A special solution Acids and bases are ALWAYS in a water solution Your body has water in it so they are always dangerous to living things Bases are just as dangerous as acids In low concentrations ID: 1032677
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1. Acids and BasesChapter 16
2. A special solutionAcids and bases are ALWAYS in a water solution.Your body has water in it so they are always dangerous to living things.Bases are just as dangerous as acids.In low concentrations they are not that dangerous and found all over your house.
3. Acids and BasesAciReless than 7sourmetals and bases ase luemore than 7bitter and feel slipperyoils and acidsAlthough they can be dangerous, acids and bases do not react with or “eat”everything.Neither has an effect on glass for example.turn litmus paperhave a pHtastereact withDB
4. Common places to find acids and basesAcidsVinegar- acetic acidcitrus fruits- citric acidcarbonated drinks- carbonic acidYour stomach- hydrochloric acidBasesAntacid tablets (calcium hydroxide)Windex- ammoniaOven cleaner- sodium hydroxideDraino – sodium hydroxide
5. HomeworkUsing the litmus paper provided in class check to see if two common items found in your house are acidic or basic.Report your findings on a piece of paper, and staple the litmus paper with it.You need to report what the items are and if they are acidic or basic.Please exercise caution and common sense. Do NOT test anything dangerous!
6. DefinitionsAcid- a proton (H+) donor [force feeder]Acids produce H3O+ (hydronium) in waterBase- a proton (H+) acceptor [thief]Bases produce OH- (hydroxide) in water
7. Heat of solutionNormally dissolving a substance is an exothermic process.You are normally increasing the state of entropy (measure of disorder)Which normally means you will release heat.There are exceptions, dissolving ammonium nitrate is an endothermic process
8. Always do what you oughta …Always add acid to waterDissolving the acid in water releases heatIf you have a lot of acid and a little water on top, the water typically boils quickly causing the hot acid to spray out.A lot of water on the bottom typically doesn’t boil if the acid is added slowly enough.
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10. Acid Nomenclature ReviewNo Oxygenw/Oxygen An easy way to remember which goes with which…“In the cafeteria, you ATE something ICky”
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12. HBr (aq)H2CO3H2SO3 hydrobromic acid carbonic acid sulfurous acidAcid Nomenclature Review
13. Name Them: HI (aq)HCl (aq)H2SO3HNO3HClO2
14. Self dissociation of water.Some water will dissociate itself H2O +H2O H3O+ +OH-in “pure” water you will findH3O+ has concentration of 1 x 10-7 MOH- has concentration of 1 x 10-7 MThe product of the conc. of H3O+ and OH- is always 1 x 10-14 [ ]-conc. [H3O+] [OH-] = 1 x 10-14
15. pHIn any solution the H3O+ and OH- concentration is always very small.pH- method of representing the H3O+ concentration in a solution.pH = -log [H3O+] So the pH of water is…pH = - log 1 x10-7pH = 7
16. What is a loglog stands for logarithm ~we can use them to solve for an exponent.log xy = y log xFor example log 1 x10-7 =-7the log key on your calculator is log10 meaning it will cancel out a 10^.To reverse a log10 raise the whole thing to the 10th power (10^), this is an antilogThe reversed pH equation is[H3O+] = 10^(-pH)
17. pH valuespH of 7 is neutral- equal [H3O+] and [OH-] below 7 is acidic, higher [H3O+] than [OH-] above 7 is basic or alkaline, higher [OH-] than [H3O+]
18. Acid Base Equations[H3O+] [OH-] = 1 x 10-14pH = -log [H3O+] [H3O+] = 10^(-pH)
19. Sig Figs and pHThe number of decimal places in the log value, pH value, is equal to the number of significant figures in the number that we took the logarithm of, concentration.So [H3O+] = 2.45 x10-4 M 3 sig figspH = -log 2.45 x10-4 M = 3.611 3 decimal places
20. Reversing thatHaving a pH of 4.32 (2 decimal places) gives you a hydronium concentration of…[H3O+] = 10^(-4.32) = 4.8 x10-5 M (2 sig figs)
21. pH problemsWhat is the pH of a 2.4 x 10-4 M H3O+?pH = - log 2.4 x 10-4 pH = 3.62What is the OH- concentration?[H3O+] [OH-] = 1 x 10-142.4 x10-4 [OH-] = 1 x 10-14[OH-] = 4.2 x10-11 M
22. Backwards problemWhat is the [H3O+] and [OH-] of a solution with a pH of 8.75?[H3O+] = 10^(-pH)[H3O+] = 10-8.75 [H3O+] = 1.8 x 10-9 M1.78…x10-9 [OH-] = 1 x 10-14[OH-] = 5.6 x 10-6 M
