Chapter 20 Predicting the Products of a Chemical Reaction Chapter 11 TYPES OF CHEMICAL REACTIONS Chapter 20 Predicting the Products of a Chemical Reaction

I can ……. double replacement Precipitation Acid / base classify reactions: double replacement Precipitation Acid / base predict and write the products of the above types of reactions. predict the states of the reactants by using the solubility rules. identity spectator ions and explain what they do.

Double Replacement Reactions Reactants are always 2 compounds Products are always 2 new compounds The same charge ions switch partners

We do not just “switch” the cations (metals) to create the products. NaCl + BaO → NaO + BaCl is not correct !! You must make sure you follow the rules of formula writing when writing new compounds: Predict what is formed in the reaction Check the charges of each ion Criss-cross and drop charges to write correct chemical formulas Balance the final equation using coefficients

Examples:. 1. Predict what is formed in the reaction. 2 Examples: 1. Predict what is formed in the reaction 2. Check the charges of each ion 3. Criss-cross and drop 4. Write correct formula 5. Balance the final equation MgCl2 + CaS  MgS + CaCl2 Be(NO3)2 + K2SO4  2KNO3 + BeSO4

Beautiful Chemical Reactions Specific Types of Double Replacement Reactions Precipitation – two aqueous solutions react to form one solid precipitate and an aqueous solution Example: KCl(aq) + AgNO3(aq)  KNO3 (aq) + AgCl (s) Beautiful Chemical Reactions

Specific Types of Double Replacement Reactions Acid/Base “Neutralization – An acid (always starts with “H”) and a base (always ends in “OH”) react to form a salt and water Example: HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)

Acid – Base Neutralization Reactions (write these reactions) Acid + Base  Salt + Water HCl + NaOH  NaCl + H2O HNO3 + KOH  KNO3 + H2O Copy

Double Replacement – Precipitation Reactions Soluble – able to be dissolved in water (aq) Insoluble – not able to be dissolved in water (s) Na+ and Cl- are called SPECTATOR IONS. They do not react and remain dissolved in solution Solid precipitate

Double Replacement – Precipitation Reactions Ionic compounds that dissolve in water split apart into ions. Ions conduct electricity when dissolved in solution. Electrolytes are any ionic compounds which are soluble and thus conduct electricity Ionic compounds that do not dissolve are insoluble and are called precipitates. These compounds form a solid when in solution

Double Replacement – Precipitation Reactions Solubility was discovered by trial and error. Over time, scientists developed a set of rules (solubility rules) which help predict the solubility of a substance When new compounds are formed in a double replacement reaction, you must identify the solubility (state) of the products Soluble = (aq) Insoluble = (s) - precipitate

Double Replacement – Solubility Rules SOLUBILITY RULES FOR COMMON IONIC COMPOUNDS IN WATER Mainly water soluble NO­3- All nitrates are soluble C2H3O2- All acetates are soluble ClO3- All chlorates are soluble Cl- All chlorides are soluble EXCEPT AgCl, Hg2Cl2, and PbCl­2 Br- All bromides are soluble EXCEPT AgBr, Hg2Br2, and HgBr­2 I- All iodides are soluble EXCEPT AgI, Hg2I2, and HgI­2 SO42- All sulfates are soluble EXCEPT CaSO4, SrSO4, BaSO4, PbSO4, Hg2SO4, and Ag2SO4 Mainly water insoluble S2- All sulfides are insoluble EXCEPT those of groups 1 & 2 and (NH4)2S CO32- All carbonates are insoluble EXCEPT those of group 1 and (NH4)2CO3 CrO42- All chromates are insoluble EXCEPT those of group 1 and (NH4)2CrO4 PO43- All phosphates are insoluble EXCEPT those of group 1 and (NH4)3PO4 OH- All hydroxides are insoluble EXCEPT those of group 1, Ba(OH)2, Sr(OH)2, and Ca(OH)2 Double Replacement – Solubility Rules

Double Replacement Reactions

Draw a picture of each solution showing the ions present Consider 2 Beakers: One with aqueous silver nitrate, one with aqueous barium chloride Draw a picture of each solution showing the ions present Ba 2+ Ag1+ Cl 1- NO31- Cl 1-

Consider 2 Beakers: One with aqueous silver nitrate, one with aqueous barium chloride Draw a picture after the solutions are mixed (before new compounds are formed Ag1+ NO31- Ba 2+ Cl 1- Cl 1-

Consider 2 Beakers: One with aqueous silver nitrate, one with aqueous barium chloride Predict the products for any reaction that occurs and draw what would be in the beaker (check solubility rules) Write an equation for the reaction: 2AgNO3 (aq) + BaCl2 (aq)  2AgNO3 (aq) + BaCl2 (aq)  2AgCl (s) + Ba(NO3) 2 (aq)

Consider 2 Beakers: One with aqueous silver nitrate, one with aqueous barium chloride Spectator Ions – Ions that remain as ions on both sides of the equation (do not become part of a precipitate) List the spectator ions in this example: NO31- Ba 2+

Double Replacement – Precipitation Reactions Use the solubility rules to predict what will happen when the following solutions are mixed. Label each new compound with an (aq) (electrolyte) or (s) (precipitate). Circle the ions that would be spectator ions 2KNO3 + BaCl2   Na2SO4 + Pb(NO3)2 Na2S + Cu(NO3)2 2NH4Cl + Pb(NO3)2 swap front ions Criss-cross charges balance equations  Ba(NO3)2 (aq) + 2KCl (aq)  2 NaNO3 (aq) + PbSO4 (s)  2 NaNO3 (aq) + CuS (s)  2 NH4NO3 (aq) + PbCl2 (s)

