TYPES OF Reactions

Reactions can be categorized on the basis of: Heat changes- exothermic/ endothermic Reactants and products- 5 types Reduction and oxidation (REDOX)- transfer of electrons.

Types of Reactions There are five types of chemical reactions we will talk about: Synthesis reactions _____________ reactions Single displacement reactions ________________ reactions Combustion reactions You need to be able to identify the type of reaction and predict the product(s)

Steps to Writing Reactions Some steps for doing reactions Identify the type of reaction Predict the product(s) using the type of reaction as a model Balance it Don’t forget about the diatomic elements! (BrINClHOF) For example, Oxygen is O2 as an element. In a compound, it can’t be a diatomic element because it’s not an element anymore, it’s a compound!

1. Synthesis reactions Synthesis reactions occur when two substances (generally elements) combine and form a compound. (Sometimes these are called combination or addition reactions.) reactant + reactant  1 product Basically: A + B  AB Example: 2H2 + O2  2H2O Example: C + O2  CO2

Synthesis Reactions Here is another example of a synthesis reaction

Practice Predict the products. Write and balance the following synthesis reaction equations. Sodium metal reacts with chlorine gas Na(s) + Cl2(g)  Solid Magnesium reacts with fluorine gas Mg(s) + F2(g)  Aluminum metal reacts with fluorine gas Al(s) + F2(g) 

2. Decomposition Reactions Decomposition reactions occur when a compound breaks up into the elements or in a few to simpler compounds 1 Reactant  Product + Product In general: AB  A + B Example: 2 H2O  2H2 + O2 Example: 2 HgO  2Hg + O2

Decomposition Reactions Another view of a decomposition reaction:

Decomposition Exceptions Carbonates and chlorates are special case decomposition reactions that do not go to the elements. Carbonates (CO32-) decompose to carbon dioxide and a metal oxide Example: CaCO3  CO2 + CaO Chlorates (ClO3-) decompose to oxygen gas and a metal chloride Example: 2 Al(ClO3)3  2 AlCl3 + 9 O2 There are other special cases, but we will not explore those in Chemistry I

Practice Predict the products. Then, write and balance the following decomposition reaction equations: Solid Lead (IV) oxide decomposes PbO2(s)  Aluminum nitride decomposes AlN(s) 

Practice N2(g) + O2(g)  BaCO3(s)  Co(s)+ S(s)  Nitrogen monoxide Identify the type of reaction for each of the following synthesis or decomposition reactions, and write the balanced equation: N2(g) + O2(g)  BaCO3(s)  Co(s)+ S(s)  NH3(g) + H2CO3(aq) (NH4)2CO3 NI3(s) N2 +I2 Nitrogen monoxide (Co is +3)

Practice p 292 Aluminum oxide decomposes when electricity passes through it. Nickel (II) hydroxide decomposes to produce nickel (II) oxide and water. Heating sodium hydrogen carbonate produces sodium carbonate and water. Carbon dioxide gas is also produced.

3. Single Replacement Reactions Single Replacement Reactions occur when one element replaces another in a compound. A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-). element + compound product + product A + BC  AC + B (if A is a metal) OR A + BC  BA + C (if A is a nonmetal) (remember the cation always goes first!) When H2O splits into ions, it splits into H+ and OH- (not H+ and O-2 !!)

A more reactive metal will replace a less reactive metal from a compound. The Activity series of metals lists metals in order of reactivity (p 293) and helps decide whether or not the reaction will occur.

