Section 4.4 Chemical Reactions Quiz 1
Types of Chemical
ReactionsProblems…..
Common
Writing AP Equations for a Happier Life
While AP no longer has an equation writing section embedded in the test, understanding what reaction
will occur is assumed throughout the content. The best way to prepare for this is to practice lots of
equations. These equations will need to be balanced and written in net ionic form. All spectator ions
must be left out and all ions must be written with correct charges. All molecular substances and nonsoluble compounds must be written together (not ionized!). Weak electrolytes, such as acetic acid, are
not ionized. Solids, gases and pure liquids are written together also.
Equations are generally one of a limited number of types, the first challenge is to determine that type….
#1 Issue – Writing Reactants & Products in Proper Form
Solids,
Section
4.4 gases and pure liquids are written
Types of Chemical Reactions
together……




Solid lithium dioxide (#2) – Li2O(s)
Solid calcium fluoride (#3) - CaF2(s)
Carbon disulfide vapor (#4) - CS2(g)
Potassium Chloride (#10) - KCl(s)
(No water, not in solution)
 Weak Acids
- HF(l) (#3)
- HNO2(l) (#9)
- (l) = (aq); (l) LIQUIDS = (aq) IONS in solution
Weak4.4
electrolytes, such as acetic acid, are not
Section
Types of Chemical
ionized Reactions
(but strong acids are)……
 Weak Acids are not ionized
- HF(l) (#3)
- HNO2(l) (#9)
 Strong Acids and Bases ARE ionized
- Na+(aq) + OH-(aq) - Sodium hydroxide (#6)
- 2H+(aq) + SO42- (aq) – Sulfuric Acid (#3)
 Compounds that might be strong electrolytes are
still solid if there is no water…. - (#10) - KCl(s)
Section
4.4
All spectator
ions must be left out and all ions written
correct charges….
Types of Chemicalwith
Reactions
 Spectator ions
- Are IONS (in solution) at the beginning and end
- Do not react (they “watch” or “spectate”)
 Look for ions that are usually soluble (e.g. sodium,
potassium, chloride, nitrate, sulfate)
- SO42- (aq) (#3)
- Na+(aq) & NO3-(aq) (#5)
- Cl-(aq) (#7)
Section 4.4
Types of ChemicalAnhydrides
Reactions (#2 & #9)
 Anhydride means “without water”. Water is a reactant, and
there is NO oxidation state change (i.e. not redox)
 Metal oxide (basic anhydrides) plus water yields bases (#2)
- Solid lithium oxide is added to excess water
- Li2O(s) + H2O(l)  2Li+(aq) + 2OH-(aq)
 Non-metal oxides (acid anhydrides) plus water yields acids (#9)
- Dinitrogen trioxide gas is bubbled into water.
- N2O3(g) + H2O(l)  2HNO2(l)
 Metallic hydrides, phosphorous halides and group I & II nitrides
on later problems
Section 4.4
Metals (#6 & #7)
Types of(free
Chemical
Reactions
metals
are strong reducers….)
 Strongly reducing metals (Li, K, Ba, Ca, Na) react with water to
form metal ions, hydroxide and hydrogen (#6)
- Sodium metal is added to water.
- 2Na(s) + 2H2O(l)  2Na+(aq) + 2OH-(aq) + H2(g)
- Note – CHARGES must balance (because it is a redox equation)…
 Active metals replace less active metals (or hydrogen) (#7)
- Magnesium turnings are added to a solution of iron (III) chloride
- 3Mg(s) + 2Fe3+(aq)  3Mg2+(aq) + 2Fe(s)
- Note – CHARGES must balance (because it is a redox equation)…
Section 4.4
Types of Chemical Reactions
Section 4.4
Other stuff…..
Types of Chemical Reactions
 Redox: Oxidation and reduction BOTH occur…..
- Magnesium turnings are added to a solution of iron (III) chloride
- Mg(s) + 2Cl-(aq)  2MgCl2 has two problems:
- While Mg has oxidized, nothing has reduced
- Cl- is a spectator ion
 Metathesis: A conjugate base of a weak acid will attract
protons in solution (#3)
- Dilute sulfuric acid is added to solid calcium fluoride
- 2H+(aq) + CaF2(s)  2HF(l) + Ca2+(aq)
- Calcium was part of the solid, so it is NOT a spectator
- Sulfate is a spectator (CaSO4 is soluble)