Chapter 12 Solutions

Review Types of mixtures: Heterogeneous mixtures: do not have a uniform composition Homogeneous mixtures: have a uniform composition, solute particles are too small to be seen.  A homogeneous mixture is a solution.

Terms Soluble: capable of being dissolved Solution: a homogeneous mixture of two or more substances in a single phase Solute: the substance that is dissolved, usually the lesser quantity Solvent: the dissolving medium, usually the greater quantitiy Water is the universal solvent

Types of Solutions Solid in liquid: sugar in water Solid in solid: metal alloys; 14-karat gold is a mixture of pure gold with silver and copper to make it more durable Gas in liquid: CO 2 in water = carbonation, NH 3 in water = cleaning solution Liquid in liquid: alcohol in water

Examples of Solutions SoluteSolventExample Gas Gas Air Gas Liquid Soda Liquid Liquid Antifreeze Solid Liquid Ocean Gas Solid Charcoal Filter Liquid Solid Dental Fillings Solid Solid Sterling Silver 12-3

Types of Mixtures: THINK PARTICLE SIZE!!! Solutions: solute particles too small to be seen (Water and Salt, Water and Sugar) Colloids: solute particles intermediate in size – they remain suspended throughout the solvent. (Water and Milk, Water and Mayo) Suspensions: solute particles are so large they settle out upon standing. (Water and Chalk, Water and Sand)

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Types of Mixtures: THINK PARTICLE SIZE!!! The Tyndall Effect: Is it a true solution or a colloid???  The particles in a colloid will scatter light  A true solution will transmit light

Electrolytes & Nonelectrolytes Electrolyte: a substance that dissolves in water to give a solution that conducts an electric current. THE SOLID IONIZES (BECOME CHARGED IONS)

Electrolytes & Nonelectrolytes Nonelectrolyte: a substance that dissolves in water to give a solution that does not conduct electricity. THE SOLID DOES NOT IONIZE (BECOME CHARGED IONS)

SO How do they Ionize? The solution process When the solute is an ionic solid and the solvent is water, solute particles are attracted to the charged ends of the POLAR water molecules. The water molecules pull the ions away from the crystal surface and into solution.

The Solution Process The polar ends of the water molecules are attracted to the charged ions of the solute particles: Na +1 & Cl -1

Factors of Solubility For every combination of solute and solvent, there is a limit to the amount of solute that can be dissolved. Factors: Nature of solute and solvent: are they ionic, polar covalent or nonpolar covalent?! The temperature

The solution process (SOLIDS) To increase the rate of dissolution of the solid solute: crush to increase Surface Area stir to disperse heat to increase movement  All bring solute & solvent in contact with each other

Solution Equilibrium Defined:  The physical state in which the opposing processes of dissolution and crystallization of a solute occur at equal rates. Eventually, solution equilibrium is reached:  solute particles dissolve & return to the crystal at equal rates.  Ex: CaF 2 (s) ⟷ Ca +2 (aq) + 2 F -1 (aq)

Solubility Solutions can be: Unsaturated: contains less than max. amt. of solute possible at that temp. Saturated: contains max. amt. of solute possible at that temp. Supersaturated: contains more than max. amt. of solute possible at that temp.

Supersaturated Solutions If solution is saturated, additional solute will settle to the bottom Heat and stir and more solute is forced to enter the solution Solute remains dissolved even after solution cools down but will re-crystalize easily

Solubility Curve

Practice Using the Solubility Curve What is the solubility of NH3 at 50°C? What is the solubility of KCl at 50°C? What is the solubility of KNO3 at 50°C?

The Solubility Rule “Like Dissolves Like” -Polar dissolves polar and ionic. - Nonpolar dissolves nonpolar.

“Like Dissolves Like” Liquids that are not soluble in each other are immiscible. Ex: oil (non-polar) & water (polar) Liquids that dissolve freely in each other are miscible. Ex: gasoline & grease (both non-polar)

Concentration of Solutions Molarity: the number of moles of solute in one liter of solution. Molarity (M) = amount of solute (mol) volume of solution (L)

Concentration of Solutions

Molarity Problems What is the molarity of a solution that contains moles of H 2 SO 4 in 2.50 L of solution? What is the molarity of a solution prepared by dissolving 25.0 g of HCl (g) in enough water to make mL of solution?water

Molarity Problems Given: 90.0 g NaCl, 3.50L of solution, find Molarity Given: 5.85g of KI, 0.125L of solution, find Molarity

Molarity Problems Given: 0.8L of 0.5M HCl, find moles of HCl How many grams of sulfuric acid are in 0.500L of 0.150M solution?

Molarity Problems If a reaction requires 146.3g of NaCl, what volume of 3.00M NaCl should be used? How many grams of NaCl would you need to prepare 500. mL of a 2.00 M solution?

Molarity Problems A reaction requires 23.4g of K2CrO4. I have a 6.0M stock solution. How much of it should I use for the reaction? How many mL of 0.54 M AgNO3 would contain 0.34g of the solute?

Concentration of Solutions Molality: the number of moles of solute per kilogram of solvent. molality (m) = amount of solute (mol) mass of solvent (kg)

Molality Problems Given: 17.1g sugar, C 12 H 22 O 11 dissolved in 125g water, find the molality

Molality Problems Given: 225g acetone, (CH 3 ) 2 CO, dissolved in 200.g water, find the molality

Molality Problems Given: m solution of iodine, I 2, dissolved in 100.0g of carbon tetrachloride Find mass of solute

Molality Problems How many grams of the solute methanol, CH3OH, are required to prepare a m solution in 400.g of water?

Molality Problems How many grams of the solute HNO3, nitric acid, are required to prepare a 1.00 m solution in 2.00 kg of water?

Review 1.As temperature increases, the solubility of gases in liquids __________________ 2.The substance dissolved is called the ____________ 3.A mixture whose particles separate is a __________ 4.A mixture with particles too small to see is a_______ 5.A mixture that scatters light is a________________ and exhibits the _______________ effect. 6.A substance that d0es not dissolve in a polar solvent is probably __________________ 7.To carry an electric current a solution must contain __________________

Review 8.Liquid solutes and solvents that are not soluble in each other are __________________ and examples include…. 9.A __________________ is a solution whose solute and solvent are both solid metals. 10.The solubility of an ionic compound such as CuCl2 would __________________ with increasing temp. 11.A solution that contains the max. amount of dissolved solute is __________________ 12.A solute molecule that is surrounded by solvent molecules is __________________ 13.Name three alloys:

ANSWERS 1.Decrease 2.Solute 3.Suspension 4.solution 5.Colloid, Tyndall 6.nonpolar 7.ions 8.immiscible 9.alloy 10.Increase 11.Saturated 12.solvated