Acids and Bases - Honors Chemistry...Acids: 1. Blue litmus turns red 2. Bromothymol blue turns...
Transcript of Acids and Bases - Honors Chemistry...Acids: 1. Blue litmus turns red 2. Bromothymol blue turns...
H O N O R S C H E M I S T R Y
UNIT 9 - ACIDS AND BASES
Name the following acids:
HCl H2SO4 H2SO3 H2S
Name the following bases:
NaOH Ca(OH)2 Cu(OH)2 NH4OH
WARM UP 11/25: ACID/BASE NAMING
COMMON ACIDS
• Sulfuric Acid (H2SO4)• “battery acid”• Most commonly
produced industrial chemical in the world
• Nitric Acid (HNO3)• Volatile, unstable
liquid• Used in explosives• Turns proteins yellow
• Phosphoric Acid (H3PO4)• Used in fertilizers, animal
feed, soda, detergents• Hydrochloric Acid (HCl)
• “stomach acid”• Used in steel making &
food processing• Acetic Acid (HC2H3O2)
• “vinegar”• Used in food industry,
fungicides, plastics
COMMON BASES
• Sodium Hydroxide(NaOH)• “lye”• Drain cleaner, oven
cleaner, soap making• Potassium Hydroxide
(KOH)• Liquid soap, potash
• Magnesium Hydroxide(Mg(OH)2)• antacids
• Calcium Hydroxide(Ca(OH)2)• Slaked lime
• Ammonia Water (NH3)• Cleaning products
Strengths of Acids and Bases Video
PROPERTIES OF ACIDS
• Molecular compounds• Ionize in water H3O+1
• Corrosive to metals and skin (React with most metals to form hydrogen gas.)
• Taste sour (like lemons—citric acid) • pH less than 7 • Neutralizes bases producing salt and water • Electrolytes
PROPERTIES OF BASES
• Ionize in water OH-1
• Feel "slippery".• Taste bitter (like soap) • Electrolytes• Caustic• pH greater than 7. • Neutralizes acids producing a salt and
water.
SOME ACID/BASE INDICATORS
Acids:1. Blue litmus turns red2. Bromothymol blue turns yellow3. Phenolphthalein turns colorless/cloudy
Bases:1. Red litmus to blue2. Bromothymol blue turns blue3. Phenolphthalein turns hot pink
Can you tell which is which?
Sample drops here
PHENOLPTHALEIN
@ Wikimedia Commons, Public Domain
WHY ARE ACIDS & BASES ELECTROLYTES?
BECAUSE THEY PRODUCE IONS IN SOLUT ION
ACIDS AND BASES
IONIZATION EQUATIONS
• Acids• HBr(aq) + H2O(l) → H3O+(aq) + Br-(aq)
• Bases• NH3(aq) + H2O(l) → NH4
+(aq) + OH-(aq)
• Concentration: Amount of acid or base/amount of water or solution
• Strength: How well that particular acid or base ionizes (amount of H3O+1 or OH- )
• Strong acid/base: An acid/base that ionizes almost completely
• Weak acid/base: An acid/base that only partially ionizes
STRENGTH VS. CONCENTRATION
Strength of Acids and Bases Simulation
Strong WeakHCl H2SO4 HF CH3COOHHBr HClO3 H2S H2SO3HI HClO4 HNO2 H3PO4HNO3
LIST OF STRONG AND WEAK ACIDS
Organic acids: end in –COOH, weak acid
Ex: vinegar CH3COOH
Mem
oriz
e!!
Strong WeakGroup I and II metals with hydroxides
NH3 and any non-group I or II hydroxide
LIST OF STRONG AND WEAK BASES
TYPES OF ACIDS/BASESARRHENIUS & BRONSTED-LOWERY
ACID/BASE TYPE DEPENDS ON BEHAVIOR
Acid Behavior Base Behavior
Arrhenius Releases H+ in solution
Releases OH- in solution
Bronsted-Lowery Proton (H+) donor Proton (H+) acceptor
ARRHENIUS ACIDS/BASES
What happens when an Arrhenius acid and an Arrhenius base are mixed?
