1. Reactions involving Acids, Bases, & Salts
CHAPTER 10
Reactions involving
Acids, Bases, & Salts

2. Properties of Aqueous Solutions of Acids
Acidic properties
taste sour
change the colors of indicators
turn litmus red
react with metals to generate H2(g)
react with metal oxides and hydroxides to form salts and water
aqueous solutions conduct electricity

3. Properties of Aqueous Solutions of Bases
Basic properties
taste bitter
feel slippery
change colors of indicators
turn litmus blue
react with acids to form salts and water
aqueous solutions conduct electricity

4. Arrhenius Theory Svante Augustus Arrhenius - 1884
acids are anything that generate H+ in aqueous solutions, while bases produce OH- in aqueous solutions

5. Arrhenius Theory neutralization - combination of H+ (or H3O+) with OH-
strong acids - ionize 100% in water
HCl, HBr, HI, H2SO4, HNO3, HClO4, HClO3
strong bases - ionize 100% in water
LiOH, NaOH, KOH, RbOH, CsOH,
Ca(OH)2, Sr(OH)2, Ba(OH)2
Can also happen with weak acids and/or weak bases 5 6

6. Arrhenius Theory net ionic equation for strong acid with strong base
total ionic equation for strong acid with strong base
net ionic equation for strong acid with strong base 6 7

7. Bronsted-Lowry Acid-Base Theory
acids - proton (H+) donor
bases - proton (H+) acceptor 8 9

8. acid-base reactions are proton transfer reactions
note that we are often making coordinate covalent bonds
differences between Arrhenius & Bronsted-Lowry theories
reaction does not have to occur in an aqueous solution
bases do not have to be hydroxides ~ ammonia is not a hydroxide 9 10

9. Bronsted-Lowry Acid-Base Theory
weak acids have strong conjugate bases
weak bases have strong conjugate acids
primary reason they are weak acids or bases: strong conjugates recombine to form the original species
Water is water can be either an acid or base in Bronsted-Lowry theory
It is both amphiprotic and amphoteric
amphiprotic ~ can donate or accept a proton
amphoteric ~ a substance that can be either an acid or a base. 12 13

10. Amines amines are weak bases that behave like ammonia
amines have organic groups attached to -NH2 group 14 15

11. HF>>HCl>HBr>HI HF<<HCl<HBr<HI
Strengths of Acids
Binary Acids
acid strength increases with decreasing bond strength (inversely proportional)
Strongest bond = weakest acid
hydrogen halides
bond strength
HF>>HCl>HBr>HI
acid strength
HF<<HCl<HBr<HI 16 17

12. H2O>> H2S> H2Se> H2Te H2O<< H2S< H2Se< H2Te
Strengths of Acids
VIA hydrides
bond strength
H2O>> H2S> H2Se> H2Te
acid strength
H2O<< H2S< H2Se< H2Te 17 18

13. Strengths of Acids acid leveling
strongest acid that can exist in water is H3O+
acids that are stronger than H3O+ merely react with water to produce H3O+
consequently all strong soluble acids have the same strength in water
can only distinguish acid strength differences of strong acids in nonaqueous solutions like acetic acid

14. Strengths of Acids strongest acid in water is H3O+
HCl + H2O ® H3O+ + Cl-
HCl is so strong it forces water to accept H+
strongest base in water is OH-
NH2- + H2O ® NH3 + OH-
NH2- is strong enough to remove H+ from water
Why? Water is amphiprotic 21 22

15. Strengths of Acids Acid Conjugate Base Strongest acid Weakest base
HClO ClO4-
H+(H3O+) H2O
CH3CO2H « CH3CO2-
H2O OH-
NH NH2-
Weakest acid Strongest base 20 21

16. Strengths of Acids
ternary acids /oxyacids – acids containing H, O, and another element (usually a nonmetal)
ternary acid strength usually increases with
increasing number of O atoms on central atom
increasing oxidation state of central atom
acids having same central atom, highest oxidation state of central atom is usually strongest acid
HClO < HClO2 < HClO3 < HClO4
weakest strongest 24 25

17. HNO2<HNO3 H2SO3< H2SO4 HNO2>HNO3 H2SO3> H2SO4
Strengths of Acids
weak ternary acids have stronger H-O bonds than stronger ternary acids
acid strength
HNO2<HNO H2SO3< H2SO4
H-O bond strength
HNO2>HNO H2SO3> H2SO4 23 24

18. Lewis Acid-Base Theory
acid – an electron pair acceptor
base – an electron pair donor
neutralization - coordinate covalent bond formation 47 48

19. ~ ionization of ammonia
in more detail
~ ionization of HBr
HBr + H2O ® H3O+ + Br-
acid base
in more detail 48 49

20. Lewis Theory sodium fluoride + boron trifluoride ammonia + HBr
Lewis acid-base reaction but not Arrhenius or Bronsted-Lowry
NaF + BF3 ® Na+ + BF4-
ammonia + HBr
Lewis and Bronsted-Lowry acid base reaction but not Arrhenius
NH3 + HBr ® NH4+ + Br- 50 51

21. Acidic, Basic, and Neutral Salts
A salt is an ionic compound that contains at least one spectator ion. The salt therefore dissociates completely in water Neutral salts – normal salts: contain no ionizible H atoms or OH groups. These salts have no effect on the pH of a solution. Normally formed between the reaction of a strong acid and strong base. Most alkali and alkaline earth binaries are neutral salts. Ex. NaCl, KI, LiNO3, MgBr2

22. Some salts will produce an acidic or basic solution when added to water.
Acidic salts are ionic compounds that can provide an H+ to a solution; does not necessarily produce acidic solns. These compounds are able to neutralize bases. Normally formed from the reaction of a strong acid and weak base.
Ex. NH4I , KH2 AsO4, K2 HPO4, NaHSO4 , NaHCO3
NH4 I + H2O  H3O NH3 + I-

23. Basic salts are ionic compounds that increase the OH- concentration
Basic salts are ionic compounds that increase the OH- concentration. If the compound has an anion that would make a weak acid then it’s a basic salt. Can contain unreacted OH group that can neutralize acids even though they are not necessarily basic.
Most transition metal binary compounds in water make basic salts. Basic salts tend to be insoluble. Can also be formed from the reaction of a strong base and a weak acid.
Ex. Al(OH)2 Cl, Fe(OH)2 and some anions to look for F-, CN- , CNS- , H-
NaF + H2O  Na+ + OH- + HF
Li2C2O4 + H2O  H2C2O4 + Li+ + OH-

24. One method of increasing the solubility and the absorption of a medication is to convert weakly acidic drugs into sodium salts before making the pills that will be ingested. How does this preparation method enhance the drug’s solubility in the stomach? (hint: stomach acid is about 1M HCl)
Medicines that are weakly basic are not absorbed well into the bloodstream. One method to increase their absorption is to take an antacid at the same time that the medicine is administered. How does this method increase the absorption?