23. Last oneWhat is the pH and [H3O+] of a solution with a [OH-] conc. of 2.9 x10-4 M?
24. HomeworkWhat is the pH and [H3O+] of a solution with a [OH-] of 5.92 x10-5 M?
25. Neutralization of an acid or base.
26. Mixing acids and bases~creates waterH3O+ + OH- 2 H2O this is called neutralizing the solutiona neutralized solution is no longer dangerous.The point where neutralization is complete is called the equivalence point
27. Salts~the byproduct of an acid and a base.NaOH + HCl H2O + NaCl(base) (acid) (water) (salt)there are several more than just table salt.HNO3 + NH4OH H2O + NH4NO3Acid Base water salt
28. Gases can be createdthis depends on the reactants (not all will)sodium bicarbonate (baking soda) will pretty much always release a gasNaHCO3 + H2SO4 H2O + NaHSO4 + CO2GasSalt
29. Titration~mixing an acid and base perfectly to make a neutral solution.You normally need some kind of indicator for this.Phenolphthalein- when in solution turns red if basic and is clear if acidic.You can also use a pH probe
30. Graph of titrationVolume strong base addedpHequivalence point
31. Using mathTo neutralize a solution you will need to add an equal amount of H3O+ / OH- to what was already present.so thatmol H3O+ = mol OH-This is used if and only if you are at the equivalence point (completely neutral solution)!
32. ProblemIf 94 mL of 4.0 M NaOH neutralizes 6.0 L of an unknown strong acid, what was the H3O+concentration of the unknown? 4 M NaOH x .094 L = .376 mol NaOH.376 mol H3O+/ 6.0 L = .063 M H3O+
33. Another problemIf 127 mL of 2.0 M NaOH neutralizes 4.1 L of an unknown acid, what is the initial concentration of the acid?2.0M(.127 L) = .254 mol NaOH=.254 mol OH- = .254 mol H3O+ 4.1 L=.062 M
34. EquilibriumChapter 17
35. Rates of reactionDifferent reactions happen at different speeds.There are ways to speed up or slow down a reaction.Changing the surface area of the reactantsPowders react more quickly than “chunks”Changing the amount/concentration of reactantsMore reactant speeds up the reactionChanging the temperatureWarmer reactions tend to go fasterAmount of rate change depends on the reaction.
36. Catalysts and InhibitorsCatalyst- something that increases the rate of a reaction without changing the products of the reaction.Catalytic converter speeding the reaction of emissions of a car to less dangerous productsInhibitor- something that slows or stops a reaction-food preservatives
37. Catalyst example2 O3 3 O2Ozone will decompose into elemental oxygen, however this process is very slow.Chlorine acts as a catalyst as shown in this two step reaction2 O3 + 3 Cl2 6 ClO6 ClO 3 O2 + 3 Cl2 ClO is an intermediate, something formed in the middle of the reaction that is later consumed.Chlorine is a catalyst because it is a reactant in the first step, but a product in the last step. So it isn’t used up during the reaction.
38. Forwards and backwardsMost reactions can go forwards or backwardsNeutralization equationH3O+ + OH- 2 H2O Self ionization of water2 H2O H3O+ + OH-
39. EquilibriumIn water, both of those reactions are occurring simultaneously.Equilibrium is when the forward and backward reactions are occurring at the same rate.This will cause a stable amount of product and reactant to be present. No net change is occurring when it is at equilibrium. (dynamic equilibrium)The amount of product and reactant do NOT have to be equal!
40. Representing equilibriumIt is normally represented with a double arrow2 H2O H3O+ + OH- This reaction comes to equilibrium when [H3O+ ] = 1 x10-7 M and [OH- ] = 1 x10-7 M (assuming the solution is neutral)you won’t have to calculate this.
41. Le Châtelier’s Principle~whenever stress is applied/changes are made to a system at equilibrium, a new equilibrium will be obtained to balance this stress/change.stress is a change in temperature, pressure, or concentration of some component.This will change the rate of reaction of either the forward or backward reactionSo you will see an increase in the concentration of the substances on one side of the equation, and a decrease on the other.This will “shift” the equation to the right or left.
