Types of Reactions

Generals about writing Equations Reactants on the left and products on the right Symbols Ex: g for gas, l for liquid, s for solid aq for aqueous (dissolved in water) Catalyst goes above the arrow KI Ex H2O2(aq) ---> H2O(l) + O2(g) Diatomic Molecules - BrINClHOF Elemental state - Br2I2N2Cl2H2O2F2

Chapter 8: Chemical Reactions -- Types of Chemical Reactions -- Classifying reactions Knowing what kind of reaction is occurring can help you to predict the products of the reaction Five types of reactions Synthesis/Combination Decomposition Single-replacement Double-replacement Combustion Five major types of reactions Easier to write the equation if you know the type of reaction

1. Synthesis (Combination) Two or more substances react to form a single substance A + B --> AB Ex) SO3(g) + H2O(l) --> H2SO4(aq) Usually gives off energy when forming bonds Examples 2K(s) + Cl2(g)  2KCl(s) S(s) + O2(g) SO2(g) 2S(s) + 3O2(g)  2SO3(g) Fe(s) + S(s)  FeS(s)

2Na + Cl2  2NaCl

2. Decomposition A single compound is broken down into simpler products AB --> A + B Requires energy to break chemical bonds (heat, light, electricity) Examples

2NI3  N2 + 3I2

Elephant toothpaste http://www.youtube.com/watch?v=ezsur0L0L1c

3. Single Replacement Reactions One element replaces a second element in a compound A + BC --> AC + B Ex) Zn(s) + H2SO4(aq) --> ZnSO4(aq) + H2(g) A metal may replace a metal or a nonmetal may replace a nonmetal Activity Series - list of metals in order of decreasing activity Nonmetals reactivity decreases as you go down the periodic table

Activity Series of Metals (Decreasing reactivity) Activity series of metals A table listing metals in order of decreasing reactivity Metals will displace other metals Activity Series of Metals (Decreasing reactivity) -----------------------------------------------------------------------------------------------------> Li K Ca Na Mg Al Zn Fe Pb H Cu Hg Ag Examples Mg + 2HCl  MgCl2 + H2 Cu + HCl  no reaction 2Fe + 6HCl  2FeCl3 + 3H2

3. Single replacement reactions Ex) Which element will get kicked out? Hint- figure out which is more reactive- the more reactive one will bond and the less reactive one will be kicked out. Al(s) + H2SO4(aq) 

3. Single replacement reactions Ex) Which element will be replaced? (or kicked out?) Cl2(g) + 2 KI(aq) --> Cu + FeSO4 

Fe2O3 + 2Al → 2Fe + Al2O3 Brainiac on Thermite http://www.youtube.com/watch?v=GyVD8V0016w

4. Double Replacement Exchange of positive ions between two ionic compounds. Just swap the positive ions (the cations) and write the new formula. A+B- + C+D- --> C+B- + A+D- Examples Barium chloride and potassium carbonate solutions react. BaCl2(aq) + K2CO3(aq)  BaCl2(aq) + K2CO3(aq)  BaCO3(s) + 2KCl(aq) BaCO3 is the precipitate. Sodium hydroxide and lead (II) nitrate solutions react. NaOH(aq) + Pb(NO3)2(aq)  2NaOH(aq) + Pb(NO3)2(aq)  2NaNO3(aq) + Pb(OH)2(s) Pb(OH)2 is the precipitate. Product usually a gas, precipitate, or molecular compound like water

Lead nitrate reacts with Potassium iodide http://www.youtube.com/watch?v=DITY2rXYU-I

5. Combustion Reactions Oxygen reacts with another substance, often producing heat and light Oxygen (O2) will always be one of your reactants Often involve hydrocarbons Compounds of hydrogen and carbon Combustion of hydrocarbons produces a lot of energy, therefore, hydrocarbons are used as fuels. Examples: methane, propane, butane, octane

5. Combustion Reactions Two types of combustion 1. Complete combustion Always produces water and CO2 CxHy + O2(g) --> CO2(g) + H2O(g) + energy 2. Incomplete combustion Two more products: CO and C CxHy + O2(g) --> CO2(g) + H2O(g) + CO(g) + C(s) + energy

Methane mamba Let’s try it!