CHEMISTRY Ch. 13 solutions

Types of mixtures Suspension  A mixture in which particle of a material are more or less evenly dispersed within a liquid or gas  Particles can settle out Colloid  Mixture consisting of tiny particle s that are intermediate in size between those in solutions and suspensions  Particles do not settle out Solution  Homogeneous mixture of a solute dissolved in a solvent  The substance that dissolves=solute  The substance that the solute dissolves into=solvent

Separating mixtures Mixtures can be separated by several different methods:  Decanting, centrifugation, filtration, distillation, evaporation, chromatography

Concentration and molarity Concentration  Amount of a particular substance within a certain solution Parts per million  g solute/1,000,000g solution Molality  Measure of concentration  Moles of solute divided by kg of solvent Molarity  Measure of concentration  Moles of solute divided by liters of solution

Solubility and Polarity Solubility  Ability of a solute to dissolve in a certain solvent Miscible  Able to dissolve in a certain substance Immiscible  Unable to dissolve in a certain substance Polar substances are miscible with other polar substances, nonpolar are miscible with nonpolar substances Nonpolar substances are immiscible with polar substances

Solubility of solid compounds Solids will dissolve more quickly if under the following conditions  Increased surface area (smaller pieces)  Stirring the mixture of solute and solvent  Heat up the mixture Chop it up! Fire it up! Stir it up! Let that solute dissociate son!!!!!

dissociation Separation of a molecule into simpler molecules (ions, atoms, etc.)  Hydration is the dissociation of ions when dissolved in water, it occurs when water molecules surround an ion

saturation Saturated  When a solution can not dissolve any more solute Unsaturated  When a solution still has the ability to saturate more solute Supersaturated  A solution holding more dissolve solute than what is required to reach to reach equilibrium at a given temperature  Typically produced by heating a solution and adding more solute and then carefully cooling (crystals typically form if there is a surface for them to grow on)  The formation of crystals from a supersaturated solution is an exothermic process When I am saturated I get dripping wet

saturation Solubility equilibrium  When dissolution and crystallization of a solute occur at the same rate Henry’s Law  At constant temperature the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas on the surface of the liquid (higher pressure=higher solubility)  This is why pop stays fizzy if the cap is left on and goes flat if the cap is removed

Properties of solutions Conductivity  The ability to conduct an electric current  Solutions that contain charged particles have the ability to conduct electricity (pure water can not, water with things dissolved in it can)  Tap water conducts electricity because it contains electrolytes  Electrolyte  Substance the dissolves in a liquid, breaks into ions which have the ability to conduct an electric current  Nonelectrolyte  Liquid or solid substance which does not allow for the flow of an electric current

Properties of solutions Hydronium ion  H 3 O +, it is an ion consisting of a proton combined with a water molecule  Any substance which has a higher concentration of hydronium ions (H 3 O + ) than hydroxide ions (OH - ) is considered to be an acid

Colligative properties  Property of a system that is dependent on the number of particles in the system and independent of the properties of the substances themselves Freezing point depression  As solute is added the freezing point of the solvent is decreased (why we put salt on ice and ethylene glycol (antifreeze) in radiators) Boiling point elevation  As solute is added the boiling point of a solvent is increased

Surfactants Surfactant  A compound that concentrates in between two immiscible phases Detergent  Surfactant used for cleaning purposes Emulsion  Mixture of two or more immiscible substances where one liquid is dispersed in another

Ch. 14 In a completion reaction products do not spontaneously reform reactants Reversible reactions reform the original reactants  They may reach equilibrium (rate at which formation of products and reactants is equal)  At equilibrium the concentration of reactants and products remains equal  Sometimes complex ions (metal ions or atoms bonded to more than one atom or molecule) form during a reversible reaction that is at equilibrium

Equilibrium constants An expression that shows how the concentrations of reactants and products of a reversible reaction at a certain temperature For the reaction: aA + bB cC + dD use the following formula:

Equilibrium constants Using the following equation, calculate the equilibrium constant. N 2 (g) + 3H 2 (g) 2NH 3 (g) A one-liter vessel contains 1.60 moles NH 3,.800 moles N 2, and 1.20 moles of H 2. What is the equilibrium constant?

Equilibrium constants Reactions with equilibrium constant less than 1 favor reactants Reactions with equilibrium constant of 1 are at equilibrium Reactions with equilibrium constant more than 1 favor products

Determining K eq for Reactions at Chemical Equilibrium 1. Write a balanced chemical equation. 2. Write an equilibrium expression. 2. To write the expression, place the product concentrations in the numerator and the reactant concentrations in the denominator. The concentration of any solid or a pure liquid that takes part in the reaction is left out. For a reaction occurring in aqueous solution, water is omitted. 3. Complete the equilibrium expression 2. Finally, raise each substance’s concentration to the power equal to the substance’s coefficient in the balanced chemical equation.

Determining K eq for Reactions at Chemical Equilibrium Sample Problem A An aqueous solution of carbonic acid reacts to reach equilibrium as described below. The solution contains the following solution concentrations: carbonic acid, 3.3 × 10 −2 mol/L; bicarbonate ion, 1.19 × 10 −4 mol/L; and hydronium ion, 1.19 × 10 −4 mol/L. Determine the K eq.

The Solubility Product Constant, K sp Equilibrium constants for the dissolution of slightly soluble salts are called solubility product constants, K sp, and have no units. The K sp for calcium fluoride at 25°C is 1.6  10 −10. K sp = [Ca 2+ ][F − ] 2 = 1.6  10 −10

Solubility constants Equilibrium constants for the dissolution of slightly soluble salts are called solubility product constants, K sp, and have no units.

Determining K sp for Reactions at Chemical Equilibrium 1. Write a balanced chemical equation. Solubility product is only for salts that have low solubility. Soluble salts do not have K sp values. Equations are always written so that the solid salt is the reactant and the ions are products. 2. Write a solubility product expression. Write the product of the ion concentrations. Concentrations of solids or liquids are omitted. 3. Complete the solubility product expression. Raise each concentration to a power equal to the substance’s coefficient in the balanced chemical equation.

Common ion effect When a solute forms ions that are the same as ions that have already been formed in a solution from another solute one of the solutes will form a precipitate

Copper(I) chloride has a solubility product constant of 1.2 × 10 −6 and dissolves according to the equation below. Calculate the solubility of this salt in ocean water in which the [Cl − ] = 0.55.

Le chatliers principle Le Châtelier’s principle  states that when a system at equilibrium is disturbed, the system ad  Stress is another word for something that causes a change in a system at equilibrium justs in a way to reduce the change  Ex. changes in the concentrations of reactants or products changes in temperature changes in pressure

The equilibrium below occurs in a bottle of soda. After you uncap the bottle, the dissolved carbon dioxide leaves the solution and enters the air. The forward reaction rate of this system will increase to produce more CO 2. This increase in the rate of the forward reaction decreases the concentration of H 3 O +. As a result, the drink gets “flat.”

If ammonia is added, the system responds by forming more product and the solution becomes blue-purple.