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AcidsLesson 5
Acid Rain & Hydrolysis
Acid Rain
Acid Rain is caused by acid anhydrides
NO2 N2O4 automobile pollution
coal & smelter pollutionSO3SO2
SO3 + H2O → H2SO4(aq) Rain
Acid Rain has pH < 5
Normal Rain has pH = 6 due to dissolved CO2
CO2 + H2O → H2CO3
Acid rain dissolves metal, limestone, concrete structures.
Acid rain decreases the pH of lakes and causes toxic metals to leach into them.
Hydrolysis of Salts
HCl → NaCl + HOH
strong acid strong base neutral salt
When the acid and base parents are both strong the salt is always neutral.
NaCl Consider the acid and base that makes NaCl
1. Neutral Salts
+ NaOH
→ Na+ + Cl-
A neutral salt will dissociate in water
Cross off ions from strong parents that are neutral.
NaCl
Cross off all bold ions- they do not hydrolyze and are neutral
Neutral
Acidic
Cross off all bold ions- they do not hydrolyze and are neutral
Remaining amphriprotic ions are acidic
Neutral
Acidic
Basic
→ Na+ + Cl-
A neutral salt will dissociate in water
no ions to hydrolyze- neutral
Cross off ions from strong parents that are neutral.
NaCl
Hydrolysis of Salts
→ NaCN + HOHHCN
weak acid strong base basic salt
Consider NaCN Consider the acid and base that makes NaCN
+ NaOH
2. Basic Salts
basic
→ Na+ + CN-
A basic salt will first dissociate in water
CN- ⇄ HCN + OH-
Hydrolysis
neutral base- negative ions are bases
NaCN
+ H2O
Hydrolysis of Salts 3. Acidic Salts
→ NH4Cl HCl
strong acid weak base acid salt
NH4Cl
+ NH3
NH3 is a weak base
NH4Cl → NH4+ + Cl- positive ion- acid
neutralacid
NH4+ ⇄ H3O+
Hydrolysis
+ NH3+ H2O
4. Acidic Salts
acid saltweak basestrong acid
→ FeCl3 + 3HOH 3HCl
FeCl3
+ Fe(OH)3
Fe3+
OH-
H2O
H2O
H2O
H2O
H2O
H2O
Fe3+
OH-
H2O
H2O
H2O
H2O
H2O
Hydronium ion
FeCl3
Fe(H2O)63+ ⇄ H+ + Fe(H2O)5(OH)2+
positive ion - acid
Hydrolysis- when the positive or negative ion in a salt reacts with water as an acid or base.
Look for the reaction on the acid chart!
→ Fe3+ + 3Cl-
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