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Ch. 8 - Solutions, Acids & Bases

Solution = a homogeneous mixture of 2 or more substances

Solute substance whose particles aredissolved in a solution

Solvent substance in which the solutedissolves in

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Solutes/solvents can be liquids, solids &/or gases

Air = gases dissolved in gases

Kool-aid = solids dissolved in water

Solid-Solid solutions particularly of metals are sometimes called ALLOYS

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3 ways things can dissolve in water:

1. Dissociation of ionic compounds = an ionic compound is placed in a solution the solution exerts a greater pull on the ions than the attraction that exists between the ions ions are pulled apart or dissociated is a physical change

Whenanioniccompounddissolvesinwater,thechargedendsofwatermoleculessurroundtheoppositelychargedions.

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2. Dispersion of molecular compounds covalent polar molecules are attracted to polar solvent molecules when enough water (solvent) molecules surround the crystal structure, the waters pull due to its polarity is greater than the pull of the covalent crystal structure and the molecules are pulled away from the crystal and become evenly dispersed throughout the solvent is a physical change

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3. Ionization of molecular compounds process in which neutral molecules gain or lose electrons is a chemical change because 2 new ionic substances are formed.

H2O + HCl H3O+1 + Cl-1

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Physical properties of solutions are often different than those of the solute/solvent alone.

For example: 1. Conductivity = is greater for an ionic solution than for the solid ionic compound 2. Freezing point = mixing two substances such as salt and water, will lower the freezing point of water because the formation of solvent ice crystals is disrupted by the solute

3. Boiling point = can be changed by combining solutes and solvents

Thepresenceofsoluteparticlesaffectshowasolventfreezes.APurewaterfreezesinahexagonalpattern.BInwatersaltedwithMgCl2,thedissociatedMg2+andClionsdisrupttheformationoficecrystals.

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During the formation of a solution, energy is either released (exothermic) or absorbed (endothermic).

Heat of solution = difference between energy required to break bonds between solute particles and the bonds between solvent particles vs. the energy formed when solutes/solvent particles are attracted to each other

EX: Cold packs consist of 2 bags - one with ammonium nitrate and the other with water. The energy required to combine water and the ammonium nitrate is greater than that given off when the ammonium nitrate is broken apart (a positive heat of solution). Heat is pulled from the water and result is a cold pack!

Hot packs use substances with a negative heat of solution (breaking of the solute bonds creates more energy than is required to dissolve in water so heat is given off.)

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Factors that affect the rate of dissolving do so by affecting the collision rate of solute & solvent particles.

They include:

1. Surface area increase surface area = increase in dissolving rate

2. Stirring increased stirring =

increased rate of collision and therefore, increased dissolving rate

3. Temperature increased temperature = more

molecular motion = increased rate of collision between solute and solvent particles = increased dissolving rate

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8.2 - Solubility & Concentration

Solubility = the maximum amount of a solute that dissolves in a given amount of solvent (usually expressed as grams of solute per 100 grams of solvent at a certain temperature)

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Solution solubility is classified as: 1. Saturated solution = contains as much solute as the solvent can hold at a given temperature if you add more solute, it wont dissolve

2. Unsaturated solution = contains less than the maximum amount of solute than can be dissolved you can add more solute & it will dissolve

3. Supersaturated solution = contains more solute than it should be able to hold is a very unstable solution created by heating a solution, dissolving more solute in it & then slowly cooling it.

Inthephotosequence,asinglecrystalofsodiumacetate,NaC2H3O2,isaddedtoasupersaturatedsolutionofsodiumacetateinwater.Theexcesssoluterapidlycrystallizesoutofthesolution.

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Factors that can affect solubility:

1. Polarity of the solvent = likes dissolve likes polar solvents dissolve polar solutes better than if they were of different polarities

2. Temperature = for solids being dissolved in a liquid, solubility will increase as the temperature is increased gases are the opposite - increasing temperature decreases the solubility of a gas in a liquid

3. Pressure = Increasing pressure on a gas in a liquid solution increases its solubility

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Concentration of a solution = amount of solute dissolved in a specified amount of solution

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SOLUBILITYCURVEFORVARIOUSSALTS

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SolubilityforGases

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Section 8.3 - Acids & Bases

Acid = a compound that produced hydronium ions (H3O+) when dissolved in water is considered a proton donor

HCl + H2O --> H3O+ + Cl-

Properties of Acids:1. Sour taste

Ex: citric acid in food2. Reactive with metals

Ex: foil over spaghetti sauce3. Produce color changes in indicators

Ex: Litmus paper (an indicator changes color when exposed to acids/bases) --> blue paper turns red in acid

Common acids:Acetic acid (CH3COOH) = vinegarcarbonic acid (H2CO3)= carbonated beverageshydrochloric acid (HCl)= stomach acidsulfuric acid (H2SO4) = car batteries

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Usesofacids

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Base = compound that produces hydroxide ions (OH-) when dissolved in water considered a proton acceptor

