Presentation on theme: "SOLUTIONS Solution – homogeneous mixture made up of very small particles; the size of individual molecules, atoms, or ions Parts of a solution solute-"— Presentation transcript:
1 SOLUTIONSSolution – homogeneous mixture made up of very small particles; the size of individual molecules, atoms, or ionsParts of a solutionsolute- the substance that is considered to be the dissolved substance2. solvent – the substance in which the solute dissolves
2 Aqueous solution (aq) water is the solvent Tincture alcohol is the solvent“like dissolves like” meaning that substances that contain similar bond types will dissolve in each other.Polar solvents will dissolve polar and ionic substances (molecule to ion attraction) but will not dissolve non polar substances (oil and water)
3 Typical properties: 1)solutions are homogeneous mixtures (aq) 2)dissolved particles will not come out of solution no matter how long it stands as long as it is covered to prevent evaporation 3) Clear and transparent- dissolved particles are too small to see. It will not disperse light
4 4) Because of extremely small particle size the solution will pass through the finest filters and leave no residue5)A solution is considered to be a single phase even though the components may be of different phases before the mixture was formed
5 Types of solutions1)gas solutions- gases or vapors dissolve in one anotherExample: Air2)liquid solutions- liquid solvent in which a gas, liquid or solid is dissolvedEx: sugar water , carbonated beverages, antifreeze (ethylene glycol in water)
6 a. Miscible- two liquids that dissolve in one another- must have similar bonding b. Immiscible- two liquids that do not dissolve in one another. Like oil and water must have dissimilar bonding 3)Solid solutions – mixture of solids uniformly spread throughout each other at the atomic or molecular level.
7 EX: alloy –2 or more metals - brass is copper and zinc Amalgam-alloy when one of the metals is Hg- fillings are a Ag-Hg amalgam
8 Solubility- maximum amount of solute that can dissolve in a certain quantity of a solvent at a certain temperatureFactors affecting solubility1. Nature of the solute and solventExample: 1 g of PbCl2 dissolves in 100g of water at room temp200g of ZnCl2 dissolves in 100 g of water at room temp
9 Temperature. Generally solubility increases as temp. increases EXCEPTION: When the solute is a gas Increasing temp decreases solubility and vice versa.
10 3. Pressure For solid and liquid solutes no changes in solubility with changes in pressure, but for gases solubility increases with increasing pressure and vice versa Carbonated beverages are kept under pressure and when you decrease the pressure by opening them they lose the carbonation
11 Saturated – a solution that has dissolved in it all the solute it can normally hold at a given temperature. If any more solute is added it will fall to the bottom Unsaturated- a solution that contains less solute than it can hold at a certain temperature. If more solute is added it will dissolve
12 Supersaturated- Under special conditions, there are some solutions that can actually hold more solute than is present in their saturated solutions at a given temperature.If more solute is added all “extra” solute immediately falls out of solutionExamples sodium acetate NaC2H3O2 and sodium thiosulfate Na2S2O3
13 Molecule-ion attraction a Molecule-ion attraction a. the term molecule refers to a polar solvent while ions refers to an ionic compound b. An ionic compound is placed in liquid ammonia, water or alcohol
14 c. Attraction between the positive and negative ions of the ionic compound and the oppositely charged poles of the solvent molecule. d. This results in a hydrated ion if the solvent is water
16 Preparation of a supersaturated solution 1 Preparation of a supersaturated solution 1. Add more solute to the solvent( usually water) than will dissolve at room temperature 2. Heat the solution until all the solute dissolves, do not boil 3. Gently place the hot solution in an ice bath and allow it to cool undisturbed. 4. Once the solution is cooled to room temperature a supersaturated solution exists.
17 Dilute- amount of solute dissolved is small in relation to the amount of solvent. It is considered a weak solutionConcentrated – amount of solute dissolved is large in relation to the amount of solvent. It is considered a strong solution.
