Types of Chemical Reactions

1. Types of Chemical Reactions

2. Types of Chemical Reactions • There are only five (5) different types of chemical reactions: • 1) Double Replacement • 2) Single Replacement • 3) Synthesis • 4) Decomposition • 5) Combustion

3. Reaction Type 1 – Double Replacement • Occur between two ioniccompounds • Does not happen with covalent compounds • Involves an exchange of cations • The cation of one compound trades places with the cation of another compound to form two new compounds

4. Double Replacement - Characteristics • occur in solution when the compounds are in an aqueous state (aq) • reactants are either aqueous to begin with, or solid compounds dissolved in water to form an aqueous solution of ions • in order to drive the reaction, one of the products must be removed from the aqueous solution • this can occur via one of three ways:

5. Double Replacement - Characteristics 1) Formation of a precipitate (an insoluble solid forms in the solution) • i.e.: AgNO3 (aq) + NaCl (aq) = NaNO3 (aq) + AgCl (s) • Solid silver chloride is formed as precipitate and comes out of the solution

6. Double Replacement - Characteristics 2) Formation of a gas • i.e.: FeS (aq) + 2 HCl (aq) = H2S (g) + FeCl2 (aq) • Hydrogen sulfide gas is formed and comes out of the solution

7. Double Replacement - Characteristics 3) Water is formed when a hydrogen cation unites with a hydroxide anion • i.e.: NaOH (aq) + HCl (aq) = HOH (l) + NaCl (aq) • Water (HOH) is formed and comes out of the solution

8. Identifying a Double Replacement Reaction • Double replacement reactions always have two ionic compounds on the REACTANTS side • *Two compounds react to form two new compounds* • AB + CD CB + AD • A & C are cations, B & D are anions • A & C switch places

9. Single Replacement Reactions

10. Single Replacement Reactions: Characteristics: • Atom (s) of a lone element replace the atom (s) of an element in a compound • Metals replace metals (or cations replace cations) • Non-metals replace non-metals (or anions replace anions)

11. Single Replacement Reactions: Characteristics: • Metal Cation Replacement: • For the reaction: A + BC  B + AC • A and B are cations • A “replaces” B in the compound

12. Single Replacement Reactions: Characteristics: • Non-metal Anion Replacement: • For the reaction: D + EF  ED + F • D & F are anions • D “replaces” F in the compound • Non metal replacements usually involve halogens

13. Single Replacement Example • Thermite • Thermite is a reaction that creates molten iron from rust and aluminum powder. • This reaction is typically used in certain types of welding (or for just melting stuff) Fe2O3 + 2 Al → 2 Fe + Al2O3

14. Restrictions on Single Replacement Reactions • Activity Series: • A characteristic of metals and halogens referring to their reactivity • Determines whether or not a single replacement reaction will occur or not • Metals: on the handout provided there is an activity series of metals arranged in order of decreasing activity • Non-metals (Halogens) : as you move down the group on the periodic table activity decreases

15. Restrictions on Single Replacement Reactions • A single replacement reaction WILL NOT OCCUR if the reactivity of the pure element reactant is less than that of the compound reactant • i.e.: Sn (s) + NaNO3 (aq)  • no reaction b/c tin is less reactive than sodium

16. Restrictions on Single Replacement Reactions • A single replacement reaction WILL OCCUR if the reactivity of the pure element reactant is greater than that of the compound reactant • i.e.: Zn (s) + H2SO4 (aq)  ZnSO4 (aq) + H2 (g) • Reaction occurs because the reactivity of zinc is higher than hydrogen

17. Identifying Single Replacement Reactions • Single replacement reactions ALWAYS have 1 lone element and 1 compound on the reactants side and the products side • Reactants will always be: • 1 lone element + 1 compound • Products will always be: • 1 lone element + 1 compound

18. Reaction Type #3 - Decomposition • Occurs when a single compound breaks down into two or more components • Energy is required for them to occur • Reactants will always be: • 1 compound • Products will always be: • ALWAYS more products than reactants • 2 components (either compounds or elements) • i.e.: • AB  A + B

19. Decomposition Example: • One unit breaks down into its component parts • i.e. – Remember N’Sync? They split up leaving the resulting in Justin Timberlake and four guys we don’t remember.

20. Decomposition Example 2 H2O2 (aq) → 2 H2O (l) + O2 (g) • Hydrogen peroxide naturally decomposes into water and oxygen gas • If you have old hydrogen peroxide in your house, it may have turned into a bottle of water • Don’t try and drink it though. Obviously.

21. Reaction Type #4 – Synthesis • Occurs when two or more components come together to form one compound • Energy is released when these reactions occur • Reactants will always be: • ALWAYS more reactants than products! • 2 or more components (either elements or compounds) • Products will always be: • 1 single compound • i.e.: • A + B  AB

22. Synthesis Example • Two individual components coming together to form one unit • i.e. – Beyonce & Jay-Z were both awesome on their own, but joined together to become one, even better entity.

23. Special Cases for Decomposition & Synthesis Reactions • Decomposition and Synthesis Reactions are opposite processes • Special Case #1: • A non metal oxide + water combine to form an acid • i.e.: SO3 + H2O  H2SO4 • AND an acid will decompose to form a non-metal oxide + water • i.e.: H2SO4 SO3 + H2O

24. Special Cases for Decomposition & Synthesis/Formation Reactions • Special Case #2 • A metal oxide + water combine to form a metal hydroxide • i.e.: CaO + H2O  Ca(OH)2 • A metal hydroxide will decompose into a metal oxide + water • i.e.: Ca(OH)2 CaO + H2O

25. Special Cases for Decomposition & Synthesis/Formation Reactions • Special Case #3: • All carbonates decompose into carbon dioxide and an oxide • i.e.: CaCO3 CaO + CO2 • Vice versa for synthesis/formation reactions • Special Case #4: • All chlorates decompose into oxygen and a binary salt • i.e.: KClO3 KCl + O2 • Vice versa for synthesis/formation reactions

26. Reaction Type #5 - Combustion • Also known as burning or explosions • Hydrocarbon • Compound composed of only carbon and hydrogen and sometimes oxygen • Reactants will always be: • Hydrocarbon + oxygen • Products will always be: • Carbon dioxide + water • i.e.: • C6H6 + O2CO2 + H2O