Chemical Reactions
Acids and Bases Acids: Form hydrogen ions (H + ) when dissolved in water. HCl (aq) H + (aq) + Cl - (aq) Examples: HCl (hydrochloric acid), HNO 3 (nitric acid), H 2 SO 4 (sulfuric acid), HC 2 H 3 O 2 (acetic acid) Bases: Form hydroxide ions (OH - ) when dissolved in water. Mg(OH) 2(aq) Mg 2+ (aq) + OH - (aq) Examples: Group 1 and 2 hydroxides: LiOH, NaOH, Mg(OH) 2, Ca(OH) 2
Types of Reactions There are five types of chemical reactions we observed in the lab: 1. Synthesis reactions 2. Decomposition reactions 3. Single replacement reactions 4. Double replacement reactions 5. 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 1. Identify the type of reaction 2. Predict the product(s) using the type of reaction as a model 3. Balance it Don t forget about the diatomic elements! For example, Oxygen is O 2 as an element.
Guidelines for Predicting the Products of Selected Types of Chemical Reactions Page 6 or 7 on Reference Sheet
1. Synthesis reactions Occur when two substances combine and form a compound. A + B AB Example: 2H 2 + O 2 2H 2 O Example: Mg + O MgO Example: C + O 2 CO 2
Practice Predict the products. Write and balance the following synthesis reaction equations. Na (s) + Cl 2(g) Mg (s) + F 2(g) Na 2 O (s) + H 2 O (g) Al (s) + F 2(g)
2. Decomposition Reactions Occur when a compound breaks up into the elements or simpler compounds AB A + B Example: 2 H 2 O 2H 2 + O 2 Example: 2 HgO 2Hg + O 2
Decomposition Exceptions Carbonates and chlorates are special case decomposition reactions that do not go to the elements. Carbonates (CO 3 2- ) decompose to carbon dioxide and a metal oxide Example: CaCO 3 CO 2 + CaO Hydrogen carbonates decompose to carbon dioxide, a metal oxide, and water Example: 2NaHCO 3 Na 2 O + 2CO 2 + H 2 O Chlorates (ClO 3- ) decompose to oxygen gas and a metal chloride Example: 2 Al(ClO 3 ) 3 2 AlCl 3 + 9 O 2
Practice Predict the products. Then, write and balance the following decomposition reaction equations: Solid Lead (IV) oxide decomposes PbO 2(s) Aluminum nitride decomposes AlN (s) Calcium hydroxide decomposes Ca(OH) 2
Practice Identify the type of reaction for each of the following synthesis or decomposition reactions, and write the balanced equation: N 2(g) + O 2(g) Nitrogen monoxide BaCO 3(s) Co (s) + S (s) NI 3(s) HClO 4 (acid) (make Co be +3)
3. Single Replacement Reactions Occur when one element replaces another in a compound. 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 H 2 O splits into ions, it splits into H + and OH - (not H+ and O -2!!)
Single Replacement Reactions Predict the products. Then, write and balance the following decomposition reaction equations: Zn (s) + HCl (aq) Al (s) + Cu(NO 3 ) 2(aq)
4. Double Replacement Reactions Occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound AB + CD AD + CB
Double Replacement Reactions Think about it like foil ing in algebra, first and last ions go together + inside ions go together Example: AgNO 3(aq) + NaCl (s) AgCl (s) + NaNO 3(aq) Another example: K 2 SO 4(aq) + Ba(NO 3 ) 2(aq) 2 KNO 3(aq) + BaSO 4(s)
Practice Predict the products. Balance the equation 1. HCl (aq) + AgNO 3(aq) 2. CaCl 2(aq) + Na 3 PO 4(aq) 3. Pb(NO 3 ) 2(aq) + BaCl 2(aq) 4. FeCl 3(aq) + NaOH (aq) 5. H 2 SO 4(aq) + NaOH (aq) 6. KOH (aq) + CuSO 4(aq) 7. Mg (s) + H 2 O
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: C x H y + O 2 CO 2 + H 2 O Products in combustion are ALWAYS carbon dioxide and water. (although incomplete burning does cause some byproducts like carbon monoxide)
Combustion Reactions Edgar Allen Poe s drooping eyes and mouth are potential signs of CO poisoning.
Mixed Practice State the type, predict the products, and balance the following reactions: 1. BaCl 2 + H 2 SO 4 2. C 6 H 12 + O 2 3. Zn + CuSO 4 4. Cs + Br 2 5. FeCO 3
Activity Series of Metals Metals listed in order of decreasing activity. Example: Zinc (Zn) can replace Pb in PbCl 2, but Lead (Pb) cannot replace Zn in ZnCl 2.
Activity Series of Halogens Halogens listed in order of decreasing activity. Example: Fluorine (F 2 ) can replace Cl in NaCl, but Chlorine (Cl 2 ) cannot replace F in NaF.
Practice Write the products of each reaction. If no reaction occurs, write N.R. Br 2(aq) + NaI (aq) Br 2(aq) + NaCl (aq) Fe (s) + Pb(NO 3 ) 2(aq) Cl 2(aq) + NaI (aq) Ca (s) + H 2 O (l) Cu (s) + HCl (aq)
Total Ionic Equations for Double Replacement Reactions 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 what compounds dissolve in water. If the compound is soluble (does dissolve in water), then splits the compound into its component ions If the compound is insoluble (does NOT dissolve in water), then it remains as a compound
Solubility Table Page 6 or 7 on Reference Tables
Total Ionic Equations Molecular Equation: 2KCl+ Pb(NO 3 ) 2 PbCl 2 + 2KNO 3 Soluble Soluble Insoluble Soluble Total Ionic Equation: 2 K + + Cl - + Pb +2 + 2 NO 3 - PbCl 2(s) + 2 K + + 2 NO 3 -
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 Total Ionic Equation: 2 K + + 2Cl - + Pb +2 + 2 NO 3 - PbCl 2(s) + 2 K + + 2 NO 3 - Net Ionic Equation: 2Cl - + Pb +2 PbCl 2(s)
Net Ionic Equations Try this one! Write the molecular, total ionic, and net ionic equations for this reaction: Calcium bromide reacts with sodium carbonate in hot water. Molecular: Total Ionic: Net Ionic: