Types of Reactions

Updated types of reactions… Regular Chemistry AP Chemistry Synthesis Decomposition Single Replacement Double Replacement Combustion Precipitation Reactions Acid-Base Reactions: involves electrolytes & neutralization Redox Reactions = most reactions are redox! Double replacement = metathesis reactions (many precipitation & acid-base reactions)

REACTIONS Anatomy of an AP Chemistry Test

AP Chemistry Exam Part 1] 75 Multiple Choice 90 minutes No calculator Periodic Table available 50% of total exam score Part II] Free Response Answer 6 required questions Periodic table, formulas, constants & reduction potential table available 50% of total exam score

Part 2] Free Response 1-Equilibrium Question: 20% of free response score, calculator OK 2-Calculation Question: 20% of free response score, calculator OK 3-Calculation Question: 20% of free response score, calculator OK, may be laboratory-based question 4-Predicting Reaction: 10% of free response score, no calculator, answer 3 of 3 statements, provide balanced equation, answer a question about reaction 5-Non-calculation question: 15% of free response score, no calculator, lab based if #3 is not 6-Non-calculation question: 15% of free response score, no calculator

AP CHEMISTRY EXAM; PART 2B FREE RESPONSE How to earn points on writing reactions:

Calcium metal is added to water Job #1: classify, recognize common reactions Job #2 Predict products Metals + water produce insoluble hydroxides and hydrogen gas Ca + H 2 0  1 of 3 points possible Ca + H 2 0  Ca(OH) 2 + H 2 3 of 3 points possible Ca + H 2 0  Ca +2 +OH - + H 2 2 of 3 points possible Ca +2  Ca +2 + OH - + H 2 1 of 3 points possible Ca (aq)  Ca +2 + OH - + H + 0 of 3 points possible

Precipitation Reactions When one mixes ions that form compounds that are insoluble (as could be predicted by the solubility guidelines), a precipitate is formed.

Metathesis (Exchange) Reactions Metathesis comes from a Greek word that means “to transpose” AgNO 3 (aq) + KCl (aq)  AgCl (s) + KNO 3 (aq)

Metathesis (Exchange) Reactions Metathesis comes from a Greek word that means “to transpose” It appears the ions in the reactant compounds exchange, or transpose, ions AgNO 3 (aq) + KCl (aq)  AgCl (s) + KNO 3 (aq)

Metathesis (Exchange) Reactions Metathesis comes from a Greek word that means “to transpose” It appears the ions in the reactant compounds exchange, or transpose, ions AgNO 3 (aq) + KCl (aq)  AgCl (s) + KNO 3 (aq)

Net Ionic Equation To form the net ionic equation, cross out anything that does not change from the left side of the equation to the right. The only things left in the equation are those things that change (i.e., react) during the course of the reaction. Ag + (aq) + Cl - (aq)  AgCl (s)

Displacement Reactions In displacement reactions, ions oxidize an element. The ions, then, are reduced.

Oxidation-Reduction Reactions An oxidation occurs when an atom or ion loses electrons. A reduction occurs when an atom or ion gains electrons.

Oxidation-Reduction Reactions One cannot occur without the other.

Displacement Reactions In this reaction, silver ions oxidize copper metal. Cu (s) + 2 Ag + (aq)  Cu 2+ (aq) + 2 Ag (s) Copper is put into a solution of silver nitrate:

How many points? Cu + AgNO 3  Ag + Cu(NO 3 ) 2 1 point for one correct product= Ag Cu +2 + Ag + + NO 3 -  Ag + + Cu +2 + NO point for one correct product= Cu +2 Cu + Ag +  Ag + Cu(NO 3 ) 2 2 points; one for correct reactants & one for correct product

Activity Series Use activity series to predict metal displacement; halogen displacement

Gas-Forming Reactions These metathesis reactions do not give the product expected. The expected product decomposes to give a gaseous product (CO 2 or SO 2 ). CaCO 3 (s) + HCl (aq)  CaCl 2 (aq) + CO 2 (g) + H 2 O (l) NaHCO 3 (aq) + HBr (aq)  NaBr (aq) + CO 2 (g) + H 2 O (l) SrSO 3 (s) + 2 HI (aq)  SrI 2 (aq) + SO 2 (g) + H 2 O (l)

Gas-Forming Reactions This reaction gives the predicted product, but you had better carry it out in the hood, or you will be very unpopular! Just as in the previous examples, a gas is formed as a product of this reaction: Na 2 S (aq) + H 2 SO 4 (aq)  Na 2 SO 4 (aq) + H 2 S (g)

Homework Classify reactions the old way ◦ Synthesis (redox), decomposition (redox), single replacement (redox), double replacement (metathesis) Use activity series to predict products in displacement reactions (8-1)