42. ExamplesEndothermic reactions absorb heat, i.e. they need heat to react.If the solution is heated prior to the reaction (stress)…It will react more quicklySo the equation will be forced to the right (product side)If the reaction is cooled, it will be forced to the left (reactant side)
43. Equilibrium
44. EquilibriumSystems at equilibrium are still dynamic (changing). However, no NET CHANGE will be observed.A system is at equilibrium when the rate of the forward reaction is equal to the rate of the reverse reaction.
45. Changing concentration2 H2O H3O+ + OH-If I add more waterIt will force the reaction to the right Which means more hydronium and hydroxide will be producedThis is dilution (making the ratio of hydronium/hydroxide closer)
46. EquilibriumAdd water 2 H2O H3O+ + OH-Stress + X 0 0Shift -2y +y +yFinal +X - 2y + y +y*where X is the amount of H2O added Since the stress was added to the left, we must take from the left and give to the right to relieve the stress*y is the amount of water that “shifts” over to make more hydronium and hydroxide. For every 2 H2O molecules, one H3O+ and OH- is produced
47. What this means…Add water 2 H2O H3O+ + OH-Final + X - 2y + y +yThe overall amount of water increased because X is always larger than y (with any coefficient).We increased H3O+ because +y is an increase We increased OH- because +y is an increaseThe amount H3O+ increased is equal to the amount OH- increased
48. The only equilibrium calculationThat you will have to do with numbers is:[OH-] [H3O+ ] = KwKw is the equilibrium constant for water, it equals 1 x 10-14 MWe have already used the equation
49. More Le Châtelier’s If I add an acid to the equilibrium… 2 H2O H3O+ + OH-Stress 0 +X 0Shift +2y -y -yFinal + 2y +X- y -y *Where X is larger than 2yso adding acid will decrease the [OH-], only slightly increase the[H3O+ ], and increase water.
50. 2 H2O H3O+ + OH-If I remove hydroxide from the solution… 2 H2O H3O+ + OH-Stress 0 0 -XShift -2y +y +yFinal - 2y + y -X +y *Where X is larger than 2ySo removing hydroxide increases [H3O+], only slightly decreases [OH-], and decrease the water
51. Different equationAdding ammonia, NH3, to the equilibrium 2 NH3 3 H2 + N2 Stress +X Change -2y +3y +yFinal +X-2y +3y +y *where X is larger than 2yEverything increases Note that the amount H2 increases 3x as much as N2
52. With heatIf I cool the following equilibrium Heat+ Co2+ + 4 Cl- CoCl42- stress -x 0 0 0Shift +y +4y -yFinal +y +4y -y So cooling the solution will cause more Co2+ & Cl- and less CoCl42- to form
53. Conjugate acids and bases
54. Different definitions of acids and basesAcids are proton donors (Brønsted Lowry definition)they generate H3O+ in water (Arrhenius definition)Bases are proton acceptorsthey generate OH- in waterwhich is an acid/base?HF + H2O H3O+ + F-NaHCO3 + H2O Na+ +H2O + CO2 + OH-
55. Follow the protonHF + H2O H3O+ + F-NaHCO3 + H2O Na++ H2O+CO2 +OH-Joining equilibrium to acid base…What about the reverse reaction?H+H+H+H+
56. Conjugate acids and basesWhen you run the reverse reaction you find the products are also acids and bases. The acids and bases that are formed are called conjugate acids or basesH2O + HF H3O+ + F-base acid conjugate acid conjugate baseNaHCO3 + H2O Na+ +H2O + CO2 +OH-base acid CA CB
57. Label Acid, Base, Conjugate Acid, Conjugate BaseHClO3 + H2O ClO3- +H3O+ ClO- + H2O HClO + OH-HSO4- + H2O SO42- +H3O+ LiOH + H2O Li+ + H2O + OH-
58. Strong and Weak Acids and BasesA strong acid or base is one that completely dissociates into water, making the most possible H3O+ or OH- that is possibly can.HCl H+ + Cl-A weak acid or base is one that does not completely dissociate, and is an equilibrium reaction.HF ⇌ H+ + F-
59. Conjugate acids and bases …Conjugate acids and bases determine if an acid or base is strong or weak.If the conjugate acid/base readily reacts to run the reverse reaction it is a weak acid/base.If it does not react in the reverse reaction the acid or base is strong.