Acid produces H+Base produces OH-
Neutralization: H+(aq) + OH-
(aq) H2O(l)
General Equation: Acid + Base → Salt + Water
LiOH(aq) + HBr(aq) → LiBr(aq) + H2O(l)
What’s a salt? ionic compound formed from cation of a base (parent) & anion of an acid (parent)
ARRHENIUS ACIDS/BASES
Do neutralization reactions look familiar?
LiOH(aq) + HBr(aq) → LiBr(aq) + H2O(l)
Complete Ionic Eqn:
Net Ionic Eqn:
WRITE BALANCED EQNS FOR THE NEUTRALIZATION OF EACH OF THE
FOLLOWING A/B PAIRS:
• sodium hydroxide & hydrochloric acid
• calcium hydroxide & sulfuric acid
• potassium hydroxide & nitric acid
BRONSTED-LOWERY THEORY
During a Bronsted-Lowery acid/base reaction:
H+ is transferred from an acid to a base
HCl + NH3 → NH4+ + Cl-
Proton donor
Proton acceptor
VOCABULARY
• Monoprotic acid = only one ionizable H+
• Examples: HCl, HBr, HC2H3O2, HNO3
• Polyprotic acid = more than one ionizable H+
• Examples: H2SO4, H3PO4
• Amphoteric = substance that can act as an acid or a base• Example:• H2O + HCl → H3O+ + Cl-
• H2O + NH3 → NH4+ + OH-
BRONSTED-LOWERY CONJUGATE ACIDS & BASE
DEFINITIONS
• Conjugate Acid: formed when a Bronsted-Lowery base gains a H+
• Conjugate Base: formed when a Bronsted-Lowery acid loses a H+
HCl + NH3 → NH4+ + Cl-
Proton donor
Proton acceptor
conjugateacid
conjugate base
IDENTIFY A, B, CA, & CB
• NH3 + H3O+ → NH4+ + H2O
• CH3OH + NH2- → CH3O- + NH3
• OH- + H3O+ → H2O + H2O
• NH2- + H2O → NH3 + OH-
WRITE THE CONJUGATE BASE FOR EACH ACID BELOW.
• H3O+
• H2SO3
• HCO3-
• HOCl
• NH4+
WRITE THE CONJUGATE ACID FOR EACH BASE BELOW.
• I-
• SO3-2
• PO4-3
• C2H3O2-
• H2BO3-
WHICH IS STRONGER, PARENT ACID/BASE OR CONJUGATE?
PARENT ACID/BASE
• Pure water ionize slightly according to:
The product of molar concentrations of the ions is equal to a constant Kw.
= Kw
Kw = 1.00 * 10-14
AUTOIONIZATION OF WATER
11322
−+ +↔+ OHOHOHOH
][][ 113
−+ • OHOH
In a neutral solution:
In an acidic solution:
In a basic solution:
RELATIONSHIPS
7113 10*1][][ −−+ == OHOH
][][ 113
−+ > OHOH
][][ 113
−+ < OHOH
EXAMPLE PROBLEM
• What is the [OH-] in an aqueous solution if [H3O+] = 6.5 x 10-10 M?
pH and pOH Scales
[H+] M [OH-] M pH value
Acidic >1.0x10-7 <1.0X10-7 <7.00
Neutral =1.0x10-7 =1.0x10-7 =7.00
Basic <1.0x10-7 >1.0x10-7 >7.00
• A change in [H+] by a factor of 10 causes the pH to change by 1.
• Solution with a pH of 6 has 10x the [H+] as a solution with a pH of 7.
pH: measure of [H3O+1] in a solution, measure of “acidity”
pOH: measure of [OH-1] in a solution, measure of “alkalinity”
PH AND POH
Neutral0 7 14
Acid Base
Neutral0 7 14
Base Acid
1 42 53 6
IMPORTANT FORMULAS
]log[ 3+−= OHpH ]log[ 1−−= OHpOH
pHOH −+ = 10][ 3pOHOH −− = 10][ 1
14=+ pOHpH ]][[ 3−+= OHOHKW
PRACTICE PROBLEMS[H+] [OH-] pH pOH Soln Type
1.00 x 10-3 M
2.523
3.043.45 x 10-8 M
6.9 x 10-14 M
10.000
9.7
[H3O+1] =
FIND THE PH OF THE FOLLOWING:
a. 1.00 * 10-3 M d. 7.01 * 10-6 Mb. 1.00 * 10-6 M e. 9.47 * 10-8 Mc. 6.59 * 10-10 M f. 6.89 * 10-14 M
a. d.b. e.c. f.
pH =
FIND THE [H3O+1]
a. 3.000 d. 2.523b. 10.000 e. 6.149c. 6.607 f. 7.662
a. d.b. e.c. f.
pOH =
FIND THE PH FOR THE FOLLOWING:
a. 2.00 d. 4.976b. 7.00 e. 9.714c. 1.263 f. 3.004
a. d.b. e.c. f.
