Acids and Bases Chapter 19. Ions in Solution Aqueous solutions contain H + ions and OH - ions If a...
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Transcript of Acids and Bases Chapter 19. Ions in Solution Aqueous solutions contain H + ions and OH - ions If a...
Ions in SolutionIons in Solution
Aqueous solutions contain HAqueous solutions contain H+ + ions and ions and OHOH- - ionsions
If a solution has more HIf a solution has more H+ + ions than OHions than OH- -
ions it is acidicions it is acidic If a solution has more OHIf a solution has more OH- - ions than Hions than H+ +
ions it is basicions it is basic If a solution has the same number of OHIf a solution has the same number of OH- -
ions and Hions and H+ + ions it is neutralions it is neutral
Properties of AcidsProperties of Acids
Properties acidsProperties acids – – Produce HProduce H++ ions when dissolved in water ions when dissolved in water taste sour taste sour Turn Blue Litmus paper PinkTurn Blue Litmus paper Pink React with metals to produce Hydrogen GasReact with metals to produce Hydrogen Gas
good at dissolving things (food in stomach, teeth good at dissolving things (food in stomach, teeth to form cavities, mineral deposits in coffeemaker)to form cavities, mineral deposits in coffeemaker)
Have a pH of 0 to < 7Have a pH of 0 to < 7 Conduct electricityConduct electricity
Properties of BasesProperties of Bases
Properties basesProperties bases – – taste bittertaste bitter feel slipperyfeel slippery tend to produce OHtend to produce OH-- ions when placed in ions when placed in
waterwater turn Red Litmus Paper Blueturn Red Litmus Paper Blue Have a pH of 7 to 14Have a pH of 7 to 14 Conduct electricityConduct electricity
Two models of Acids and Two models of Acids and BasesBases
ArrheniusArrhenius Bronsted-LowryBronsted-Lowry Two similar but different explanations, Two similar but different explanations,
both are correctboth are correct
ArrheniusArrhenius
Acid Acid - produces H - produces H++ in aqueous solution in aqueous solution HCl (g) HCl (g) H H+ + (aq) + Cl(aq) + Cl- - (aq)(aq)
BaseBase – produces OH – produces OH-- in aqueous solution in aqueous solution NaOH (s) NaOH (s) Na Na+ + (aq) + OH(aq) + OH- - (aq)(aq)
Explains most Acids and Bases, but not Explains most Acids and Bases, but not allall
Acid-Base Neutralization Acid-Base Neutralization ReactionReaction
When an acid and a base are mixed When an acid and a base are mixed together:together:
acid + base acid + base A salt and water are formed:A salt and water are formed:
a salt + watera salt + water remember remember a salta salt is any ionic compound is any ionic compound
ExamplesExamples
HCl (aq) + NaOH (aq) HCl (aq) + NaOH (aq) NaCl (aq) + H NaCl (aq) + H22O (l)O (l)
AcidAcid + Base+ Base A Salt + WaterA Salt + Water 2HCl(aq) + Ca(OH)2HCl(aq) + Ca(OH)22(aq) (aq) CaCl CaCl22(aq) + 2 H(aq) + 2 H22O(l)O(l)
AcidAcid + Base+ Base A Salt + WaterA Salt + Water
Bronsted-Lowry ModelBronsted-Lowry Model
Ammonia (NHAmmonia (NH33) is a base.) is a base.
It does not contain OHIt does not contain OH-- in it. in it. So according in Arrhenius it isn’t a base.So according in Arrhenius it isn’t a base. But when placed in water it produces OH, But when placed in water it produces OH,
so it must be a base.so it must be a base.
