Chapter 14 Acids and Bases -...
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Chapter 14 Acids and Bases
Transcript of Chapter 14 Acids and Bases -...
Chapter 14 Acids and Bases
General Properties of Acids
1. An acid tastes sour - acidus = Latin, sour; acetum= Latin, vinegar
2. An acid turns indicator dye litmus from blue to red.
3. An acid reacts with certain metals (Fe, Sn, Zn, Mg).
4. An acid is an electrolyte.
5. An acid reacts with bases to form salts and water
1. HNO2 is named
A) hydronitric acid. B) hydronitrous acid. C) nitric acid. D) nitrous acid. E) hydrogen nitrite.
NO3- = nitrate
NO2- = nitrite
Common AcidsName Formula Uses Strength
Perchloric HClO4 explosives, catalysts Strong
Nitric HNO3 explosives, fertilizers, dyes, glues Strong
Sulfuric H2SO4explosives, fertilizers, dyes, glue,
batteries Strong
Hydrochloric HCl metal cleaning, food prep, ore refining, stomach acid
Strong
Phosphoric H3PO4fertilizers, plastics, food
preservation Moderate
Chloric HClO3 explosives Moderate
Acetic HC2H3O2plastics, food preservation,
vinegarWeak
Hydrofluoric HF metal cleaning, glass etching Weak
Carbonic H2CO3 soda water, blood buffer Weak
Hypochlorous HClO sanitizer Weak
Boric H3BO3 eye wash Weak
Sources of Acids
SO3 + H2O ----------> H2SO4 Sulfuric Acid
NO2 + H2O ----------> HNO3 Nitric Acid
CO2 + H2O ----------> H2CO3 Carbonic Acid
2 NaCl + H2SO4 ----------> Na2SO4 + 2 HCl Hydrochloric Acid
General Properties of Bases
1. A base tastes bitter
2. A base turns indicator dye litmus from red to blue.
3. A base feels slippery or soapy when mixed with a small amount of water
4. A base reacts with acids to form salts and water
2. What is the chemical formula for the base calcium hydroxide?
A) CaOH B) CaH C) CaH2 D) Ca(OH)2 E) Ca2(OH)
Ca2+
OH-
Name Formula Common Name Uses Strength
Sodium Hydroxide NaOH Lye, Caustic Soda
soap, plastic production, petroleum refining Strong
Potassium Hydroxide KOH Caustic Potash
soap, cotton processing, electroplating Strong
Calcium Hydroxide
Ca(OH)2 Slaked Lime cement Strong
Sodium Bicarbonate
NaHCO3 Baking Soda food preparation, antacids Weak
Magnesium Hydroxide
Mg(OH)2 Milk of Magnesia antacids Weak
Ammonium Hydroxide
NH4OH Ammonia Waterfertilizers, detergents,
explosives Weak
Common Bases
Sources of Bases
CaO + H2O ----------> Ca(OH)2 Calcium hydroxide
Li2O + H2O ----------> 2 LiOH Lithium hydroxide
2 Na + 2 H2O ----------> 2 NaOH + H2 Sodium hydroxide
Ca + 2 H2O ----------> Ca(OH)2 + H2
Molecular Definitions of
Acids and Bases
Acids and Bases in Solution
Acids “ionize” in water to form H+ ions. (More precisely, the H+ from the acid molecule is donated
to a water molecule to form hydronium ion, H3O+)
Bases “dissociate” in water to form OH- ions. (Bases, such as NH3, that do not contain OH- ions,
produce OH- by pulling H+ off water molecules.)
In the reaction of an acid with a base, the H+ from the acid combines with the OH- from the base to make water.
The cation from the base combines with the anion from the acid to make a salt.
acid + base ➜ salt + water
Arrhenius Theory
3. Which of the following can act as an Arrhenius base?
A) Ca(OH)2 B) H2O C) KOH D) H2SO4 E) Two of the above
Brønsted-Lowry TheoryBrønsted-Lowry Acid-Base Reactions involve transfer
of protons.