60. Strong acidsAcidformulaNitric AcidHNO3Sulfuric AcidH2SO4Hydrochloric acidHCl
61. Strong BasesNameFormulaNameFormulaSodium HydroxideNaOHCalcium HydroxideCa(OH)2Potassium HydroxideKOHStrontium HydroxideSr(OH)2Barium HydroxideBa(OH)2these make a lightning bolton the periodic table!
62. More with conjugate acids/basesH2SO4 + H2O H3O+ + HSO4-Sulfuric acid is a strong acid so its conjugate base, HSO4-, will not run the reverse reaction. HSO4 - is actually an acid in water.HSO4 - + H2O H3O+ + SO42-SO42- will run the reverse reaction, so it is a weak acid
63. Other weak acids and basesWeak AcidsAcetic Acid (vinegar)Citric AcidAscorbic Acid (vitamin C)Boric AcidCarbonic AcidWeak BasesSodium BicarbonateAmmoniaSodium Hypochlorite (bleach)
64. Danger!!!Strong and Weak acids and bases do NOT necessarily tell you how dangerous they are.Concentration is the most important factor for determining danger.Ammonia is a weak base, if it is highly concentrated it can burn you.Dilute hydrochloric acid (less than 1 M) is not particularly dangerous
65. What is waterWater is either an acid or base depending on the situation.Anything that is either an acid or a base is called amphoteric.Several things are amphoteric, like parts of you.
66. Donating ProtonsHydrochloric acid (HCl) can donate 1 proton, so it is called a monoprotic acid.Sulfuric acid (H2SO4) can donate 2 protons, so it is called a diprotic acid.Phosphoric acid (H3PO4) can donate 3 protons, so it is called a triprotic acid.
67. Indicators
68. Weak acids and bases can act as an indicatorcan be forced the other waySo ammonia…NH3 + H2O NH4++OH-Ammonia is a gas with a distinct odorAmmonium and hydroxide are both odorless.If base is added to the solution you will smell ammonia, if hydroxide is removed you won’t.
69. Pet Stain ProblemUrine has ammonia in it.Most cleansers are basicNH3 + H2O ⇌ NH4++OH-If I stress this equilibrium by adding a base…It shifts to the left causing more ammonia to form. Animals sense of smell is better so they fine the same spot and mark it again.That is why there are special cleansers (acidic) for pet stains
70. IndicatorsIndicators are a substance that change color in the presence of (whatever they check for)They do this because of Le Châtelier’s principle. All you need an equilibrium reaction with different colored products and reactants.The pen used to check for counterfeit money is a starch indicator
71. How an acid base indicator worksA generic indicator will follow this reaction, HId is the reactant indicator, and Id- is its productHId + H2O H3O+ + Id- The color differences are important in an acidic solution (high H3O+) you see reactantHId + H2O H3O+ + Id-in a basic solution (low H3O+) you see productHId + H2O H3O+ + Id-
72. Acid Base indicatorsAcid base indicators change color at certain pH levelsThey don’t have to change at 7 (most don’t)Universal indicator solution (phenolphthalein, bromthymol blue and methyl red dissolved in ethanol and water) changes color at each integral pH value
73. Other pH indicatorsLitmus and phenolphthalein are indicatorsRed cabbage has a pigment that changes colors at different pH values
74. BuffersBuffers are solutions that don’t change in pH when acids or bases are added.They use weak acids/bases and Le Châtelier’s principle.WA = weak acidHWA + H2O H3O+ + WA-
75. How?pH is determined by the concentration of H3O+Concentration is measured by mol /L Moles of H3O+ / L (primarily of) H2O
76. What it doesadding H3O+ should increase [H3O+]However, this forces the equation to the left, decreasing H3O+ and increasing H2Oso the [H3O+] remains constantRemoving H3O+ (adding a base) should decrease [H3O+]However, this forces the equation to the right, increasing H3O+ and decreasing H2OSo again, there is no change to [H3O+]There is a breaking point where the pH will change.
77. What does this have to do with my life?Your blood is a buffered solution The pH must remain between 7.35-7.45Outside of that range can kill youbelow this range is called acidosisabove is called alkalosis
78. Buffered Productsmedications (Bufferin)Shampoos, body soapsAll are buffered to be near your body pH so they won’t cause a major disruption.