chemical equations. i. writing chemical equations a. reactantsproducts b. balancing chemical...
TRANSCRIPT
Chemical Equations
I. Writing Chemical Equations A.
Reactants Products
B. Balancing chemical equations
1) Numbers are written in front of each molecule so that there are the same number of each atom on both sides…these numbers are called coefficients
H2 + O2 H2O
H2 + O2 H2 O
2) It doesn’t matter which atom you decide to balance first
3) DO NOT change ANY subscripts
4) Subscript x coefficient = # of that atom
2 22 2
5) Recheck everything before you quit the problem
Try balancing these:
a) SO2 + O2 => SO322
b) Fe2O3 + H2 => Fe + H2O 323
c) C2H6 + O2 => CO2 + H2O 2 3
d) Aluminum carbonate + hydrochloric acid => aluminum chloride + carbonic acid
72
4 C2H6 + O2 => CO2 + H2O 672
d) Aluminum carbonate + hydrochloric acid => aluminum chloride + carbonic acid
II.Five basic Types of Chemical Reactions
1)Synthesis (composition)
2) Decomposition
3) Single Replacement
4) Double Replacement
5) Combustion
Before we begin …….
There are 7 elements that MUST be written with a subscript of 2 whenever they are by themselves in an equation:
I2
Br2
Cl2F2
O2
N2 H2
I
BringClayForOur
NewHouse
Br I N Cl H O F
1) Synthesis (composition)
* Template: A + X => AX
Clue 1: Only ONE product is formed
Clue 2 : Two elements as reactants
Clue 3 : metal oxide + water => metal hydroxide
Clue 4: non metal oxide + water => acid
Template: A + X => AX
Clue 1: Only ONE product is formed
Clue 2: Two elements as reactants
Examples:
2 Na + Cl2 => 2 NaCl
2 H2 + O2 => 2 H2O
1) Synthesis (composition)
Template: A + X => AX
Clue 3: metal oxide + water => metal hydroxide
Examples:
Na2O + H2O => 2 NaOH
calcium oxide + water => ???
CaO + H2O => Ca(OH)2
1) Synthesis (composition)
Template: A + X => AX
Clue 4: non metal oxide + water => acid
Examples:
CO2 + H2O => H2CO3
sulfur trioxide + water => ?????
SO3 + H2O => H2SO4
1) Synthesis (composition)
Practice:
a) K2O + H2O =>
b) N2O5 + H2O =>
c) Sodium is added to chlorine gas
d) Lithium oxide is added to water
1) Synthesis (composition)
* Template: AX => A + X Clue 1: metal chlorates => metal chloride + oxygen
Examples:
KClO3 => KCl + O2
barium chlorate => ??? + ???
Ba(ClO3)2 => BaCl2 + O2
(oxygen is proven by the glowing splint test)
2) Decomposition Reaction
2 2 3
3
Template: AX => A + X
Clue 2:
metal carbonates => metal oxide + carbon dioxide
CaCO3=> ??? + ???
CaCO3=> CaO+ CO2
(CO2 is proven by the flaming splint test)
2) Decomposition Reaction
Template: AX => A + X
Clue 3:
metal hydroxides=> metal oxide + water
Example:
Ca(OH)2 => CaO + H2O
2) Decomposition Reaction
Template: AX => A + X
Clue 4:
Two elements => separate elements
2 H2O => 2 H2 + O2
2 HgO => 2 Hg + O2
2) Decomposition Reaction
Template: A + BX => AX + B
AX + Y => AY + X
Clue 1: free metal replaces the “front”
element in a compound
Fe + CuSO4 => FeSO4 + Cu
Na + HOH => NaOH + H2
(metals replace the “front” element)
3) Single Replacement
2 2 2
2 Na + 2 HOH => 2NaOH + H2
(note how water is written)
NOT….
2 Na + H2O => Na2O + H2
ALERT!!!!!!
Template: A + BX => AX + B
AX + Y => AY + X
Clue 2: free non metal replaces the non
metal in a compound
Example:
Cl2 + NaBr => NaCl + Br2
3) Single Replacement
2 2
Template: AX + BY => AY + BX
Clue 1: two compounds are reacting
Examples:
AgNO3 + NaCl => AgCl + NaNO3
(switch the “front” elements)
lead (II) acetate is added to sodium iodide
Pb(C2H3O2)2 + 2NaI => PbI2 + 2NaC2H3O2
4) Double Replacement
Template: AX + BY => AY + BX
Clue 2: Double replacement reactions
always form one of these:
- a gas
- water
- a precipitate (something not soluble)
4) Double Replacement
Predicting what precipitate forms:
4) Double Replacement
COMPOUNDS SOLUBILITY
Alkali metals and ammonia Always soluble
Nitrates, chlorates, acetates Always soluble
Sulfates Soluble except with Ag+, Pb+2, Ba+2, Sr+2, Ca+2
Chlorides, Bromides, Iodides, Soluble except with Ag+, Pb+2, Hg+1
Carbonates, Phosphates, Hydroxides, Chromates, Sulfides
Never Soluble except with alkali metals and ammonia
Are these soluble?LiClyesCuOH noAgCl no
(NH4)2SO4yes
Na2CO3yes
Template: AX + O2 => AO + BO
Clue 1: Statement includes “burning”
which means to add oxygen gas
Example:
CH4 + 2 O2 => CO2 + 2 H2O
5) Combustion Reactions