4.8 Acid-Base 4.8 Acid-Base ReactionsReactions
DefinitionsDefinitions
Arrhenius:Arrhenius: Acid- produces HAcid- produces H++ when dissolved in water when dissolved in water Base- produces OHBase- produces OH-- when dissolved in water when dissolved in water
Bronsted-LowryBronsted-Lowry:: AcidAcid- H- H++/proton donor/proton donor BaseBase- H- H++/proton acceptor/proton acceptor
Since HSince H22O is a non-electrolyte, large O is a non-electrolyte, large amounts of OHamounts of OH-- and H and H++ cannot exist in cannot exist in solution without combiningsolution without combining
Lewis ModelLewis Model
even more general than Bronsted-even more general than Bronsted-Lowry Lowry
acidacid electron pair acceptorelectron pair acceptor has empty atomic orbitalshas empty atomic orbitals
basebase electron pair donorelectron pair donor has lone pairhas lone pair
HA ----> H3O+ + A-
ArrheniusAcidH2O
O
HH
HA
O
HHH
+
+ A-
Lewis BaseLewis Base
Monoprotic acid: HClMonoprotic acid: HCl
HClHCl(aq) (aq) + NaOH+ NaOH(aq) (aq) ---> --->
HH22OO(l) (l) + NaCl+ NaCl(aq)(aq)
HH++ + Cl + Cl-- + Na + Na++ + OH + OH-- ---> --->
HH22O + NaO + Na++ + Cl + Cl--
HH++ + OH + OH-- ---> H ---> H22OO
Diprotic acid: HDiprotic acid: H22SOSO44
Polyprotic acid: HPolyprotic acid: H33POPO44
Strong AcidsStrong Acids
Know these!!!Know these!!!
1.1. HCl – hydrochloric acidHCl – hydrochloric acid2.2. HBr – hydrobromic acidHBr – hydrobromic acid3.3. HI – hydroiodic acidHI – hydroiodic acid
4.4. HH22SOSO4 4 – sulfuric acid– sulfuric acid
5.5. HNOHNO3 3 – nitric acid– nitric acid
6.6. HClOHClO4 4 – perchloric acid– perchloric acid
Strong BasesStrong Bases
All are metal hydroxides – especially All are metal hydroxides – especially group I and II group I and II Dissociate completely in waterDissociate completely in water List List
Neutralization ReactionsNeutralization Reactions
Metathesis reaction Metathesis reaction AKA Double AKA Double replacement or displacement replacement or displacement
Typically involves ion transfer (not Typically involves ion transfer (not redox)redox)
Involves reaction of HInvolves reaction of H++ (or H (or H33OO++) and ) and OHOH- - to form water moleculesto form water molecules
Arrhenius acid/base Arrhenius acid/base
reactionreaction
NeutralizationNeutralization
acid + base ---> Hacid + base ---> H22O + a saltO + a salt
HA + MOH ---> HHA + MOH ---> H22O + MAO + MA
Salt = ionic compound formed Salt = ionic compound formed from the anion of an acid and the from the anion of an acid and the cation from a basecation from a base
NeutralizationNeutralizationExample 4.13 p. 160Example 4.13 p. 160
28.0 mL of 0.250 M HNO28.0 mL of 0.250 M HNO33 is is added to 53.0 mL of 0.320 M added to 53.0 mL of 0.320 M KOH. Calculate the grams of KOH. Calculate the grams of water formed. What is the water formed. What is the concentration of Hconcentration of H++ and OH and OH-- ions ions after reaction is complete?after reaction is complete?
Example 1Example 1
Write balanced net ionic equation.Write balanced net ionic equation.Molecular:Molecular:
HNOHNO33(aq) + KOH(aq) (aq) + KOH(aq) H H22O(l) + KNOO(l) + KNO33(aq)(aq)
Complete Ionic:Complete Ionic:
HH++(aq) + NO(aq) + NO33--(aq) + K(aq) + K++(aq) + OH(aq) + OH--(aq) (aq)
HH22O(l) + KO(l) + K++(aq) + NO(aq) + NO33--(aq)(aq)
Net Ionic:Net Ionic:
HH++(aq) + OH(aq) + OH--(aq) (aq) H H22O(l)O(l)
Example 1Example 1
Find number of moles of each reactantFind number of moles of each reactant
HH++::
OHOH--::
molHmolHNO
molH
L
molHNO 3
3
3 1000.71
1
1
250.0L 0.0280
molOHmolKOH
molOH
LKOH
molKOHLKOH 21070.1
1
1
1
320.00530.0
Example 1Example 1
Find limiting reactantFind limiting reactant
Since we have extra OHSince we have extra OH-- left, H left, H++ is the LR. is the LR.
Find the grams of product made.Find the grams of product made.
neededmolOHmolH
molOHmolH
33 1000.7
1
11000.7
OgHOmolH
OgH
molH
OmolHmolH 2
2
223 126.01
02.18
1
11000.7
Example 1Example 1
Find the concentrations of HFind the concentrations of H++ and OH and OH--
Since H+ was the limiting reactant, there Since H+ was the limiting reactant, there should be none left.should be none left.