Bronsted-Lowry ModelBronsted-Lowry Model
The Bronsted-Lowry model focuses on The Bronsted-Lowry model focuses on HH++ ion ion
AcidAcid – H – H++ donor donor When placed in water Acids give HWhen placed in water Acids give H+ + awayaway HCl (g) + HHCl (g) + H22O (l) O (l) Cl Cl-- (aq) + H (aq) + H33OO++ (aq) (aq)
HH33OO++ (aq) is called the (aq) is called the Hydronium ionHydronium ion
BaseBase – H – H++ acceptor acceptor NHNH3 3 (aq) + H(aq) + H22O (l) O (l) NH NH44
++ (aq) + OH(aq) + OH--
Acid-Base PairsAcid-Base Pairs
In Bronsted-Lowry Acids and Bases you In Bronsted-Lowry Acids and Bases you must always have a pairmust always have a pair Every Acid must have a Conjugate BaseEvery Acid must have a Conjugate Base Every Base must have an Conjugate AcidEvery Base must have an Conjugate Acid
HCl (g) + HHCl (g) + H22O (l) O (l) Cl Cl-- (aq) + H (aq) + H33OO++ (aq) (aq)
Acid Base Con Base Con AcidAcid Base Con Base Con Acid HCl is an Acid and produces ClHCl is an Acid and produces Cl-- HH22O must be a Base and produces HO must be a Base and produces H33OO++
More on PairsMore on Pairs
HI(s) + HHI(s) + H22O(l) O(l) H H33OO++(aq) + I(aq) + I--(aq)(aq)
AcidAcid Base Base C.A. C.B. C.A. C.B. HH22SOSO44(s) + H(s) + H22O(l) O(l) H H33OO++(aq) + HSO(aq) + HSO44
--
(aq)(aq) AcidAcid Base Base C.A. C.B. C.A. C.B.
Strong AcidsStrong Acids
Strong acid Strong acid - reacts completely with water to - reacts completely with water to produce ions; no molecules are leftproduce ions; no molecules are left
Example: HCl + HExample: HCl + H22O O HH33OO++ + Cl + Cl-- The Six Strong Acids: The Six Strong Acids: 1.1. HCl (hydrochloric acid)HCl (hydrochloric acid)2.2. HBr (hydrobromic acid)HBr (hydrobromic acid)3.3. HI (hydroiodic acid)HI (hydroiodic acid)4.4. HH22SOSO44 (sulfuric acid) (sulfuric acid)5.5. HNOHNO33 (nitric acid) (nitric acid)6.6. HClOHClO44 (perchloric acid) (perchloric acid)
Strong acids:Strong acids:
HCl + HHCl + H22O O H H33OO++ + Cl- + Cl-
Remember, strong acids ionize completely in water. The reaction goes all the way to the right. A single arrow is used. There are virtually no HCl molecules left intact.
Strong acids:Strong acids:
HCl + HHCl + H22O O H H33OO++ + Cl- + Cl-
Looking at the equation above, with the single arrow, is Cl- a strong base or a weak base?
Weak AcidsWeak Acids
weak acidweak acid – reacts only slightly with – reacts only slightly with water to produce ions; mostly molecules water to produce ions; mostly molecules leftleft
HF + HHF + H22O O H H33OO++ + F+ F--
HH22COCO33 + H + H22O O H H33OO++ + HCO+ HCO33--
Notice: Only one H comes off at a timeNotice: Only one H comes off at a time
Strong BasesStrong Bases
Strong Base Strong Base - reacts completely with - reacts completely with water to produce ions; no molecules are water to produce ions; no molecules are leftleft
Strong Bases: Strong Bases: Group 1 metals and Sr, Ba, and Ra with OH Group 1 metals and Sr, Ba, and Ra with OH
presentpresent Examples NaOH, KOH, CsOH, Ba(OH)Examples NaOH, KOH, CsOH, Ba(OH)22
Weak BasesWeak Bases
weak Basesweak Bases – reacts only slightly with – reacts only slightly with water to produce ions; mostly molecules water to produce ions; mostly molecules leftleft
Examples:Examples: NHNH33 + H + H22O O NH NH44
++ + OH + OH--
Fe(OH)Fe(OH)33 + H + H22O O Fe Fe 3+ 3+ + 3 OH+ 3 OH--
General ruleGeneral rule: The : The conjugate base of a conjugate base of a strong acid is a weak strong acid is a weak base.base.Similarly, the conjugate Similarly, the conjugate acid of a strong base is a acid of a strong base is a weak acid.weak acid.