Single Replacement Reactions Another view:

Activity series of metals lithium, potassium, strontium, calcium sodium , magnesium, aluminum zinc, chromium ,iron, cadmium cobalt, nickel, tin, lead HYDROGEN antimony, arsenic, bismuth, copper mercury Silver, paladium platinum gold

Single Replacement Reactions Write and balance the following single replacement reaction equation: Zinc metal reacts with aqueous hydrochloric acid Zn(s) + HCl(aq)  ZnCl2 + H2(g) Note: Zinc replaces the hydrogen ion in the reaction 2

Single Replacement Reactions Sodium chloride solid reacts with fluorine gas NaCl(s) + F2(g)  NaF(s) + Cl2(g) Note that fluorine replaces chlorine in the compound Aluminum metal reacts with aqueous copper (II) nitrate Al(s)+ Cu(NO3)2(aq) 2 2

Practice p 295 Predict whether the following reactions will occur. If a reaction occurs, write a balanced equation for the reaction. K(s)+ZnCl2(aq)--> Cl2(g)+HF(aq)--> Fe(s)+Na3PO4(aq)--> Al(s)+Pb(NO3)2(aq)-->

4. Double Replacement Reactions Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound Compound + compound  product + product (insoluble product= precipitate) AB + CD  AD + CB

Double Replacement Reactions First and last ions go together + inside ions go together Example: AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq) Another example: K2SO4(aq) + Ba(NO3)2(aq)  KNO3(aq) + BaSO4(s) 2

Practice Predict the products. Balance the equation HCl(aq) + AgNO3(aq)  CaCl2(aq) + Na3PO4(aq)  Pb(NO3)2(aq) + BaCl2(aq)  FeCl3(aq) + NaOH(aq)  H2SO4(aq) + NaOH(aq)  KOH(aq) + CuSO4(aq) 

5. Combustion Reactions Combustion reactions occur when a hydrocarbon reacts with oxygen gas. This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”: 1) A Fuel (hydrocarbon) 2) Oxygen to burn it with 3) Something to ignite the reaction (spark)

Combustion Reactions In general: CxHy + O2  CO2 + H2O Products in combustion are ALWAYS carbon dioxide and water. (although incomplete burning does cause some by-products like carbon monoxide) Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C8H18)

Combustion Reactions Edgar Allen Poe’s drooping eyes and mouth are potential signs of CO poisoning.

Combustion Example C5H12 + O2  CO2 + H2O Write the products and balance the following combustion reaction: C10H22 + O2  8 5 6

Mixed Practice State the type, predict the products, and balance the following reactions: BaCl2 + H2SO4  C6H12 + O2  Zn + CuSO4  Cs + Br2  FeCO3 

TYPES OF REACTIONS review 1. NAME THE 5 TYPES OF REACTIONS AND GIVE AN EXAMPLE OF EACH. (10 pts) 2. CATEGORIZE THE FOLLOWING BASED ON REACTION TYPE:(5 pts) A). 2H2 +O2 ---2H2 O B). Cl2 +NaI--2NaCl +I2 C). CH4 +2O2 --CO2 +2H2O D).Ca (OH)2 ---CaO + H2O E). NaOH + KCl KOH + NaCl

3. WHICH CONDITION HAS TO BE FULFILLED IN ORDER FOR A SINGLE DISPLACEMENT REACTION TO OCCUR?(1 pt) 4. NAME THE TWO COMMON PRODUCTS OF COMBUSTION REACTIONS.(1 pt) 5. Fill in the blanks with the correct products of this reaction, and balance the equation:(2pts) PbCl2 + Na2SO4 --> ____ + _______

Acids + Bases Acids all contain H+ cations and an anion. Bases all contain OH- anions and a cation, except for weak bases such as NH3 When acids dissociate in water they release H+ ions and their anions. When bases dissociate in water they release or form OH- ions and their cations.

Neutralization Reactions In the reaction of an acid with a base, the H+ from the acid combines with the OH- from the base to make water The cation from the base combines with the anion from the acid to make the salt acid + base salt + water H2SO4(aq) + Ca(OH)2(aq)  CaSO4(aq) + 2 H2O(l) The net ionic equation for a strong acid-strong base reaction is always H+ (aq) + OH- (aq)  H2O(l)

Neutralization practice P 195 Q 39- Complete and balance the following neutralization reactions. Underline the salt - A. HCl + KOH--> RbOH + HNO3 --> HClO4+NaOH--> HBr+CsOH-->

Reactions of Metals with Nonmetals (Oxidation-Reduction) The metal loses electrons and becomes a cation (oxidation) The nonmetal gains electrons and becomes an anion (reduction) In the reaction, electrons are transferred from the metal to the nonmetal

Oxidation-Reduction Reactions Oxidation-reduction reactions: reactions that involve a transfer of one or more electrons The substance that loses electrons in the reaction is oxidized. The substance that gains electrons in the reaction is reduced.

