CHEMICAL REACTIONS

chemical reaction a reaction during which substances change into one or more new substances with different physical and chemical properties reactants  products

Law of Conservation of Matter in any chemical reaction, the mass of the products is always equal to the mass of the reactants, matter can't be created or destroyed

Types of Chemical Reactions 1. Synthesis Reactions the combination of two or more simple substances to form a more complex substance also known as combination or addition reaction A + B  AB ex. H2 (l) + O2 (l)  H2O (g)

Challenger disaster, 1986…

special case of synthesis: Combustion Reaction if oxygen rapidly reacts with another element it can form a more complex compound by burning C(s) + O2 (g)  CO2 (g) S (s) + O2 (g)  SO2 (g)

2. Decomposition Reactions the breakdown of large, more complex molecules or ionic compounds into smaller and simpler entities AB  A + B ex. H2O2 (l)  O2 (g) + H2O (l) (hydrogen peroxide) Coefficient up front tells you that there are two H2O2

Writing Chemical Equations word equation identifies reactant and product by name, ex. sodium + chlorine  sodium chloride skeleton equation lists reactants and products with + and signs, shows state ex. Na (s) + Cl2 (g) --> NaCl (s) balanced chemical equation reflects the law of conservation of mass ex. 2 Na(s) + Cl2 (g) --> 2 NaCl

Steps in Balancing Chemical Equations 1. is the skeleton equation accurate? 2. balance atoms on both sides, other than H and O 3. polyatomic ions are balanced as a whole IF whole on both sides 4. balance H, O 5. balance lone elements, ex. Cl2 6. check!

ex1. sulfur dioxide gas reacts with oxygen gas to produce gaseous sulfur trioxide

ex2. when dissolved in water, copper (II) nitrate reacts with potassium hydroxide to form a water-soluble potassium nitrate and solid copper (II) hydroxide precipitate

In Groups Balance 1. KOH + SO2 --> K2SO3 + H2O 2. Al4C3 + H2O --> Al(OH)3 + CH4 3. Na2CO3 + H3PO4 --> Na3PO4 + H2O + CO2 4. CaC2 + H2O --> Ca(OH)2 + C2H2 5. Al + NaOH --> Na2AlO3 + H2 6. KNO3 --> KNO2 + O2

3. Single Displacement Reactions reaction of an element and a compound to produce a new compound ex. AB + C  AC + B

ex. solid zinc in lead (II) nitrate solution will give you solid lead and aqueous zinc nitrate

4. Double Displacement Reactions a chemical reaction in which two compounds in aqueous solution react to form two new copounds AB + CD  AD + CB

ex. aqueous silver nitrate + aqueous calcium chloride  silver chromate + calcium nitrate

precipitate a solid that forms as a result of a chemical reaction between two aqueous solutions use the solubility chart to identify which one!