One more reminder:One more reminder:
“Weak” does not mean the same “Weak” does not mean the same thing as “diluted.”thing as “diluted.”
HCl, for example is always a strong HCl, for example is always a strong acid. If you add 1000 liters of water acid. If you add 1000 liters of water to it, it will be diluted, but still to it, it will be diluted, but still strong because what little there is strong because what little there is will be will be completely dissociated.completely dissociated.
Concentrated Vs DiluteConcentrated Vs Dilute
Concentrated means that there is a lot of Concentrated means that there is a lot of Acid/Base molecules for the amount of Acid/Base molecules for the amount of water or that the Molarity is Highwater or that the Molarity is High Concentrated HCl is 16 MConcentrated HCl is 16 M
Dilute means that there are not many Dilute means that there are not many Acid/Base molecules or that the Molarity Acid/Base molecules or that the Molarity is Lowis Low Diluted HCl would be 0.1 MDiluted HCl would be 0.1 M
Naming AcidsNaming Acids
Look at the names of these acids – can Look at the names of these acids – can you come up with the rule?you come up with the rule?
HH22SOSO44: sulfur: sulfuricic acid acid
HNOHNO33: nitr: nitricic acid acid
HH33POPO44: phosphor: phosphoricic acid acid
Naming acidsNaming acids
Rule #1: If the acid comes from a Rule #1: If the acid comes from a polyatomic ion that ends in “ate,” the acid polyatomic ion that ends in “ate,” the acid is named ____-ic.is named ____-ic.
HH22SOSO44: sulfur: sulfuricic acid (from sulfate) acid (from sulfate)
HNOHNO33: nitr: nitricic acid (from nitrate) acid (from nitrate)
HH33POPO44: phosphor: phosphoricic acid (from phosphate) acid (from phosphate)
Naming AcidsNaming Acids
Rule #2: If the acid does not have oxygen Rule #2: If the acid does not have oxygen in it, then name it…in it, then name it…
hydro + second element + ichydro + second element + ic
Example:Example:
HCl is hydrochloric acid.HCl is hydrochloric acid.
What would HBr be? HWhat would HBr be? H22S?S?
Water as an Acid and a Water as an Acid and a BaseBase
amphotericamphoteric – describes substance that – describes substance that can act as an acid or as a basecan act as an acid or as a base
Example: HExample: H22O (see previous Bronsted O (see previous Bronsted Lowry examples)Lowry examples)
Arrhenius: Arrhenius: HH22O O H H++ + OH + OH--
Bronsted Lowry: Bronsted Lowry: HH22O + HO + H22O O H H33OO++ + OH + OH--
Strength of Acids/BasesStrength of Acids/Bases
pH Scale relates strengths of acids and pH Scale relates strengths of acids and basesbases
pH 0 to 7 – AcidpH 0 to 7 – Acid pH = 7 – NeutralpH = 7 – Neutral pH 7 to 14 – BasepH 7 to 14 – Base pH can only be from 0 to 14pH can only be from 0 to 14 pH= -log[HpH= -log[H++]]
Basic
Acidic Neutral
100
10-
1
10-
3
10-
5
10-
7
10-
9
10-
11
10-
13
10-
14
[H+]
0 1 3 5 7 9 11
13
14
pH
Basic
100
10-
1
10-
3
10-
5
10-
7
10-
9
10-
11
10-
13
10-
14
[OH-]
01357911
13
14
pOH
pHpH
pH= -log[HpH= -log[H++]] Used because [HUsed because [H++] is usually very small] is usually very small As pH decreases, [HAs pH decreases, [H++] increases ] increases
exponentiallyexponentially Sig figs only the digits after the decimal Sig figs only the digits after the decimal
place of a pH are significantplace of a pH are significant [H[H++] = 1.0 x 10] = 1.0 x 10-8-8 pH= 8.00 3 sig figs pH= 8.00 3 sig figs
How to find pHHow to find pH
Punch in calculator: [HPunch in calculator: [H++] or number, log, ] or number, log, +/– +/–
Example: Example: Find pH if [HFind pH if [H++] = 1.0 x 10] = 1.0 x 10-5-5 M M pH = - log(1.0 x 10pH = - log(1.0 x 10-5-5) = 5.00) = 5.00 Punch in + / –, log, 1.0 EXP - 5, Enter Punch in + / –, log, 1.0 EXP - 5, Enter
[H[H++] Concentration] Concentration
If you know the pH, you can determine If you know the pH, you can determine the Molarity of Hthe Molarity of H++ Ions in the solution. Ions in the solution.