[OH-1] =
FIND THE PH FOR THE FOLLOWING:
a. 1.00 x 10-4 M d. 3.45 x 10-8 Mb. 1.00 x 10-6 M e. 4.97 x 10-10 Mc. 2.64 x 10-13 M f. 2.93 x 10-2 M
a. d.b. e.c. f.
FIND THE [H3O+1]
a. 1.00 * 10-4 M d. 3.45 * 10-8 Mb. 1.00 * 10-6 M e. 4.97 * 10-10 Mc. 2.64 * 10-13 M f. 2.93 * 10-2 M
a. d.b. e.c. f.
[OH-1] =
TITRATIONS
• An acid-base titration is a lab procedure used to determine the concentration of a solution by neutralizing it with a solution of known concentration.
• The moles of acid will equal the moles of base at the equivalencepoint.
Titration Technique Video
TITRATIONS
• Endpoint: When you actually stop doing the titration. This is determined by a color change in the indicator or an indication from a pH probe.
• Equivalence point: When the solution is neutralized& moles of H3O+ = molesOH-
• Indicator: weak acid or base and its conjugate ion, whose color changes with changes in pH
• Standard solution: solution of known concentration used as the titrant in a titration
TITRATION TERMS
TITRATION CURVES
On the following slide you will see 3 different curves.
The relationships are:Strong Acid titrated with Strong BaseWeak Acid titrated with Strong BaseStrong Acid titrated with Weak Base
Using those graphs compare the pH values of each substance as well as the equivalence points
TITRATION CURVES
TITRATION CURVES – WEAK ACID/STRONG BASE
TITRATION CURVES – WEAK BASE/STRONG ACID
DIPROTIC ACID TITRATION CURVE
BUFFERS
• Definition: weak acid/base & conjugate system that maintains pH when strong acid or base is added to the buffer• Example: Blood buffer HCO3
-/CO3-2
• How would a buffer affect the titration of an acid or base?• Much more titrant has to be added before
the pH changes significantly
BUFFERED TITRATION CURVE
TITRATIONS – EXAMPLE PROBLEMS
If 20.0 mL of 0.500 M NaOH to neutralize 25.0 mL of HCl, what is the concentration of the HCl?
If 27.4 mL of 0.0154 M Ba(OH)2 is used to titrate 20.0 mL of HCl, what is the concentration of HCl?
PRACTICE PROBLEM 1
How many milliliters of 0.0947 M NaOH are needed to neutralize 21.4 mL of 0.106 M HCl?
PRACTICE PROBLEM 2
If 26.4 mL of LiOH solution are required to neutralize 21.7 mL of 0.5M HBr, what is the concentration of the basic solution?
PRACTICE PROBLEM 3
What is the molar concentration of a 50.0 mL solution of NaOH that is titrated to an endpoint with 15.0 mL of a 0.00300 M solution of H2SO4?
PRACTICE PROBLEM 4
DILUTING SOLUTIONS
H2O12M
2M
Mole 1 = Mole 2
M=mol/volume ; mol= (M)(V)
(M1)(V1)=(M2)(V2) Key words – to dilute, diluted solution
DILUTING SOLUTIONS – PRACTICE PROBLEM
• What volume of 2.00M CaCl2 would you use to make 0.5L of 0.300M CaCl2?
STUDY TOPIC LIST
• Vocabulary/Definitions• Strong vs. Weak acids & bases• Acid/Base Properties• Uses of acids and bases• Nomenclature• Conjugate acids/bases• Neutralization reactions• pH/pOH/[H+]/[OH-]/Kw calculations• pH scale• Titration problems• Color changes of indicators (red & blue litmus paper,
phenolphthalein, bromothymol blue)• Titration curves• Buffers• Dilution problems• Arrhenius vs. Bronsted Lowery acid/base theories• Unit 8 Solutions material