1 Solutions Solution- HOMOGENEOUS mixture of 2 or more substances in a single phase. Solute + Solvent = Solution 2 Parts of a Solution

2 SOLUTE – the part of a solution that is being dissolved (usually the lesser amount) SoluteSolventExample solid Alloys (brass, steel) solidliquidSalt water gassolidAir bubbles in ice cubes liquid “suicides” (mixed drinks) gasliquidSoft drinks gas Air SOLVENT – the part of a solution that dissolves the solute (usually the greater amount)

3 Definitions Solutions can be classified as saturated or unsaturated. 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

4 Definitions SUPERSATURATED 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: 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.

5 Supersaturated Sodium Acetate Supersaturated Sodium Acetate One application of a supersaturated solution is the sodium acetate “heat pack.”One application of a supersaturated solution is the sodium acetate “heat pack.”

6 Concentration of Solute The amount of solute in a solution is given by its concentration The amount of solute in a solution is given by its concentration. Molarity (M) = moles solute liters of solution Not liters of solvent but solution!

7 1.0 L of water was used to make 1.0 L of solution. Notice the water left over.

8 PROBLEM: Dissolve 5.00 g of NiCl 2 6 H 2 O in enough water to make 250 mL of solution. Calculate the Molarity. 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 ] = M

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

10 Learning Check How many grams of NaOH are required to prepare 400. mL of 3.0 M NaOH solution?

11 Solution M = moles of solute Liters of solution M * V = moles 3.0 mol * L = 1.2 mol NaOH 1 L 1.2 mole NaOH x 40.0 g NaOH 1 mole NaOH = 48 g NaOH

12 2 ways to make a Solution Weigh out a solid solute and dissolve in a given quantity of solvent.Weigh out a solid solute and dissolve in a given quantity of solvent. Dilute a concentrated solution to give one that is less concentrated.Dilute a concentrated solution to give one that is less concentrated.

13 Making a Solution from a Solid. 2. Weigh Solid. 3. Fill volumetric flask 1/3- ½ full with distilled water. 4. Transfer solid. (Folding paper may help.) 5. Stir until dissolved. Add more water if necessary. 6.Fill flask with distilled water until bottom of the meniscus touches the etched mark. 1. Do calculations

14 Making a Solution By Dilution If your coffee is too strong, you … Dilute it to the proper concentration! How? Add more solvent. M 1 V 1 = M 2 V 2 (where M = Molarity (concentration) and V = Volume (L of solution) ** IMPORTANT : YOU CAN MAKE A WEAKER SOLUTION FROM A MORE CONCENTRATED SOLUTION BUT NOT A STRONGER SOLUTION FROM A MORE DILUTED SOLUTION!

15 Making a Solution By Dilution Ex: How many mL of 2.5M HCl would be produced from 100mL of 5.0M HCl? Step 1: Inventory –M 1 = –V 1 = –M 2 = –V 2 = Step 2: Solve M 1 V 1 = M 2 V 2 non-numerically –V 2 = (M 1 x V 1 ) / M 2 Step 3: Plug & Chug (put #’s into equation & solve) –V 2 = (5.0M x.1L) / 2.5M –V 2 =.2L or 200mL

16 IONIC COMPOUNDS Compounds in Aqueous Solution Many reactions involve ionic compounds, especially reactions in water — aqueous solutions. KMnO 4 in water KMnO 4(aq) → K + (aq) + MnO 4 - (aq)

17 How do we know ions are present in aqueous solutions? The solutions conduct electricity! They are called ELECTROLYTES Aqueous Solutions

18 It’s Time to Play Everyone’s Favorite Game Show… Electrolyte or Nonelectrolyte! Which substance will conduct the best? a. distilled water b. sugar water c. salt water d. tap water

19 How do we know ions are present in aqueous solutions? The solutions conduct electricity! They are called ELECTROLYTES HCl, MgCl 2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions. Aqueous Solutions

20 Aqueous Solutions Some compounds dissolve in water but do not dissociate or conduct electricity. They are called nonelectrolytes. Examples include: sugarethanol ethylene glycol Examples include: sugarethanol ethylene glycol

21 Electrolytes in the Body  Carry messages to and from the brain as electrical signals  Maintain cellular function with the correct concentrations electrolytes

22 Colligative Properties On 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.

23 Change in Freezing Point The freezing point of a solution is LOWER than that of the pure solvent. FP depression = ∆T FP = K f m Pure water Ethylene glycol/water solution

24 Change in Freezing Point Common Applications of Freezing Point Depression Propylene glycol Ethylene glycol – deadly to small animals

25 Common Applications of Freezing Point Depression Which would you use for the streets of Bloomington 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

26 Change in Boiling Point Common Applications of Boiling Point Elevation

27 Boiling Point Elevation and Freezing Point Depression ∆T = Kmi ∆T = Kmi i = van’t Hoff factor = number of particles produced per formula unit. For covalent compounds, i = 1. For ionic compounds, i = the number of ions present (both + and -) CompoundTheoretical Value of i glycol1 NaCl2 CaCl 2 3

28 ACID-BASE REACTIONS Titrations H 2 C 2 O 4 (aq) + 2 NaOH(aq) ---> acid base acid base Na 2 C 2 O 4 (aq) + 2 H 2 O(liq) Carry out this reaction using a TITRATION. Oxalic acid, H 2 C 2 O 4

29 Setup for titrating an acid with a base

30 TitrationTitration 1. Add solution from the buret. 2. Reagent (base) reacts with compound (acid) in solution in the flask. 3.Indicator shows when exact stoichiometric reaction has occurred. (Acid = Base) This is called NEUTRALIZATION. This is called NEUTRALIZATION.