Synthesis (Combination) Reactions 1 or more substances combine to form a more complex one. General Formula A + B  AB 3 common types i. 2 elements combine ii. Oxide combines with H 2 O iii. 2 oxides combine forming a salt

i. 2 Elements Combining Eg. Rusting of iron 4Fe(s)+3O 2  2Fe 2 O 3 Practice: Al (s) +Cl 2(g)  ??? (a white solid is formed)

Predict the product, balance the equation A. Solid zinc (+2) combines with chlorine gas to form a solid. B. Solid magnesium combines with oxygen gas to form a white solid.

ii. Oxides combine with H 2 O A. Non-metal oxide + H 2 O  Acid Eg. CO 2(g) + H 2 O (l)  H 2 CO 3 (aq) Note: Product has H and a polyatomic ion (oxyanion) B. Metal oxide + H 2 O  Base Eg. Li 2 O (s) +H 2 O (l)  2LiOH (aq) Note: Product has a metal cation and hydroxide (oxyanion)

Predict the product balance the equation SO 2 (g) + H 2 O (l)  CaO (s) + H 2 O (l)  Remember the product is aqueous

iii. Oxides Combine Forming a Polyatomic Salt Metal oxide + non-metal oxide  salt Eg. CaO (s) + CO 2(g)  CaCO 3 Note: The salt is a polyatomic compound containing a metal cation and oxyanion

Predict the product and balance the equation Li 2 O (s) +CO 2(g)  NaO (s) +NO 2(g) 

Decomposition Reactions Reverse of synthesis Complex substance  2 or more simple ones AB  A + B Simplest Option - Compound  2 elements Δ Eg. 2HgO (s)  O 2(g) +2Hg (l) Note: This is called a thermal decomposition (Δ = heating)

Decomposition of an Acid Eg. carbonic acid  carbon dioxide +water H 2 CO 3(aq)  CO 2(g) +H 2 O (l) Note: The acid breaks down into an acid oxide and water Δ

Decomposition of a Base Eg. calcium hydroxide  calcium oxide + H 2 O Ca(OH) 2  CaO + H 2 O Note: The products are a basic oxide and H 2 O Δ

Decomposition of a Polyatomic Salt Several salts will decompose when heated Salt  basic oxide+ acid oxide Eg. calcium carbonate  calcium oxide + carbon dioxide CaCO 3  CaO + CO 2

Predicting Products for Decomposition Reactions Ionic Compound MetalNon-metal Acid Acid oxideWater

Predicting Products for Decomposition Reactions Base Basic OxideWater Polyatomic Salt Basic OxideAcidic Oxide

Predict the products and balance H 2 SO 4(aq)  AlCl 3(s)  KOH  K 2 CO 3  Δ Δ Δ Δ