NaOH --> Na+ + OH-

Properties of Bases:1. Bitter taste

Ex: Cacao beans contain the base theobromine, which makes chocolate bitter

2. Slippery feelEx: Soap, cleaning products

3. Color changes in indicatorEx: Bases turn red litmus paper bluephenolphthalein turns magenta in the presence of a baseEx: Hydrangeas color depends on the acidity of the soil (purple if acidic, pink if soil is basic)

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Common Bases:Aluminum hydroxide (Al(OH)3) = deodorantcalcium hydroxide (Ca(OH)2) = concreteMagnesium hydroxide (Mg(OH)2) = antacidSodium hydroxide (NaOH) = drain cleaner

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Sodiumbicarbonate,orbakingsoda,isoftenaddedtoswimmingpoolstoregulatetheacidityofthewater.

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Neutralization = reaction between an acid and a base where the negative ions in an acid combine with the positive ions in a base to produce an ionic compound called a salt and water.

NaOH + HCl --> NaCl + H2O

Common salts:Sodium chloride (NaCl)Sodium carbonate (Na2CO3)Potassium chloride (KCl)Magnesium chloride (MgCl2)

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pH scale --> 0-14 measure of the concentration of hydronium ions in a solution equals -log (H3O+ concentration)

Acids --> pH of less than 7Neutral solution --> pH = 7Bases --> pH greater than 7

The lower the pH value, the greater the H30+ ion concentration. (high pH = low H30+ concentration)

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Strong acids = when placed in water, they ionize almost completely

Ex: HCl, H2SO4, HNO3

Strong bases = when placed in water, they completely dissociate

Ex: NaOH, Ca(OH)2, KOH

Weak acids/weak bases ionize or dissociate only slightly in water.

Buffer solutions = prepared by mixing weak acid or base with its salt buffers are solutions that are resistant to large changes in pH

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Buffer solutions = prepared by mixing weak acid or base with its salt buffers are solutions that are resistant to large changes in pH

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Electrolyte --> a substance that ionizes or dissociates into ions when dissolved in water (salts, strong acids and strong bases are all examples of electrolytes) electrolytic solutions are good conductors of electricity

Batteries & fuel cells use electrolytic solutions

Attachments

coldpacks.pdf

Acidsvs.BasesComparison.notebook

Solutions, Acids, and Bases 1

Using a cold packA cold pack removesheat from the inflammationaround an injury. It also decreasesthe size of capillaries (small bloodvessels) in the injured area, whichreduces swelling and bruising.

Cold PacksInstant hot and cold packs are often used by athletes totreat injuries. Hot packs are also used in cold weatherto warm hands and feet. Both types of pack workthrough the action of chemicals that either release orabsorb heat when they dissolve in water. One type ofcold pack is shown below. Inferring How does shakingthe pack after squeezing it affect the rate of dissolving?

Inside the pack A cold pack consistsof two sealed bags, one inside the

other. The strong outer bag contains solidammonium nitrate powder. The thin-walled inner bag contains water.

Squeezing the pack Whenthe pack is squeezed, the

inner bag containing the waterbursts. The water rushes into theouter bag where it dissolves theammonium nitrate.

Outer bag

Heat absorbed As theammonium nitrate dissolves,

it absorbs energy from the water.This causes the temperature ofthe solution in the bag to droprapidly. The pack is then readyfor use.

Heat absorbed

Ammoniumnitrate powder

Water ininner bag

Ammonium nitratedissolves in water.

Inner bagbursts.

Solutions, Acids, and Bases 1

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Aug 12-11:12 AM AcidsBasesph below 7.0pH above 7.0Tastes sourTastes bitterVinegarBaking sodaReact w/metalsDranoTurns litmus redTurns litmus blueForms H+ ionsForms OH- ions010101010101false

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SMART Notebook

Page 1: Aug 12-4:12 PMPage 2: Aug 12-4:12 PMPage 3: Aug 12-4:12 PMPage 4: Aug 12-4:12 PMPage 5: Aug 12-4:13 PMPage 6: Aug 12-4:14 PMPage 7: Aug 12-4:14 PMPage 8: Aug 12-5:25 PMPage 9: Aug 12-4:14 PMPage 10: Aug 12-4:15 PMPage 11: Aug 12-4:16 PMPage 12: Aug 12-4:16 PMPage 13: Jan 2-2:01 PMPage 14: Aug 12-4:16 PMPage 15: Aug 12-5:55 PMPage 16: Aug 12-4:17 PMPage 17: Uses of AcidsPage 18: Aug 12-4:29 PMPage 19: Aug 12-7:07 PMPage 20: Aug 12-7:08 PMPage 21: Aug 12-5:59 PMPage 22: Aug 12-4:30 PMPage 23: Aug 12-4:30 PMPage 24: Aug 12-4:31 PMPage 25: Aug 12-7:17 PMPage 26: Aug 12-6:05 PMPage 27: Aug 12-4:31 PMAttachments Page 1