Another Kind of Oxidation-Reduction Reaction Some reactions between two non-metals are also oxidation-reduction reaction. Any reaction in which O2 is a reactant or a product will be an oxidation-reduction reaction. CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g) 2 SO3(g)  2 SO2(g) + O2(g)

Self check p 183 For each reaction, show how electrons are gained and lost. A. 2Na(s)+ Br2(l)--> 2NaBr(s) B. 2Ca(s)+ O2(g)--> 2CaO(s) P 196 Q 49- Balance each redox reaction. In each, indicate which substance is being oxidized and which is being reduced- A. Na + S--> Na2S B. Mg +O2-->MgO C. Ca +F2--> CaF2 Fe +Cl2-->FeCl3

Total Ionic Equations Once you write the molecular equation (synthesis, decomposition, etc.), you should check for reactants and products that are soluble or insoluble. We usually assume the reaction is in water We can use a solubility table to tell us which compounds dissolve in water. If the compound is soluble (does dissolve in water), then split the compound into its component ions If the compound is insoluble (does NOT dissolve in water), then it remains as a compound

Kinetic Molecular Theory (KMT) - molecules need to collide in order to react! - collisions happen faster in fluids (liquids/ gases) -which is why we need to determine solubility!

Solubility Table

Solubilities Not on the Table! Gases only slightly dissolve in water Strong acids and bases dissolve in water Hydrochloric, Hydrobromic, Hydroiodic, Nitric, Sulfuric, Perchloric Acids Group I hydroxides (should be on your chart anyway) Water slightly dissolves in water! (H+ and OH-) SrSO4 is insoluble; BeI2 and the products are soluble There are other tables and rules that cover more compounds than your table!

Self check p 175 Predict whether a solid will form when the following parts of solutions are mixed. If so, identify the solid and write the balanced equation for the reaction- Ba(NO3)2(aq) and NaCl(aq) Na2S(aq) and Cu(NO3)2(aq) NH4Cl(aq) and Pb(NO3)2(aq)

Total Ionic Equations Molecular Equation: K2CrO4 + Pb(NO3)2  PbCrO4 + 2 KNO3 Soluble Soluble Insoluble Soluble Total Ionic Equation: 2 K+ + CrO4 -2 + Pb+2 + 2 NO3-  PbCrO4 (s) + 2 K+ + 2 NO3-

Net Ionic Equations These are the same as total ionic equations, but you should cancel out ions that appear on BOTH sides of the equation (termed as spectator ions) Total Ionic Equation(complete): 2 K+ + CrO4 -2 + Pb+2 + 2 NO3-  PbCrO4 (s) + 2 K+ + 2 NO3- Net Ionic Equation: CrO4 -2 + Pb+2  PbCrO4 (s)

Net Ionic Equations Try this one! Write the molecular, total ionic, and net ionic equations for this reaction: Silver nitrate reacts with Lead (II) Chloride in hot water. Molecular: Total Ionic: Net Ionic:

Self check p 177 For each of the following reactions, write the molecular equation, the complete ionic equation, and the net ionic equation. Aqueous sodium sulfide is mixed with aqueous copper (II) nitrate to produce solid copper (II) sulfide and aqueous sodium nitrate. Aqueous ammonium chloride and aqueous lead (II) nitrate react to form lead (II) chloride and aqueous ammonium nitrate.

Study guide for balancing equations- Chapter 6 Basic structure of equations- reactants, products, arrow, physical state. Signs of a chemical change. Law of conservation of matter. Rules for balancing equations. Balancing equations.

Study guide for Types of reactions and net ionic equations- Chapter 7 types of reactions- definitions, examples, identification – synthesis, decomposition, single and double displacement, combustion, neutralization and redox! net ionic equations- solubility, cancelling ions, spectator ions