Chemical Equations

I. Writing Chemical Equations A. ReactantsProducts  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 H 2 + O 2  H 2 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 ) Recheck everything before you quit the problem

Try balancing these: a) SO 2 + O 2 => SO 3 22 b) Fe 2 O 3 + H 2 => Fe + H 2 O 32 3 c) C 2 H 6 + O 2 => CO 2 + H 2 O 23 d)Aluminum carbonate + hydrochloric acid => aluminum chloride + carbonic acid C 2 H 6 + O 2 => CO 2 + H 2 O 67 2

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: I2I2 Br 2 Cl 2 F2F2 O2O2 N2N2 H2H2 I Bring Clay For Our New House 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 + Cl 2 => 2 NaCl 2 H 2 + O 2 => 2 H 2 O 1) Synthesis (composition)

Template: A + X => AX Clue 3: metal oxide + water => metal hydroxide Examples: Na 2 O + H 2 O => 2 NaOH calcium oxide + water => ??? CaO + H 2 O => Ca(OH) 2 1) Synthesis (composition)

Template: A + X => AX Clue 4: non metal oxide + water => acid Examples: CO 2 + H 2 O => H 2 CO 3 sulfur trioxide + water => ????? SO 3 + H 2 O => H 2 SO 4 1) Synthesis (composition)

Practice: a) K 2 O + H 2 O => b) N 2 O 5 + H 2 O => 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: KClO 3 => KCl + O 2 barium chlorate => ??? + ??? Ba(ClO 3 ) 2 => BaCl 2 + O 2 (oxygen is proven by the glowing splint test) 2) Decomposition Reaction 223 3

Template: AX => A + X Clue 2: metal carbonates => metal oxide + carbon dioxide CaCO 3 => ??? + ??? CaCO 3 => CaO+ CO 2 (CO 2 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 + H 2 O 2) Decomposition Reaction

Template: AX => A + X Clue 4: Two elements => separate elements 2 H 2 O => 2 H 2 + O 2 2 HgO => 2 Hg + O 2 2) Decomposition Reaction

Template: A + BX => AX + B AX + Y => AY + X Clue 1: free metal replaces the “front” element in a compound Fe + CuSO 4 => FeSO 4 + Cu Na + HOH => NaOH + H 2 (metals replace the “front” element) 3) Single Replacement 222

2 Na + 2 HOH => 2NaOH + H 2 (note how water is written) NOT…. 2 Na + H 2 O => Na 2 O + H 2 ALERT!!!!!!

Template: A + BX => AX + B AX + Y => AY + X Clue 2: free non metal replaces the non metal in a compound Example: Cl 2 + NaBr => NaCl + Br 2 3) Single Replacement 2 2

Template: AX + BY => AY + BX Clue 1: two compounds are reacting Examples: AgNO 3 + NaCl => AgCl + NaNO 3 (switch the “front” elements) lead (II) acetate is added to sodium iodide Pb(C 2 H 3 O 2 ) 2 + 2NaI => PbI 2 + 2NaC 2 H 3 O 2 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 COMPOUNDSSOLUBILITY Alkali metals and ammoniaAlways soluble Nitrates, chlorates, acetatesAlways soluble SulfatesSoluble 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? LiCl yes CuOH no AgCl no (NH 4 ) 2 SO 4 yes Na 2 CO 3 yes

Template: AX + O 2 => AO + BO Clue 1: Statement includes “burning” which means to add oxygen gas Example: CH O 2 => CO H 2 O 5) Combustion Reactions