Ch 14- Solutions

Mixtures Mixture: blend of 2 or more kinds of matter, each retaining its own properties Heterogeneous Not uniform in composition Ex) Vegetable Soup, chocolate chip cookies Homogeneous Uniform in composition Salt Water Solutions

Matter Pure substance Element Compound Mixture Homogeneous solutions colloid Heterogeneous

Suspensions Suspension: Particles of a solute are so large that they settle out unless they are mixed or agitated (heterogeneous) Example: Clay in Water, Muddy Water

Colloids Colloids: Particles of intermediate size between solutions and suspensions (heterogenous) Cant see through them Examples:

Used to distinguish between solutions and colloids Tyndall Effect Used to distinguish between solutions and colloids Light is scattered when shone through a colloid

Solution A homogeneous mixture of two or more substances, the composition of which may vary. Examples: - Kool-Aid Salt water Soda

Solutions Solute – the substance that is dissolved Solvent - the substance which dissolves the solute and is normally present in excess In salt water, salt is the solute and water is the solvent

Types of Solutions Gaseous solutions- Two or more gases are mixed. Example: Air (oxygen in nitrogen)

Liquid Solutions Liquid solutions- Solutions which have a liquid solvent and either a gas, liquid or solid as the solute. Aqueous solutions- water is the solvent Solute Solvent Example gas liquid Seltzer liquid liquid antifreeze solid liquid salt water

Types of Solutions Solid solutions- Solutions which have a solid solvent and either a gas, liquid, or solid solute. Solute Solvent Example gas solid charcoal filter liquid solid dental filling solid solid copper in silver

Alloys Alloys are solutions of two or more metals mixed evenly (homogenous) Ex- steel, bronze, brass, sterling silver

Miscible vs. Immiscible A miscible pair of substances can be mixed together in any proportion to form a solution. An immiscible pair of substances cannot be mixed together to form a solution. Example: Oil and water are immiscible.

Solubility Solubility - amount of solute that will dissolve in a given amount of solvent

Concentration Dilute – small amount of solute in the solution Concentrated – large amount of solute in the solution

Factors affecting solubility for solids dissolved in a liquid (sugar water): Temperature – as temp. increases, solubility increases Surface area – increased surface area increases solubility (crush the solid) Stirring – increased stirring increases solubility Pressure – has no effect on solubility

Factors affecting solubility of gases dissolved in a liquid Temperature – as temp. increases, solubility decreases Surface area – has no effect on solubility Stirring – increased stirring decreases solubility Pressure – increased pressure increases solubility

Concentrations Unsaturated- A solution that has less than the maximum amount of solute that can be dissolved. Saturated- A solution that contains as much solute that can be dissolved under existing conditions of temperature and pressure. Supersaturated- A solution that contains more than the maximum solute which can be dissolved.

The process of solvation Water molecules, being polar and in constant motion, knock off and attract ions from any ionic solid. Then they surround the ion and act to prevent it from re-attaching to the ionic crystal.

Solution equilibrium Eventually the water becomes so full of ions that it can no longer prevent some ions from re-attaching to the parent crystal. We call this a saturated solution and the solution is said to be in equilibrium.

https://www.youtube.com/watch?v=EBfGcTA JF4o

Solubility curve diagrams For most solids solubility in a liquid increases as temp increases. For most gases solubility in a liquid decreases as temperature increases.

What is the solubility of Sodium Acetate, CH3CO2Na, at 60 oC? Which substance is least soluble at 20 C? How many grams of potassium bromide can be dissolved in 200ml of water at 60 C? At 20 C, 80g of sodium nitrate is dissolved in 100ml of water. Is this solution unsaturated, saturated, or supersaturated? Is 60 grams of sodium acetate in 50 mL of water at 60 oC saturated, unsaturated, or supersaturated?

A saturated solution of potassium bromide is formed from 100ml of water. If the saturated solution is cooled from 80 C to 40 C, how many grams of precipitate are formed?

You can dissolve gases into water? Sure, fish don’t breath water they breath oxygen just like you and I. Where is the oxygen? It is dissolved in the water. - thermal pollution Consider a can of soda. Open the can and it fizzes from dissolved carbon dioxide leaving solution.

Electrolytes vs Nonelectrolyte Electrolyte = a substance that dissolves in water to give an electrically conducting solution. Ionic solids and acids dissolved in water - ex: salt water Nonelectrolyte = a substance that dissolves in water to give a nonconducting or very poorly conducting solution. Molecular (covalent bond) compounds – ex: sugar water

Dissociation When an ionic compound dissolves in water, the ions separate from each other (cations and anions) Ex: NaCl(s)  Na+(aq) + Cl-(aq) Ex: CaCl2(s) Ca+2(aq) + 2Cl-(aq) Dissociation equations must: Be balanced Show correct ionic charges Show physical states.

Properties of Solutions - + sugar - + acetic acid - + salt Non- Electrolyte Weak Electrolyte Strong Electrolyte solute exists as molecules only solute exists as ions and molecules solute exists as ions only DISSOCIATION IONIZATION View animation online.

Molarity Gives us a numerical value to describe concentration Molarity (M) = moles of solute liters of solution

Molarity Ex. 1 125 ml of solution contains 3.5 moles of solute. What is the molarity of the solution?

Molarity Ex. 2 To make a 4.00 M solution, how many moles of solute will be needed if 12.0 liters of solution are required?

Molarity Ex. 3 What is the molarity of a solution of HNO3 that contains 12.6 grams HNO3 in 1.0 L of solution?