Chapter 20.1 I can ……. Identify oxidation – reduction reactions which are also called Redox reactions Predict products for redox reactions

Oxidation Reduction Reactions (Synthesis, Decomposition, Single Replacement, Combustion) In these reactions, electrons are transferred from one atom to another Atoms that lose electrons (become more positive) are oxidized Atoms that gain electrons (become more negative) are reduced LEO says GER or OIL RIG Lose Electron Oxidized Oxidation Is Loss Gain Electrons Reduced Reduction Is Gain  

How to determine if element gains or loses electrons from its charge e- carry negative charge! Remember this! Element loses e- Element “-” - so element becomes more positive 0 - -1 = 0 +1 Element gains e- Element “+” - so element becomes more negative 0 + -1 = 0 - 1

Oxidation Reduction Reactions Example 1: Identify the element that has been oxidized and the element that has been reduced. 2Ca + O2  2CaO Step 1: Write the charge above any ions that are part of a compound Step 2: Write a zero above any elements that exist by themselves (or as a diatomic) Step 3: Label atoms that have gained electrons (become more negative) as reduced, and label atoms that have lost electrons (become more positive) as oxidized 2+ 2- Ca became more positive So Ca lost electrons so it was oxidized Oxygen became more negative So O gained electron so it was reduced

Oxidation Reduction Reactions Example 2: Identify the element that has been oxidized and the element that has been reduced. Zn + 2HCl  ZnCl2 + H2 1+ 1- 2+ 1- Zn became more positive So Zn lost electrons so Zn was oxidized H became more negative So H gained electrons so H was reduced

Predicting Products of ReDox Reactions Synthesis – More than one reactant, but a single product Example: 2Mg + O2  2MgO Decomposition – A single reactant, multiple products 2KNO3  2 KNO2 + O2

Predicting Products of ReDox Reactions Combustion – Reactants are always a hydrocarbon and oxygen, products are always CO2 (carbon dioxide) and H2O (water) Examples of hydrocarbons (must have C and H): CH4 C2H6 CH2O C6H12O6 Example: CH4 + 2O2  CO2 + 2H2O

One element replaces another element in a compound SINGLE REPLACEMENT: One element replaces another element in a compound element + compound = new element + new compound A + BC  B + AC

Predicting Products of ReDox Reactions Single Replacement – an element switches partners: reaction does not always happen; depends on the Activity Series (or reactivity series) Example of a single replacement that does occur: Na + MgCl2  NaCl + Mg

Na is higher up on chart than Mg so Na is more reactive If a metal is higher on the chart, it will replace a metal that is lower on the chart Na is higher up on chart than Mg so Na is more reactive

NR – Ca is lower on chart than Na Example 1: Ca + ZnI2  Example 1: Ca + ZnI2  CaI2 + Zn Example 2: Ca + NaI  NR – Ca is lower on chart than Na Write NR for No reaction when a reaction does not occur

a. calcium, tin d. iron, copper For each of the following pairs of elements, circle the one that will replace the other element in a compound a. calcium, tin d. iron, copper b. bromine, fluorine e. iodine, chlorine c. aluminum, potassium f. silver, lead

More Practice: Skeleton Equations – formulas only Cu + AgNO3  CuNO3 Ca + HCl  CaCl2 + H2 Mg + CuCl2  MgCl2 + Cu Fe + CuSO4  FeSO4 + Cu Zn + HCl  ZnCl2 + H Cl2 + NaBr  NaCl + Br

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new compound + new compound DOUBLE REPLACEMENT: AB + CD  CB + AD compound + compound = new compound + new compound Cations and Anions switch places But there must be a reason why they switch places ……………

C+ B­ D­ A+ A gas forms and leaves A precipitate forms and settles out Water is formed

K+ Solubility Rules: 1. Na+ NH4 salts are soluble 2. NO3 ­1- salts are soluble 3. Cl­1- salts are soluble EXCEPT: AgCl PbCl2 and HgCl 4. SO4 2-­ salts are soluble EXCEPT: BaSO4 PbSO4 and CaSO4

Four general types of chemical reactions + .. + +

Four general types of chemical reactions + .. + +

Synthesis

Decomposition

Synthesis Decomposition Single Replacement

Synthesis Decomposition Single Replacement Double Replacement

•• Produces oxides of the fuel •• Hydrocarbon or any C,H,O compound COMBUSTION: (Burning) •• Reacts with oxygen •• Produces oxides of the fuel •• Hydrocarbon or any C,H,O compound •• Produces CO2 and H2O •• Produces energy (heat and light) •• Exothermic reaction •• Example: CH4 + 2O2  CO2 + 2 H2O

C + O2  CO2 2Ca + O2  2CaO Na + O2  Na2O OXIDATION: •• Metal or nonmetal reacts with oxygen •• Produces an oxide of the element •• Exothermic reaction­ produces heat Examples: C + O2  CO2 2Ca + O2  2CaO Na + O2  Na2O

•• Synthesis A + B  AB Decomposition AB  A + B Single Replacement A + BC  B + AC •• Double Replacement AB + CD  AD + CB Acid – Base (Neutralization) Acid + Base  Salt + Water Combustion Oxidation

Predicting Products of ReDox Reactions Synthesis – More than one reactant, but a single product Example: 2Mg + O2  2MgO Decomposition – A single reactant, multiple products 2KNO3  2 KNO2 + O2 +2 -2 +1 +3 -2 +1 +5 -2