A Brønsted-Lowry Acid is a proton donor.
A Brønsted-Lowry Base is a proton acceptor.
Brønsted-Lowry Theory
An acid-base reaction involves proton transfer:
H-A + [B:]- ——-> A:- + H-B
[H-A] + B: ——-> [A:]- + [H-B]+
[H-A:]- + B: ——-> [:A:]2- + [H-B]+
[H-A]+ + B: ——-> A: + [H-B]+
Brønsted-Lowry Acids
A Brønsted-Lowry Acid is a proton donor.
Any material with a H is a potential proton donor, but because of molecular structure, one or more protons are sometimes more
likely to be transferred.
Molecular Models of Selected Acids
4. Which of the following can act as a Brønsted–Lowry acid?
A) NH3 B) NaOH C) BF3 D) HBr E) Two of the above
Ionization of an Acid
The ionization of an acid in water is more accurately written as:
HCl + H2O ----------> Cl- + [H3O]+
proton donor
proton acceptor
chloride ion
hydronium ion
- +
Ionization of an Acid
Brønsted-Lowry Bases
A Brønsted-Lowry Base is a proton acceptor.
Any material with a lone pair of electrons is a potential proton acceptor, but because of
molecular structure, one or more atoms with lone pairs may be more likely to accept a
proton.
Bronsted Lowry Acid Base Reaction
Conjugate Pairs 1. In a Brønsted-Lowry reaction, the original base becomes an acid in the reverse reaction, and the original acid becomes a base in the reverse process
2. Each reactant and product are a conjugate pair.
3. The original base becomes a conjugate acid, and the original acid becomes a conjugate base
H-A + :B ⇔ :A- + H-B+
acid base conjugate conjugate base acid
HCHO2 + H2O ⇔ CHO2- + H3O+
acid base conjugate conjugate base acid
H2O + NH3: ⇔ HO- + NH4+
acid base conjugate conjugate base acid
Conjugate Acid Base Pairs
Conjugate Pairs
H2O and OH- are an acid/base conjugate
pair.
NH3 and NH4+ are an base/acid conjugate
pair.
5. Identify the two Brønsted–Lowry acids in the following reaction:
H3PO4 + NH3 ⇄ NH4+ + H2PO4–
A) H3PO4 and NH3 B) H3PO4 and NH4+
C) H3PO4 and H2PO4–
D) NH3 and NH4+
E) NH3 and H2PO4–
6. What is the conjugate acid of H2C6H5O6– ?
A) C6H5O63–
B) HC6H5O62– C) H2C6H5O6– D) H3C6H5O6 E) H4C6H5O6+
Lewis Acids and Bases
electron pair donor = Lewis Base = nucleophile
electron pair acceptor = Lewis Acid = electrophile
Lewis acid-base reactions include all the previously described acid-base reactions plus
additional types.
Molecules as Lewis Acids and Bases
- +
The reaction of the Lewis acid BF3 with the Lewis base NH3
Reactions of
Acids and Bases
Acid-Base Reactions
Also called neutralization reactions because the acid and base neutralize each other’s properties
2 HNO3(aq) + Ca(OH)2(aq) ➜ Ca(NO3)2(aq) + 2 H2O(l)
Note that the cation from the base combines with the anion from the acid to make the water soluble salt.
H+(aq) + OH-(aq) ➜ H2O(l)
(as long as the salt that forms is soluble in water)
The net ionic equation for an acid-base reaction is
Neutralization - The reaction of an acid and a base
HCl + NaOH ----------> NaCl + H2O
7. What is the salt formed in the neutralization reaction between nitric acid and potassium hydroxide?
A) KCl B) KNO2
C) KNO3
D) H2O
E) KH
HNO3 (aq) + KOH (aq)→ KNO3 (aq) + H2O (l)
Other Useful Acid-Base Reactions
1. Mg(OH)2 + 2 HCl ----------> 4 H2O + MgCl2
2. CaCO3 + H2SO4 ----------> H2O + CO2 + CaSO4
3. NaHCO3 + RCOOH ----------> H2O + CO2 + RCOO-Na+
Titrations
A specific volume of the solution to be titrated is added to a flask.