18 Table F- Solubility Guidelines Used to predict if various compounds dissolve in water.
19 Solubility curves1. Graph of amount of solute in 100g of water versus temperature2. TABLE G3. Tells the number of grams that needs to be dissolved in 100g of water at a given temperature to make a SATURATED SOLUTION.
21 Examples:How many grams of KNO3 needs be dissolved to produce a saturated solution in 100g of water at 50C?How many grams of KNO3 needs be dissolved to produce a saturated solution in 50g of water at 50C?How many grams of KNO3 needs be dissolved to produce a saturated solution in 500g of water at 50C?
22 5. Can be used to predict if a solution is saturated, unsaturated or supersaturated. a. saturated solutions fall on the curve b. unsaturated solutions fall below the curve c. supersaturated solutions fall above the curve
23 6. Examples:A solution is prepared by dissolving 80 g of NaNO3 in 100 g of water at 30 C. Is this solution unsaturated, saturated or super saturated?A solution is prepared by dissolving 70g of NH4Cl in 100g of water at 80 C. Is this solution unsaturated, saturated or supersaturated?
24 Concentration1. Definition: amount of solute dissolved in a given amount of solvent2. The higher the value the more concentrated the solution4 Methods for expressing concentrationsMolaritya. number of moles of solute per liter of solution
25 b. Formula found on Table T Molarity = moles of solute Liter of solution Units: M or moles/liters 2. Percent by mass- a. Used when a solid is dissolved in a liquid % by mass = mass of solute x 100 mass of solution
26 3. Percent by volumea. Used when two liquids are mixed to form a solution% by volume = volume of solute x 100volume of solution4. Parts per milliona. Specifies the number of parts of solute in 1 million parts of solution
27 b. Used when the amount of solute is small compared to the amount of solvent. c. Formula on Table T Ppm = mass of solute x 1,000,000 Mass of solution d. units ppm
28 Preparing a solution 1. Calculate the number of grams of solute that must be added using the correct formula from the information given 2. Add this much solute to a volumetric flask of the correct volume. 3. Fill the flask about ¾ of the way with solvent (usually water) 4. Cap the flask and invert to mix. (repeat until all solute is dissolve) 5. Fill the flask to the line with solvent. 6. Invert to finish mixing.
29 Dilutions:M1V1 = M2V2M1 = molarity of original sampleV1 = volume of original sampleM2 = molarity after dilutionV2 = volume of solution after dilution
30 Electrolytes and nonelectrolytes a. -compounds that conduct electricity in solutionb. contain mobile charged particles(ions) in the solution
31 2. Strong electrolyte-electrolytes that form large numbers of ions in solution they cause the bulb of a conductivity apparatus to glow brightly. Examples: Ionic Solids, strong acids and bases
32 3. Weak electrolyte- electrolytes that are poor conductors- they form few ions in solution and cause the bulb of the conductivity apparatus to glow faintly. Examples weak acids and bases such as acetic acid and ammonia
33 4. Nonelectrolytes- non conductors of electricity they do not produce ions when placed in water and the bulb does not light at all Examples: sugars, glycerine Colligative properties 1. Properties of solutions such as vapor pressure, boiling point and freezing points that depend upon the number of particles of solute dissolved in a solution.
34 2. Therefore properties such as vapor pressure, boiling point and freezing point will be most affected if the solute is strong electrolyte and least affected if the solute is a nonelectrolyte.BOTH WILL AFFECT THE PROPERTIES JUST TO DIFFERENT EXTENTS
35 3. Solutes that are strong electrolyte break up into many ions therefore there are more dissolved particles in the solution than for a nonelectrolyte.
36 Boiling Point Elevations and Freezing point depressions 1. When any substance is added to a solvent the boiling point increases and the freezing point decreases. The increase or decrease is greatest if the substance added is ionic (strong electrolyte) and least if the substance is molecular (weak or nonelectrolyte)
37 Which of the following compounds when dissolved in water would lower the freezing point the most and why? C6H12O6 NaCl CH3OH MgCl2 AlCl3