Types Of Chemical Reactions

Objective Distinguish between the 5 different types of reactions Predict the products of a reaction Predict the physical states of products

5 Types of Reactions Composition/Synthesis Decomposition Single Replacement Double Replacement Combustion

Composition Reactions aka synthesis rxn When two or more substances react to form a single product 2 reactants → 1 product A + X → AX H2 + O2 → MgO + CO2 → 2 H2O MgCO3

Decomposition Occurs when a compound is broken down into simpler substances Single reactant yields two or more products (1 reactant → 2 products) forms a common gas as one of the products; CO2, O2, SO2, H2O

Decomposition Examples AX → A+ X HgO → CaCO3 → Hg + O2 CaO + CO2

Single Replacement One substance replaces another A metal replaces a metal, if it is more active A non-metal replaces a non-metal, if it is more active

Single Replacement Examples A and B are metals; X and Y are non-metals A + BX → AX + B OR Y + BX → BY + X Mg + Zn(NO3)2 → Cl2 + KBr → Mg (NO3)2 + Zn KCl + Br2

Double Replacement An exchange of partners The metal replaces the metal and the non-metal replaces the non-metal AX + BY → AY + BX Na2S + Cd(NO3)2 → BaCl2 + K2CO3 → NaNO3 + CdS BaCO3 + KCl

Composition A + X → Fe + O2 → H2O + SO3 → AX FeO H2 SO4 Two elements or compounds combine to form a single substance A + X → Fe + O2 → H2O + SO3 → AX FeO H2 SO4

5 Kinds of Decomposition Reactions Metallic Carbonates Metallic Hydroxides Metallic Chlorates Oxy Acids Oxides

Metallic Carbonates CaCO3 → Metal oxide and carbon dioxide formed CaO + CO2

Metallic Hydroxides Many metallic hydroxides (OH-), when heated, decompose into metallic oxides and water. Ca(OH)2 → Metal oxide and water formed Exceptions to the rule: NaOH and KOH CaO + H20

Metallic Chlorates (ClO3-), when heated, decompose into metallic chlorides and oxygen 2KClO3 → metal chloride and oxygen formed 2KCl + 3O2

Oxy Acids Some oxy acids, when heated, decompose into nonmetallic oxides and water Seltzer Water H2CO3 → Acid Rain H2SO3 → CO2 + H2O SO2 + H2O

Oxides Some oxides, when heated, decompose. 2HgO → 2Pb O2 → 2Hg + O2 2PbO + O2

4 Kinds of Single Replacement Reactions Metal w/ more active metal Hydrogen in acids w/ more active metal Hydrogen in water w/ by most active metals Halogen w/ more active halogen

Metal w/ more active Metal Replacement of a metal in a compound by a more active metal (PCS Mazintl) Zn + CuSO4 → Zinc replaces the copper, therefore zinc is more active ZnSO4 + Cu (s)

Hydrogen in acids w/ more active metals Replacement of hydrogen, in acids, by metals more active than hydrogen (PCS Mazintl) Zn + H2SO4 → The corresponding metallic compound and hydrogen gas are formed Zn SO4 + H2 (g)

Hydrogen in water w/ most active metals Replacement of hydrogen, in water, by the most active metals. Which Metals? All Group I and some of Group II Ca + 2 H2O → A hydroxide and hydrogen gas are formed Ca(OH)2 + H2 (g)

Halogen w/ more active halogen Replacement of a halogen by a more active halogen Cl2 + 2 KBr → Br2 + 2 KI → MgBr2 + I2 → The corresponding metallic compound and elemental halogen are formed 2 KCl + Br2 2 KBr + I2 no reaction because Br is more active than I, so I will not replace Br

Activity Series of the elements A + BX → AX + B If A replaces B, then A is more active than B If an element is above another element on the chart, then it is more active, and will replace the lower positioned element All metals above hydrogen displace hydrogen from hydrochloric acid or dilute sulfuric acid.

More Active P.C.S. Mazintl Activity of Halogens P potassium Fluorine C calcium Chlorine S sodium Bromine M magnesium Iodine a aluminum z zinc i iron n nickel t tin l lead HYDROGEN Copper Mercury Silver More Active

Example Zn (s) + CuSO4 (aq)→

More Active P.C.S. Mazintl Activity of Halogens P potassium Fluorine C calcium Chlorine S sodium Bromine M magnesium Iodine a aluminum z zinc i iron n nickel t tin l lead HYDROGEN Copper Mercury Silver More Active

Example Zn (s) + CuSO4 (aq)→ ZnSO4 (aq) + Cu (s) Mg (s) + Zn(NO3)2 (aq) → ZnSO4 (aq) + Cu (s) Mg (NO3)2 (aq) + Zn (s)

Double Replacement AX + BY → AY + BX usually takes place in a solution of water…all reactant solutions are aqueous 2 compounds → 2 different compounds 1 of these will not be soluble in water…solid (s) The soluble (dissolved) compound is aqueous…(aq) In order for you to know if the reaction has occurred, a solid or gas must form 1 product will typically be: solid: precipitate gas: CO2 SO2 NH3

Solubility Rules for Double Dis(RE)placement Reactions How to determine which product is the precipitate Na+ K+ NH4+ NO3- [ Will always be soluble in water. Tells you what won’t precipitate, so assume the other one will

Examples CaCO3 + 2 HCl → Pb(NO3)2 + KI → NaOH + KI → → CaCl2 + H2CO3 H2O + CO2 PbI2 + 2 KNO3 no reaction because both products are soluble NaI + KOH

Combustion An element or compound reacts with oxygen Usually produces heat → Exothermic Combustion of a hydrocarbon always produces carbon dioxide and water 2 Mg + O2 → 2 CH3OH + 3 O2 → 2 MgO + heat 2 CO2 + 4 H20 + heat

Writing Molecular, Complete Ionic, and Net Ionic Equations Molecular Equations: an equation showing the complete neutral formulas for every compound in the reaction. AgNO3 (aq) + NaCl (aq)→ AgCl(s) + NaNO3 (aq)

Complete Ionic Equation of : Complete Ionic Equations: equations that show reactants and products as they are actually present in solution. Ionic compounds dissociate (dissolve) in water, so they are written as individual ions…if the compound is soluble…check your solubility rules Complete Ionic Equation of : AgNO3 (aq) + NaCl (aq)→ AgCl(s) + NaNO3 (aq)

Spectator Ions: ions in solution that appear unchanged on both sides of the equation Net Ionic Equation: equations which show only the species that actually participate in the reaction Spectator ions are omitted from the net ionic equation

Write the Net Ionic Equation for: Ag+ (aq) + NO3- (aq) + Na+ (aq) + Cl- (aq) → AgCl(s) + Na+ (aq) + NO3-(aq)

Write the molecular, complete ionic and net ionic equations for the following: lead (II) nitrate reacts with lithium chloride.

Write the molecular, complete ionic and net ionic equations for the following: Hydrobromic acid reacts with calcium hydroxide

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