Chapter 8 Chemical Equation & Reactions
8-1 Describing Chemical Reactions
Objectives: A. List evidence that suggests that a chemical reaction has occurred
Chemical reaction is a process where one or more substances change into one or more new substances w/ new physical & chemical properties
(reactants → products)Evidence: release of energy as heat-light-sound
reduction or increase in temperature or electrical energy formation of gas-precipitate- change in color or order Chemical Equation shows the chemical formulas and relative amounts of all reactants and products
B. Describe a chemical reaction using word and formula equations.
C. Interpret notations in a formula equation
Chemical equations are like recipes
(s or ↓) solid-(g or ↑) gas-(l) liquid- (aq) aqueous)-(→) produces- (↔) reaction is reversible-(∆) heat-(Mn) catalysts- (P) pressure
8-2 Balancing Chemical Equations
Objectives: A. Relate the conservation of mass to the rearrangement of atoms in a chemical reaction
Mass of reactants = mass of products, thus all equations must be balanced. Use coefficients (2 H2O) to balance equations and NEVER change subscripts.
B. Write and interpret a balanced equation for a reaction
Work from left to right- make the odd number of atoms even- polyatomic ions can be treated as a single unit- save oxygen and hydrogen atoms last
8-3 Classifying Chemical Reactions
Objectives: A. Identify type of reactions- combustion-synthesis-decomposition-single and double replacement reactions and be able to predict products. Also use activity series to see if single replacement reactions occur and memorize the solubility table to see if a double displacement reaction occurs.
Combustion: Hydrocarbon (compound containing H & C) + oxygen → CO2 + H2O CH3CH2OH + 3O2 → 2CO2 + 3H2O
When incomplete combustion occurs CO is produced instead of CO2
Synthesis: (to put together or to make) – a single compound is formed from reactants A + B → AB a. two elements form a binary compound
b. two compounds form a ternary compound
Decomposition: One reactant breaks apart into the products
AB → A + B a. binary compound breaks into its elements
Know: Metal Carbonates decompose into metal oxide & carbon dioxide
Metal Hydroxides decompose into metal oxide & water
Metal Chlorates decompose into metal chloride & oxygen
Acids decompose into nonmetal oxide & water
Displacement Reactions 1. Single Replacement: A + BC → AC + B (cations replace cations and anions replacement anions)
Use activity series pg 281 to see if one element will or will not replace another element (the higher element will replace elements below it, but an element below will not replace an element above)
2. Double Replacement AB + CD → AD + CB the two compounds switch partners w/ the cation (metal) usually written first
Use solubility table (see handout) to predict if double replacement reactions will occur (one of the predicted products must form a precipitate (be insoluble) for a reaction to occur) Partial table on pg 284
8-4 Writing Net Ionic Equations
Objectives: A. Write total ionic equations in aqueous solutions
Ionic equations separate the compounds into their individual ions showing charge of ions in an aqueous solution and it also needs to be balanced
B. Identify spectator ions and write net ionic equations in equations for aqueous solutions
Spectator ions are ions that remain unchanged from the reactant side to the product side (ions not involved in the reaction)
Net ionic equation show the equation after removing the spectator ions
Example: K2SO4(aq) + Ba(NO3)2(aq) → 2KNO3(aq) + BaSO4(s) Equation
2K+(aq) + SO4-2(aq) + Ba+2(aq) + 2NO3-(aq) → 2K+(aq) + 2NO3-(aq) + BaSO4(s) Ionic Equation
2K+(aq) and 2NO3-(aq) spectator ions
Ba+2(aq) + 2SO4-2(aq) →BaSO4(s) Net Ionic Equation