Since pH= -log [HSince pH= -log [H++]] Then [HThen [H++] = 10] = 10-pH-pH
What is the Hydrogen Ion concentration What is the Hydrogen Ion concentration of a solution that has a pH of 7.00?of a solution that has a pH of 7.00?
[H[H++] = 10] = 10-7.00-7.00 = 1.0 x 10 = 1.0 x 10-7 -7 MM
How to find [HHow to find [H++]]
Given pH, find [H]; Punch in pH or number, Given pH, find [H]; Punch in pH or number, +/– , 10+/– , 10xx or 2nd log or 2nd log
Example: If pH is 9.0, find [HExample: If pH is 9.0, find [H++] ] pH = -log [HpH = -log [H++] ] Punch in 10Punch in 10xx or 2nd log, +/– , 9.0 or 2nd log, +/– , 9.0 [H] = 1.0 x 10[H] = 1.0 x 10-9-9 M M
What if it has OHWhat if it has OH-- but not but not HH++??
14 = pH + pOH14 = pH + pOH 1.0 x 101.0 x 10-14-14 = [H = [H++] x [OH] x [OH--]] What is the pH of a solution that has a What is the pH of a solution that has a
pOH of 5.00?pOH of 5.00? 14 = pH + 5.00 or 14 – 5.00 = 9.0014 = pH + 5.00 or 14 – 5.00 = 9.00
What would the [HWhat would the [H++] be?] be? [H[H++] = 10] = 10-9.00-9.00 = 1.0 x 10 = 1.0 x 10-9 -9 MM
pOHpOH
Not all substances make [HNot all substances make [H++], some ], some make OHmake OH--
pOH= -log[OHpOH= -log[OH--]] 14 = pH + pOH14 = pH + pOH Sig figs only the digits after the decimal Sig figs only the digits after the decimal
place of a pH are significantplace of a pH are significant [OH[OH--] = 1.0 x 10] = 1.0 x 10-8-8 pOH= 8.00 3 sig figs pOH= 8.00 3 sig figs pH = 14 – 8.00 = 6.00pH = 14 – 8.00 = 6.00
Finding OH- if you have Finding OH- if you have H+H+
• 1.0 x 10-14 = [H+][OH-]1.0 x 10-14 = [H+][OH-]• If you hydrogen ion concentration is If you hydrogen ion concentration is
2.50 x 10-5, what is the Hydroxide ion 2.50 x 10-5, what is the Hydroxide ion concentration?concentration?
• 1.0 x 10-14 = [2.50 x 10-5][OH-]1.0 x 10-14 = [2.50 x 10-5][OH-]• 1.0 x 10-141.0 x 10-14 = [OH-] = [OH-]• 2.50 x 10-52.50 x 10-5 = 4.0 x 10-10= 4.0 x 10-10