CHEMICAL REACTIONS

1. CHEMICAL REACTIONS 0 Reactants: Zn + I2 Product: Zn I2

2. Introduction 0 • Chemical reactions occur when • Chemical reactions involve • changes in the___________________________ (the making of new materials with new properties) • ___________________changes • Symbols represent elements • Formulas describe compounds • Chemical equations describe a chemical reaction

3. 0 Types of Chemical Reactions (rxns.)

4. Types of Reactions 0 • Reactions are classified by their products. • There are five types of chemical reactions we will talk about: • You need to be able to identify the type of reaction and predict the product(s)

5. Steps to Writing Reactions 0 Some steps for doing reactions: • Identify the • Predict the product(s) using the • Balance it Don’t forget about the diatomic elements! (_________________) For example, Oxygen is O2 as anelement. In a compound, it can’t be a diatomic element because it’s not an element anymore, it’s a compound!

6. Synthesis Reactions 0 • Synthesis (meaning to make) are • Also called • Direct combination or combination reactions • Addition reactions • typified by their _________________________________________. • If you have a reaction in which at least 2 elements or compounds are reacted and produce a single product, the reaction is a synthesis reaction.

7. Synthesis reactions 0 • Synthesis reactions are sometimes called ________________________________________. reactant + reactant  1 product • Basically: A + B  AB • Example: 2H2 + O2  2H2O • Example: C+ O2  CO2 • Note: Single Product! This is your clue that this is a synthesis or combination reaction.

8. Synthesis Reactions 0 • Here is another example of a synthesis reaction

9. Examples of Synthesis Reactions • 2Na + S Na2S • This one is an example of two elements in atomic form (Na and S) combining to form a compound (sodium sulfide). • 2H2 + O2 2H2O • In this example, A and B are two elements in molecular form (hydrogen and oxygen molecules), and the product is water, which is simply the chemical combination of hydrogen and oxygen.

10. Examples of Synthesis Reactions • 2Fe + O2 • In this example, substance “A” is an element in atomic form (Fe), and substance “B” is an element in molecular form (O2). The result is a direct chemical combination of the two elements (FeO, iron oxide, which is “rust”). • CuO + H2O • This is an example where both substances going into the reaction are molecules. The result is what you get when you “add” all of the atoms in the reaction together.

11. Practice 0 • 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) 

12. Decomposition Reactions 0 Decomposition reactions are really ______________ ________________ ____________. Remember, if you can make a substance, you should be able to break it back apart into its components. A good way to remember decomposition reactions to to remember what happens when something decomposes. It falls apart!

13. Decomposition Reactions 0 • Decomposition reactions occur when a compound __________________________ _____________________________________1 Reactant  Product + Product • Basically: AB  A + B • Example: 2 H2O  • Example: 2 HgO  • Note: Single Reactant! The single reactant is your clue that this is a decomposition reaction.

14. Decomposition Reactions 0 • Another view of a decomposition reaction:

15. Decomposition Exceptions 0 • Carbonates and chlorates are special case decomposition reactions that do not go to the elements. • Carbonates (CO32-) decompose to • Example: CaCO3  • Chlorates (ClO3-) decompose to • Example: 2 Al(ClO3)3  • There are other special cases, but we will not explore those in this class

16. Practice 0 • Predict the products. Then, write and balance the following decomposition reaction equations: • Solid Lead (IV) oxide decomposes PbO2(s)  • Aluminum nitride decomposes AlN(s) 

17. Practice 0 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)  • NI3(s) 

18. Single Replacement Reactions 0 Single replacement reactions occur when one chemical In the typical single replacement reaction,

19. Single Replacement Reactions 0 • Single Replacement Reactions occur when one element replaces another in a compound. • A metal can • OR • 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 !!)

20. Single Replacement Reactions 0 • Another view:

21. The Activity Series 0 • Not all single replacement reactions • This depends upon • Elements above _______ replace elements below; elements below _____________ replace elements above them on the series

22. Single Replacement Reactions 0 • Write and balance the following single replacement reaction equation: • Zinc metal reacts with aqueous hydrochloric acid Note: Zinc replaces the hydrogen ion in the reaction

23. Single Replacement Reactions 0 • Sodium chloride solid reacts with fluorine gas Note that fluorine replaces chlorine in the compound • Aluminum metal reacts with aqueous copper (II) nitrate

24. 4. Double Replacement Reactions 0 Double replacement reactions are identified by

25. Double Replacement Reactions 0 • Double Replacement Reactions occur when a • Compound + compound  product + product • Notice that one ion from compound AB replaces one ion from compound CD.

