2. Solutions

3. I. Solution: Definition A solution is a HOMOGENEOUS mixture of 2 or more substances in a single phase.A solution is a HOMOGENEOUS mixture of 2 or more substances in a single phase. One constituent is usually regarded as the SOLVENT and the others as SOLUTES.One constituent is usually regarded as the SOLVENT and the others as SOLUTES.

4. SOLUTE – the part of a solution that is being dissolved (usually the lesser amount) SOLVENT – the part of a solution that dissolves the solute (usually the greater amount) Solute + Solvent = Solution SoluteSolventExample solid Alloys (brass, steel) solidliquidSalt water gassolidAir bubbles in ice cubes liquid mixed drinks gasliquidSoft drinks gas Air II. Solutions : Components

5. III. Compounds in Aqueous Solution Reactions that involve the use of water as a solvent result in the production of aqueous solutions. Reactions that involve the use of water as a solvent result in the production of aqueous solutions. KMnO 4 in water K + (aq) + MnO 4 - (aq)

6. Solutions that contain acids, bases, and salts as solutes are considered to be electrolytic solutions.Solutions that contain acids, bases, and salts as solutes are considered to be electrolytic solutions. These solutions conduct electricity.These solutions conduct electricity. These solutes are called ELECTROLYTES.These solutes are called ELECTROLYTES. HCl (acid), NaOH (base), and MgCl 2 (salt) are strong electrolytes. They dissociate completely (or nearly so) into ions.HCl (acid), NaOH (base), and MgCl 2 (salt) are strong electrolytes. They dissociate completely (or nearly so) into ions. a) Types of Aqueous Solutions

7. Some compounds dissolve in water but do not conduct electricity. They are called nonelectrolytes.Some compounds dissolve in water but do not conduct electricity. They are called nonelectrolytes. These solutes are usually covalent compounds. These solutes are usually covalent compounds. Examples include: sugarsugar ethanolethanol ethylene glycolethylene glycol Examples include: sugarsugar ethanolethanol ethylene glycolethylene glycol

8. IV. Solutions: Concentration (Qualitative) Solutions can be classified as saturated or unsaturated.Solutions can be classified as saturated or unsaturated. A saturated solution contains the maximum quantity of solute that dissolves at that temperature.A saturated solution contains the maximum quantity of solute that dissolves at that temperature. An unsaturated solution contains less than the maximum amount of solute that can dissolve at a particular temperatureAn unsaturated solution contains less than the maximum amount of solute that can dissolve at a particular temperature

9. SUPERSATURATED SOLUTIONS contain more solute than is possible to be dissolvedSUPERSATURATED SOLUTIONS contain more solute than is possible to be dissolved Supersaturated solutions are unstable. The supersaturation is only temporary, and usually accomplished in one of two ways:Supersaturated solutions are unstable. The supersaturation is only temporary, and usually accomplished in one of two ways: 1.Warm the solvent so that it will dissolve more, then cool the solution 2.Evaporate some of the solvent carefully so that the solute does not solidify and come out of solution.

10. a) Parts per million: Same formula as percent by mass except you need to multiply by one million (not one hundred). Used to describe the concentration of solutions in which the solute is in minute amounts. ppm = grams solute grams solution X 1,000,000 V. Solutions: Concentration (Quantitative) The amount of solute in a solution is given by its concentration The amount of solute in a solution is given by its concentration.

11. Molarity (M) = moles solute liters of solution b)

12. Step 1: Calculate moles of NiCl 2 6H 2 O Step 2: Calculate Molarity NiCl 2 6 H 2 O [NiCl 2 6 H 2 O ] = 0.0841 M PROBLEM: Dissolve 5.00 g of NiCl 2 6 H 2 O in enough water to make 250 mL of solution. Calculate the Molarity.

13. Step 1: Change mL to L. 250 mL * 1L/1000mL = 0.250 L Step 2: Calculate. Moles = (0.0500 mol/L) (0.250 L) = 0.0125 moles Step 3: Convert moles to grams. (0.0125 mol)(90.00 g/mol) = 1.13 g USING MOLARITY moles = MV What mass of oxalic acid, H 2 C 2 O 4, is required to make 250. mL of a 0.0500 M solution?

14. Learning Check How many grams of NaOH are required to prepare 400. mL of 3.0 M NaOH solution? 1)12 g 2)48 g 3) 300 g

15. An IDEAL SOLUTION is one where the properties depend only on the concentration of solute.An IDEAL SOLUTION is one where the properties depend only on the concentration of solute. Need conc. units to tell us the number of solute particles per solvent particle.Need conc. units to tell us the number of solute particles per solvent particle. The unit “molarity” does not do this!The unit “molarity” does not do this! Concentration Units

16. Two Other Concentration Units grams solute grams solution b) MOLALITY (m) % by mass = c) PERCENT BY MASS

17. Learning Check A solution contains 15 g Na 2 CO 3 and 235 g of H 2 O. What is the mass % of the solution? 1) 15% Na 2 CO 3 2) 6.4% Na 2 CO 3 3) 6.0% Na 2 CO 3

18. Using mass % How many grams of NaCl are needed to prepare 250 g of a 10.0% (by mass) NaCl solution?

19. VI. Colligative Properties Key Idea: By adding a solute to a solvent, the properties of the solvent are modified. Vapor pressure decreasesVapor pressure decreases Melting point decreasesMelting point decreases Boiling point increasesBoiling point increases Osmosis is possible (osmotic pressure)Osmosis is possible (osmotic pressure) These changes are called COLLIGATIVE PROPERTIES. They depend only on the NUMBER of solute particles relative to solvent particles, not on the KIND of solute particles.

20. Change in Freezing Point The freezing point of a solution is LOWER than that of the pure solvent. Pure water Ethylene glycol/water solution

21. Common Applications of Freezing Point Depression Which would you use for the streets of Floral Park to lower the freezing point of ice and why? Would the temperature make any difference in your decision? a)sand, SiO 2 b)Rock salt, NaCl c)Ice Melt, CaCl 2 Change in Freezing Point

22. Change in Boiling Point Common Applications of Boiling Point Elevation

23. Solubility Rules: Most covalent compounds are insoluble in water (exceptions include organic acids, bases, and certain low molecular weight alcohols). Most ionic compounds (salts), acids, and bases are soluble in water. There are some exceptions REFERENCE TABLE F Question: Are the following compounds soluble or insoluble in water??? a)Silver nitrate b)Lead iodide c)Magnesium carbonate d)Lithium phosphate SOLUBLE INSOLUBLE

24. NONE

28. Degree of Saturation REFERENCE TABLE G A saturated solution contains the maximum quantity of solute that dissolves at that temperature. An unsaturated solution contains less than the maximum amount of solute that can dissolve at a particular temperature SUPERSATURATED SOLUTIONS contain more solute than is possible to be dissolved As temperature increases, the solubility of a solid solute in a liquid solvent increases. As temperature increases, the solubility of a gaseous solute in a liquid solvent decreases.

29. Question: Unsaturated, Saturated, or Supersaturated??? o C a)105 grams of NaNO 3 in 100 grams of water at 40 o C o C b)105 grams of NaNO 3 in 200 grams of water at 40 o C o C c)40 grams of KCl in 100 grams of water at 60 o C d)From question c, how many more grams of solute can be added until precipitation occurs??? HINT: After plotting a point……..if the point is below the line it is an unsaturated solution, if the point is on the line it is a saturated solution, if the point is above the line either it is a supersaturated solution or an undissolved precipitate exists at the bottom of the solution.