Chemical Reactions An expression of the behavior of chemical compounds 1. Expressed in a chemical equation: Reactant(s)  Product(s) (compounds reacting) To Yield(reconstituted compounds)

Parts of a Chemical Equation 2 Na (s) + 2H 2 O (l)  2NaOH (aq) + H 2(g) To Yield Subscripts: # of atoms in compound Physical State: (s), (l), (g), (aq) Coefficient: the # of cpd (moles) present. Can be factions, ONLY # that is changed Reversible reaction:  Catalyst: heat, Δ, or compound (FeO 2 )

Balancing Chemical Equations ONLY the coefficient can be changed. 1. write the compounds (criss-cross) or prefix for molecules. 2. Define the type of reaction (activity series and solubility rules) 3. Take count of the type and number of elements in the compounds. 4. Change of the coefficient ONLY to ensure that the same # and type of each are present on both sides of the arrow.

Word Problem An aqueous solution of sodium chloride and hydrogen sulfide gas is produced when aqueous sodium sulfide reacts with an excess of hydrochloric acid. Na 2 S (aq) + HCl (aq)  NaCl (aq) + H 2 S (g)

Word Problem Sampler Solid lead is dissolved in aqueous sulfuric acid to precipitate lead (III) sulfate and hydrogen gas is evolved. Pb (s) + H 2 SO 4(aq)  Pb 2 (SO 4 ) 3(s) + H 2(g)

Type of Reactions 1. Synthesis Reaction 2. Decomposition Reaction 3. Single Replacement 4. Double Replacement 5. Combustion Reaction.

Synthesis Reaction The reaction of two or more reaction to produce a single produce. a. Form: A 2 + 2CB  2ACB Sulfur dioxide and water react to produce sulfurous acid SO 2 + H 2 O  H 2 SO 3

Decomposition Reaction A reaction where one or more reactants breakdown into several simpler forms. a. Form: AB 2  A + 2B b. Requires energy to breakdown! Ammonia breaks down to nitrogen gas and hydrogen gas 2NH 3  N 2 + 3H 2

Single Replacement A reaction where the metals (or non- metal) trade places. a. Form: AB + C  CB + A b. Depends directly of the activity of the metal.

Activity Series Back of periodic table: **The more active the metal (or non- metal), the more likely it is to replace the less active metal (or non-metal). **All metals will replace Gold according to the list. **Lithium will replace all metals. **Fluorine is the most active non-metal.

Sample: Single Replacement Sodium plus copper (II) chloride yields sodium chloride and copper metal. 2Na + CuCl 2  Magnesium metal reacts with potassium hydroxide to yield Mg + KOH 

Double Replacement a reaction where the metals or non- metals trade positions. (like replaces like). Form: AB + CD  AD + CB A precipitate can be formed as one of the produces often.

Sample: Double Replacement Silver (I) nitrate plus sodium chloride to yield sodium nitrate and silver (I) chloride. **Balance the charge then balance the equation** AgNO 3 + NaCl  AgNO 3 + NaCl  NaNO 3 + AgCl

Solubility Ionic compounds ability to dissolve in water. Solubility Rule: Note the Periodic Reference Page Ba(NO 3 ) 2 Pb 2 (SO 4 ) 3 C2H4C2H4 AgCl 2 CaCO 3

Combustion Reaction The burning of hydrocarbons in the presents of oxygen and energy. –Form: Hydrocarbon gas + oxygen  carbon dioxide and water. (a complete burn). CH 4 + O 2  CO 2 + H 2 O (a complete burn) Or CH 4 + O 2  CO + H 2 O (a dirty burn)

Net Ionic Equations Spectator Ions: Occurs when reactant compounds dissolve into solution and ions remain in solution. –Pay attention to the physical state. (s) indicates that it has NOT ionized (broken down) –Pay attention to the solubility rules on the periodic table. –The ions that are on both sides of the equation are called spectator ions and cancel. –The ions that remain form a net ionic equation.

Sample: Net Ionic Equation Pb(ClO 4 ) 2 (aq) + NaI (aq)  PbI 2(s) + NaClO 4(aq)

Chemical Equation 2Na (s) + 2H 2 O (l)  2NaOH (aq) + H 2(g) reactants To Yield Products (s) : solids (l) : liquid (aq): aqueous (g): gas Coefficient: Big number in front. # of compounds present (# of moles). ONLY number that can change. Subscript: # of atoms present in the compound Reversible; Catalyst

Chemical Reaction An expression of the behavior of chemical compounds Expressed in a chemical equation: To yield Reactant(s)  Product(s) (stuff reacting)(reforming of stuff) ****Energy is required to break or form****

Balancing Chemical Equations Same number and type of each element on both sides of the . *Same by changing the coefficient ONLY. *Coefficient in front of cpd ONLY. *Once the charges of a cpd are balanced, NEVER change a subscript! Review: Writing formula units and molecular formula Criss-cross to balance charge