26. Double Replacement Reactions 0 • Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together • Example: AgNO3(aq) + NaCl(s)  • Another example: K2SO4(aq) + Ba(NO3)2(aq)  2

27. Solubility 0 • For a double replacement reaction to have occurred, • There are rules to determine which of the materials formed is the solid • If no solid is formed, there is said to be

28. Solubility Tables 0 • Solubility tables help determine which materials are soluble in water and which are not • In general, Solubility Rules can be summarized as follows • All compounds containing alkali metal cations and the ammonium ion are soluble. • All compounds containing NO3-, ClO4-, ClO3-, and C2H3O2- anions are soluble. • All chlorides, bromides, and iodides are soluble except those containing Ag+, Pb2+, or Hg22+. • All sulfates are soluble except those containing Hg22+, Pb2+, Sr2+, Ca2+, or Ba2+. • All hydroxides are insoluble except compounds of the alkali metals, Ca2+, Sr2+, and Ba2+. • All compounds containing PO43-, S2-, CO32-, and SO32- ions are insoluble except those that also contain alkali metals or NH4+.

29. Practice 0 • Predict the products. Balance the equation • HCl(aq) + AgNO3(aq)  • Pb(NO3)2(aq) + BaCl2(aq)  • FeCl3(aq) + NaOH(aq)  • H2SO4(aq) + NaOH(aq) 

30. Combustion Reactions 0 Combustion reactions are the ones that burn (or explode!). There are two types of combustion reactions— These reactions are identified by their products. They either produce

31. Complete Combustion Reactions 0 These reactions burn “efficiently” which means they produce _____________and ____________. These reactions typically burn cleanly and leave very little residue behind.

32. 5. Combustion Reactions 0 • Combustion reactions occur when a hydrocarbon reacts with _____________. • This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”:1) • 2) • 3)

33. Combustion Reactions 0 • In general: CxHy + O2  CO2 + H2O • Products in combustion are ALWAYS • (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)

34. Complete Combustion Reactions 0 • CH4 + O2 CO2 + H2O • They may also be written: • Clues: CO2 (carbon dioxide) in the product along with water

35. Combustion 0 • Example • Write the products and balance the following combustion reaction:

36. Incomplete Combustion Reactions 0 Incomplete combustion reactions occur This can cause a lot of harm if the gases produced cannot escape. Carbon monoxide, an odorless and colorless gas, . People poisoned by this gas usually become .

37. Incomplete Combustion Reactions 0 • CH4 + O2 CO + H2O • These reactions may also be written by: • Clue: CO (Carbon monoxide as a product.)

38. Mixed Practice 0 • State the type, predict the products, and balance the following reactions: • BaCl2 + H2SO4 • C6H12 + O2  • Zn + CuSO4  • Cs + Br2  • FeCO3 

39. Predicting Products of Reactions 0 • Completing reactions requires knowledge of the • You must first identify the reaction type by • The only type of reaction that cannot be predicted this way

40. First Step: 0 • Identify reaction type Example: Al + O2 

41. Second Step: 0 • Write the net ionic equation for the reactants

42. Step 3 0 • Using clues, complete reaction taking care to write each formula correctly by checking charges and “criss-crossing” if necessary.

43. Predicting Products of Reactions (cont.) 0 • For Single Replacement reactions, check • Once you write the molecular equation, you should check for reactants and products that are

44. Reactions in Aqueous Solutions 0 • a.k.a. Net Ionic Equations • Molecular Equations: • Does not show what happens on the molecular level • Total (or Complete) Ionic Equations: • Some ions participate in the reaction • Some ions do NOT participate in the reaction-called spectator ions. • Net Ionic Equations: show only the ions that participate in the reaction

45. Writing Total Ionic Equations 0 • 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__________ • We can use a solubility table to tell us what compounds dissolve in water. • If the compound is soluble (does dissolve in water), then splits the compound into its ___________________ • If the compound is insoluble _____________________ then it remains as a compound

46. Writing Total Ionic Equations 0 Molecular Equation: K2CrO4 + Pb(NO3)2 PbCrO4 + 2 KNO3 Total Ionic Equation:

47. Net Ionic Equations 0 • These are the same as total ionic equations, but you should cancel out ions that appear on BOTH sides of the equation Total Ionic Equation: Net Ionic Equation:

48. Net Ionic Equations 0 • 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. AgNO3 + PbCl2 Molecular: 2 AgNO3 + PbCl2 2 AgCl + Pb(NO3)2 Total Ionic: 2 Ag+ + 2 NO3- + Pb+2 + 2 Cl-  2 AgCl (s) + Pb+2 + 2 NO3- Net Ionic:

49. Acid-Base Reactions 0 • Acid: • Base: • The reaction ALWAYS forms water and an ionic compound(mostly aqueous, known as a salt). • The actual definition of a _______is the ionic product of an acid-base neutralization reaction)

50. Acid-Base Neutralization • Chemically the reaction looks like this: Acid + Base Salt + Water • A classic example: HCl + NaOH NaCl + H2O