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