms.