Download Ch06 BalancingChemRxns

Writing Chemical Equations
to Symbolize Chemical Reactions
Chapter
6&7
1
Solid aluminum metal reacts with oxygen gas to
produce solid aluminum oxide.
1. Write the formulas of the reactants and products.
•
Al + O2 → Al2O3
2. Add symbols to indicate physical state.
•
Al(s) + O2(g) → Al2O3(s)
3. Balance (Law of Conservation of Mass)
•
4Al(s) + 3O2(g) → 2Al2O3(s)
4. Synthesis Reaction
2
Electrical current through water.
Electrolysis of water into its elements.
1. Write the skeleton equation
•
H2O → H2 + O2
2. Put in physical state symbols
•
H2O(L) → H2(g) + O2(g)
3. Balance
2 H2O(L) → 2 H2(g) + O2(g)
4. Decomposition
•
3
Solid iron rusts. Solid iron reacts with oxygen gas to
produce iron(III) oxide.
1. Write the skeleton equation
•
Fe + O2 → Fe2O3
2. Put in physical state symbols
•
Fe(s) + O2(g) → Fe2O3(s)
3. Balance
•
4 Fe(s) + 3 O2(g) → 2 Fe2O3(s)
4. Synthesis (aka combination)
4
Ammonium Nitrate dissolves.
Since we have defined dissolving as a physical change, this is
NOT a chemical reaction, just a physical change.
1. Write the skeleton equation
• NH4NO3 → NH4+ + NO3−
2. Put in physical state symbols
+
−
• NH4NO3(s) → NH4 (aq) + NO3 (aq)
3. Balance
• Already balanced.
4. Dissolving
5
Aqueous sodium dichromate is reacted with aqueous lead(II) nitrate to
produce a solid precipitate of lead(II) dichromate and aqueous sodium
nitrate.
1. Write the skeleton equation
Na2Cr2O7 + Pb(NO3)2 → PbCr2O7 + NaNO3
2. Put in physical state symbols
Na2Cr2O7(aq) + Pb(NO3)2(aq) → PbCr2O7(ppt) + NaNO3(aq)
3. Balance
Na2Cr2O7(aq) + Pb(NO3)2(aq) → PbCr2O7(ppt) + 2NaNO3(aq)
4. Double Replacement
6
Solid potassium metal is reacted with water to produce
aqueous potassium hydroxide and hydrogen gas.
1. Write the skeleton equation
•
K + H2O → KOH + H2
2. Put in physical state symbols
•
K(s) + H2O(L) → KOH(aq) + H2(g)
3. Balance
•
2K(s) + 2H2O(L) → 2KOH(aq) + H2(g)
4. Single Replacement
7
Solid calcium reacted with liquid water to produce aqueous
calcium hydroxide and hydrogen gas.
1. Write the skeleton equation
•
Ca + H2O → Ca(OH)2 + H2
2. Put in physical state symbols
•
Ca(s) + H2O(L) → Ca(OH)2(aq) + H2(g)
3. Balance
•
Ca(s) + 2H2O(L) → Ca(OH)2(aq) + H2(g)
4. Single Replacement
8
Solid zinc reacts with aqueous hydrochloric acid to produce
aqueous zinc chloride and hydrogen gas.
1. Write the skeleton equation
• Zn + HCl → ZnCl2 + H2
2. Put in physical state symbols
• Zn(s) + HCl(aq) → ZnCl2(aq) + H2(g)
3. Balance
• Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
4. Single Replacement
9
Burning of methane gas, CH4
1. Write the skeleton equation
•
CH4 + O2 → H2O + CO2
2. Put in physical state symbols
•
CH4(g) + O2(g) → H2O(g) + CO2(g)
3. Balance
•
CH4 (g) + 2O2(g) → 2H2O(g) + CO2(g)
4. This is the gas that comes through our Bunsen
burners.
5. Combustion
10
Nylon is formed from hexamethylenedamine reacting with
sebacoyl chloride to produce the nylon polymer and
hydrochloric acid.
1. Nylon is a generic term to represent a
particular type of polymer.
•
C6H12N2H6 + C6H8Cl2O2 → C12H20O2N2H4 + 2 HCl
2. Balance
•
C6H12N2H6 + C6H8Cl2O2 → C12H20O2N2H4 + 2 HCl
3. This is a typical polymerization
reaction.
•
•
Polymer = many mers (repeating small units)
Polymerization = making polymers from
monomers.
11
Polymerization - making large molecules from
small units
1. You may remember
that many glucose
molecules hooked
together make the
polymer starch or
cellulose
12