We already calculated how much OH- will be We already calculated how much OH- will be used, so to find the amount left, we can used, so to find the amount left, we can subtract.subtract.
To find the molarity, divide the moles by total To find the molarity, divide the moles by total volume:volume:
0H
molOH0100.000700.00170.0
MOHLL
molOHOH 123.0
0530.00280.0
0100.0
TitrationsTitrations volumetric analysis-volumetric analysis- technique technique
used to find amount of certain used to find amount of certain substance by doing a titrationsubstance by doing a titration
titrationtitration- when you add a - when you add a certain volume of a solution certain volume of a solution with a known concentration with a known concentration ((titranttitrant) to a certain amount of ) to a certain amount of solution being analyzed solution being analyzed ((analyteanalyte))
TitrationsTitrations
equivalence point-equivalence point- when there are when there are equal moles of each reactant presentequal moles of each reactant present
indicatorindicator- substance that changes - substance that changes color near equivalence pointcolor near equivalence point
end point-end point- when indicator changes when indicator changes colorcolor
TitrationsTitrations
For a good titration:For a good titration: reaction between titrant and analyte must be reaction between titrant and analyte must be
knownknown equivalence point must be marked accuratelyequivalence point must be marked accurately volume of titrant needed for equivalence must volume of titrant needed for equivalence must
be knownbe known phenolphthalein- phenolphthalein-
common indicator used common indicator used clear until acid is consumed and one drop of clear until acid is consumed and one drop of
excess base is added; turns pinkexcess base is added; turns pink
Neutralization Titration - Neutralization Titration - Example 4.14 p. 162 - 163Example 4.14 p. 162 - 163
To standardize a sodium hydroxide To standardize a sodium hydroxide solution, a student plans to titrate the solution, a student plans to titrate the solution with a monoprotic acid, KHP solution with a monoprotic acid, KHP (KHC(KHC88HH44OO44, potassium hydrogen , potassium hydrogen phthalate). She dissolves 1.3009 g of KHP phthalate). She dissolves 1.3009 g of KHP in water, adds phenolphthalein, and in water, adds phenolphthalein, and titrates to the endpoint. It took 41.20 mL titrates to the endpoint. It took 41.20 mL of sodium hydroxide to titrate the KHP of sodium hydroxide to titrate the KHP solution. solution.
Calculate the concentration of NaOH.Calculate the concentration of NaOH.
Example 2Example 2
Write the balanced net ionic equation:Write the balanced net ionic equation:
NaOH(aq) + KHP(aq) NaOH(aq) + KHP(aq) NaKP(aq) + H NaKP(aq) + H22O(l)O(l)
NaNa++(aq) + OH(aq) + OH--(aq) + KHP(aq) (aq) + KHP(aq) NaNa++(aq) + KP(aq) + KP--(aq) + H(aq) + H22O(l)O(l)
OHOH--(aq) + KHP(aq) (aq) + KHP(aq) H H22O(l) + KPO(l) + KP--(aq)(aq)
Example 2Example 2
Find the moles of HFind the moles of H++ in the KHP: in the KHP:
Find the moles of NaOH used:Find the moles of NaOH used:
Find molarity of NaOH used:Find molarity of NaOH used:
molHmolKHP
molH
gKHP
molKHPgKHP 0063701.0
1
1
22.204
13009.1
molNaOHmolOH
molNaOH
molH
molOHmolH 0063701.0
1
1
1
10063701.0
MNaOHL
molNaOHNaOH 1546.0
04120.0
0063701.0
Neutralization Analysis Neutralization Analysis Example 4.15 p. 163 – 164 Example 4.15 p. 163 – 164
A 0.3518 g mixture of CClA 0.3518 g mixture of CCl44 and and HCHC77HH55OO22 was mixed with water was mixed with water and titrated by 10.59 mL of and titrated by 10.59 mL of 0.1546 M NaOH. 0.1546 M NaOH.
Find the percent by mass of Find the percent by mass of HCHC77HH55OO22 in the original sample. in the original sample.
Example 3Example 3
Write the net ionic equationWrite the net ionic equation
HCHC77HH55OO22(aq) + OH(aq) + OH--(aq) (aq)
HH22O(l) + CO(l) + C77HH55OO22--(aq)(aq)
Find moles of OH- used:Find moles of OH- used:
molOHmolNaOH
molOH
L
molNaOHL 001637.0
1
1
1
1546.001059.0
Example 3Example 3
Find moles of HCFind moles of HC77HH55OO22 used: used:
Find the grams of HCFind the grams of HC77HH55OO22::
Find percent by mass:Find percent by mass:
257257 001637.0
1
1
1
1001637.0 OHmolHC
molH
OHmolHC
molOH
molHmolOH
257257
257257 1999.0
1
2.122001637.0 OHgHC
OHmolHC
OHgHCOHmolHC
257257 %83.56
3518.0
1999.0% OHHC
gtotal
OHgHC