An indicator is added.
A titrant (OF KNOWN C O N C E N T R A T I O N ) i s added to the solution being titrated until the indicator changes colore.
The volume of titrant added from the buret is measured. THE CONCENTRATION OF THE ORIGINAL SOLUTION IS THEN DETERMINED BY CALCULATION.
8. A 25.0 mL solution of 3.00 M hydrochloric acid requires 65.6 mL of NaOH solution to reach the endpoint. Calculate the original concentration of the NaOH.A) 1.14 M B) 0.381 M
C) 0.257 M
D) 3.00 M
E) 3.43 M
HCl (aq) + NaOH (aq)→ NaCl (aq) + H2O (l)
How many moles of HCl reacted? How many moles of NaOH reacted? In what volume was the NaOH contained? What is the molarity of the NaOH solution?
0.0250 L HCl solution X X3.00 mol HCl
1.00 L HCl solution1.00 mol NaOH1.00 mol HCl
= 0.0750 mol NaOH
0.0750 mol NaOH0.0656 L NaOH solution
= 1.14 M NaOHM = mol/L =
9. A 25.0 mL solution of 3.00 M phosphoric acid requires 65.6 mL of NaOH solution to reach the endpoint. Calculate the original concentration of the NaOH.
A) 1.14 M B) 0.381 M
C) 0.257 M
D) 3.00 M
E) 3.43 M
H3PO4 (aq) + 3 NaOH (aq)→ Na3PO4 (aq) + 3 H2O (l)
How many moles of H3PO4 reacted? How many moles of NaOH reacted? In what volume was the NaOH contained? What is the molarity of the NaOH solution?
0.0250 L H3PO4 solution X X3.00 mol H3PO4
1.00 L H3PO4 solution3.00 mol NaOH1.00 mol H3PO4
= 0.225 mol NaOH
0.225 mol NaOH0.0656 L NaOH solution = 3.43 M NaOHM = mol/L =
✔
Why not use M1V1 = M2V2 for titrations ??
0.0250 L HCl solution X X3.00 mol HCl
1.00 L HCl solution1.00 mol NaOH1.00 mol HCl
= 0.0750 mol NaOH
HCl (aq) + NaOH (aq)→ NaCl (aq) + H2O (l)
H3PO4 (aq) + 3 NaOH (aq)→ Na3PO4 (aq) + 3 H2O (l)
0.0250 L H3PO4 solution X X3.00 mol H3PO4
1.00 L H3PO4 solution3.00 mol NaOH1.00 mol H3PO4
= 0.225 mol NaOH
10. What volume of a 0.4590 M NaOH solution is required to reach the endpoint in the titration of 25.00 mL sample of 0.3669 M H2SO4?A) 39.97 mL B) 31.28 mL
C) 26.66 mL
D) 19.98 mL E) 25.00 mL
H2SO4 (aq) + 2 NaOH (aq)→ Na2SO4 (aq) + 2 H2O (l)
How many moles of H2SO4 reacted? How many moles of NaOH reacted? What volume of NaOH was needed?
0.02500 L H2SO4 solution X X0.3669 mol H2SO4
1.00 L H2SO4 solution2.00 mol NaOH1.00 mol H2SO4
= 0.01834 mol NaOH
= 0.03997 L NaOH solution0.01834 mol NaOH X1.00 L NaOH solution
0.4590 mol NaOH
mol compound A
L solution A
mol compound B
L solution B
2 NaOH (aq) + H2SO4 (aq) → Na2SO4 (aq) + 2 H2O (l)
M M
mol/mol ratio
Moles of A
Moles of B
Grams of A
Grams of B
Particles of A
Particles of B
Avogadro’s Number Avogadro’s Number
Molar MassMolar Mass
Coefficients
Liters of a Solution of A
Liters of a Solution of B
MolarityMolarity
The Big Picture of Stoichiometry
