Synthesis Reactions
Description: Elements are joined together.
General Form: A+X→AX$$A + X \rightarrow AX$$
Example: $$2H2 + O2 \rightarrow 2H_2O$$
Two substances combine to form one new compound.
Reaction of pure elements with oxygen and sulfur (e.g., $$Fe + O2 \rightarrow Fe2O_3$$).
Reactions of metals with Halogens.
Decomposition Reactions
Description: A compound breaks into parts.
General Form: AX→A+X$$AX \rightarrow A + X$$
Example: $$2H2O \rightarrow 2H2 + O_2$$
Examples to memorize:
Metal carbonates (e.g., $$CaCO3(s) + heat \rightarrow CaO(s) + CO2(g),$$, $$2NaHCO3 (s) + heat \rightarrow Na2CO3(s) + H2O(l) + CO_2 (g)$$).
Metal chlorates ($$2KClO3(s) +heat \rightarrow 2KCl(s) + 3O2(g)$$).
Unstable Oxyacids ($$H2CO3(aq) \rightarrow CO2(g) + H2O(l ),$$, $$H2SO3(aq) \rightarrow SO2 (g) + H2O (l)$$).
Ammonium hydroxide (ammonia water): $$NH4OH \rightarrow NH3 (g) + H_2O (l)$$.
Single Replacement Reactions
Description: A single element replaces an element in a compound.
General Form: A+BX→AX+B$$A + BX \rightarrow AX + B$$ or BX+Y→BY+X$$BX + Y \rightarrow BY + X$$
Example: $$Zn + 2HCl \rightarrow H2 + ZnCl2$$
Replacement of:
Metal Cation replacement (Metals by another metal, Hydrogen in water by a metal, Hydrogen in an acid by a metal).
Halogens anion replacement by more active halogens.
Double Replacement Reactions
Description: An element from each of two compounds switch places.
General Form: AX(aq)+BY(aq)→AY+BX$$AX(aq) + BY(aq) \rightarrow AY + BX$$
Example: $$H2SO4 + 2NaOH \rightarrow Na2SO4 + 2H_2O$$
The ions of two compounds exchange places in an aqueous solution to form two new compounds.
One of the products must be a precipitate, a gas, or water.
Types of Reactions
Synthesis Reactions
Decomposition Reactions
Single Replacement Reactions
Double Replacement Reactions