lecture 19.1b- bronsted-lowry acids & bases
DESCRIPTION
Section 19.1 lecture (part B) for Honors & Prep ChemistryTRANSCRIPT
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Bellwork- concentration review
How many moles of H+ are in 250ml of 3MHCl?
How many moles of OH- are produced when25g of NaOH is dissolved in 250ml ofwater?
What is the molarity of the NaOH solution?
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Arrhenius concept
Acids make H+
Bases make OH-
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The Brønsted-Lowry definitionof
ACIDS AND BASES
Acids donate protons (H+)HCl H+ + Cl-
Bases accept protons (H+)NH3 + H+ NH4
+
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The Bronsted- Lowry model ismore inclusive than the Arrheniusmodel.
NH3 + H+ NH4+
Ammonia is a Bronsted-Lowrybase, but does not dissociate tomake OH-
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Why Ammonia is a Base19.1
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HA + H2O H3O+ + A-
Acid base conjugate conjugateacid base
An acid donates a proton forming itsconjugate base. HA A-
A base accepts a proton forming itsconjugate acid. NH3 NH4
+
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HA A-
Acid conjugate baseA- is ready to accept a proton, it is abase.
NH3 + H+ NH4+
Base conjugate acid
NH4+ has a proton to donate. It is an
acid.
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Conjugate Acids and Bases
•A conjugate acid is the particleformed when a base gains ahydrogen ion.
•A conjugate base is the particle thatremains when an acid has donated ahydrogen ion.
19.1
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•A conjugate acid-base pairconsists of two substances relatedby the loss or gain of a singleproton.
•A substance that can act as bothan acid and a base is said to beamphoteric.
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Water is amphoteric.Water can be an acid or a base
H2O H+ + OH-
Water can ionize and donate aproton.
H2O H3O+
As a base, water accepts a protonforming the hydronium ion.
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A conjugate acid-base pair consists oftwo substances related to each other bythe donating and accepting of a proton
Are the following pairs conjugate acid-base pairs?
a. H2O H3O+
b. OH- HNO3
c. HC2H3O2 C2H3O2-
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Brønsted-Lowry Acidsand Bases
19.1
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Identify conjugate acid base pairs
HCl + NH3 NH4+ + Cl-
HSO4- + OH- H2O + SO42-
NH3 + H2O NH4+ + OH-
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Lewis Acids and Bases
Lewis definition
an acid accepts a pair of electrons
a base donates a pair of electrons.
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Lewis Acids and Bases
•A Lewis acid is a substance that canaccept a pair of electrons to form acovalent bond.
•A Lewis base is a substance that candonate a pair of electrons to form acovalent bond.
19.1
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Animation 25 Compare the three importantdefinitions of acids and bases.
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Lewis Acids and Bases19.1
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1. Which of the following is NOT acharacteristic of acids?
a. taste sour
b. are electrolytes
c. feel slippery
d. affect the color of indicators
19.1 Section Quiz.
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2. Which compound is most likely toact as an Arrhenius acid?
a. H2O
b. NH3.
c. NaOH.
d. H2SO4.
19.1 Section Quiz.
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3. A Lewis acid is any substance thatcan accept
a. a hydronium ion.
b. a proton.
c. hydrogen.
d. a pair of electrons.
19.1 Section Quiz.
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pHThe pH scale measures thehydrogen ion
concentration[H+] of asolution.
A pH of 7 is neutral
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A pH less than 7 is acidic (litmus red)
A pH greater than 7 is basic (litmusblue)
The pH scale ranges from below zero (veryacidic) to above14 (very basic)
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The pH scale is not linear.
The pH scale is logarithmic.
pH = -log[H+]
[H+] = 1.0 x 10-2 pH = 2 very acidic
[H+] = 1.0 x 10-3 pH = 3 acidic
A solution with pH of 2 contains 10 timesas much H+ as a solution with pH of 3.
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Acidic = more H+ than OH-
Basic = more OH- than H+
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From pH 0 to pH 14 theH+ concentration decreases100,000,000,000,000 times!!
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Measuring pH
An indicator is a valuable toolfor measuring pH because itis a different color in acidicsolution than when in base.
19.2
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Measuring pH
Phenolphthaleinchanges fromcolorless topink at pH7–9.
19.2
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Measuring pH19.2
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Measuring pH
Universal Indicators
19.2
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Measuring pH
– pH Meters
19.2
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Solu%on RedLitmus
BlueLitmus
pHpaper Universalindicator
Acid,Base,orneutral?
lemonjuice(diluted)
bakingsoda+H2O
Drano(NaOH)(diluted)
Lysol(diluted)
Vinegar