Reaction Prediction
You should already know... how to balance chemical equations. the five common types of chemical reactions. how to use the activity series. the solubility rules and how to apply them. the molarity equation and how to use it. the dilution equation and how to use it.
Reaction Prediction On the AP Exam, Free-Response Question 4 is always reaction prediction You are given three sets of reactants and asked to write the balanced net ionic equations. You also have a follow-up question to answer for each reaction.
Reactions in Solution In many chemical reactions in solution, only some of the dissolved components actually participate in the reaction and change as a result.
Reactions in Solution Chemical reactions as we have written them so far are called molecular equations. In a complete ionic equation, all substances that are strong electrolytes are written as ions.
Electrolyte a material that dissolves in water to give a solution that conducts electricity material must produce sufficient ions to allow conduction
Strong Electrolytes solute present in solution as ions (completely dissociate) soluble salts, strong acids and strong bases NaCl in water NaCl Na + + Cl -
Nonelectrolyte solute present in solution as molecules (disperse, but do not dissociate) insoluble salts, molecular compounds anything not in solution Methanol (a molecular compound) in water
Weak Electrolyte solute partially ionizes in solution weak acids and weak bases
Strong electrolytes: soluble salts, strong acids and strong bases Weak electrolytes: weak acids and weak bases Nonelectrolytes: insoluble salts, molecular compounds, anything not in solution (labeled as solid, liquid, gas)
Reactions in Solution In a complete ionic equation, all substances that are strong electrolytes are written as ions. Strong electrolytes: soluble salts, strong acids and strong bases that are IN SOLUTION
Reactions in Solution Molecular equation: K 2 CrO 4 (aq) + Ba(NO 3 ) 2 (aq) BaCrO 4 (s) + 2KNO 3 (aq) Complete ionic equation:
Reactions in Solution Complete ionic equations reveal that some of the ions in solution do not participate in the reaction. In other words, they are identical as a reactant and as a product. These are called spectator ions.
K 2 CrO 4 (aq) + Ba(NO 3 ) 2 (aq) BaCrO 4 (s) + 2KNO 3 (aq)
Reactions in Solution When spectator ions are removed and the equation is rewritten, only those ions that actually participated in the reaction are now shown. This is called a net ionic equation.
Reactions in Solution 2K + + CrO Ba NO 3 - BaCrO 4 + 2K + + 2NO 3 - Net ionic equation:
Reaction Prediction Solutions of potassium bromide and lead (II) nitrate are mixed.
Aqueous calcium acetate and lithium carbonate are mixed. Reaction Prediction
An ammonium chloride solution is added to a solution of zinc sulfate. Reaction Prediction Use a particulate drawing to show why there is no reaction occurring.
Solutions of acetic acid and sodium cyanide are mixed. Reaction Prediction
Solid sodium hydroxide is added to a solution of hypochlorous acid. Reaction Prediction
Magnesium turnings are added to a solution of lead (II) acetate.
Reaction Prediction Fluorine gas is bubbled into a potassium bromide solution.
Reaction Prediction Propane (C 3 H 8 ) is burned in air.
Memorize.... Sulfuric acid is unique. H 2 SO 4 is the only polyprotic strong acid. All strong acids completely ionize. H 2 SO 4 ionizes to H + and HSO 4 - ! ( NOT H + and SO 4 2- !)
Sulfuric acid is added to a magnesium hydroxide solution.
Memorize.... The following substances always decompose in this way: H 2 SO 3 H 2 O + SO 2 H 2 CO 3 H 2 O + CO 2 NH 4 OH NH 3 + H 2 O
Excess nitrous acid is poured into a solution of potassium sulfite.
Memorize.... Synthesis Reactions: a metal + a nonmetal a binary salt metallic oxides + water bases nonmetallic oxides + water acids
Memorize.... Decomposition Reactions: metallic carbonates metallic oxides + CO 2 metallic chlorates metallic chlorides + O 2 metallic hydroxides metallic oxides + H 2 O
Reaction Prediction Potassium carbonate is strongly heated.