Types of Chemical Reactions Thermite reaction
Types of Reactions • There are five types of chemical reactions we will talk about: • Synthesis reactions • decomposition reactions • Single replacement reactions • Double replacement 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
Reminder! • Don’t forget about the diatomic elements! For example, Oxygen is O2 as anelement. • In a compound, (MgO) 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 (generallyelements) combine and form a compound. (Sometimes these are called combination or addition reactions.)
SYNTHESIS GENERAL FORMULA 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 into a few simpler compounds
DecompositionGENERAL FORMULA • 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 are a special case of a decomposition reaction that does not go to the elements. • Carbonates (CO32-) decompose to carbon dioxide and a metal oxide • Example: CaCO3 CO2 + CaO • There are other special cases, but we will not explore those in High School Chemistry
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 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) (Nitrogen monoxide) (Co+3)
Warm-Up • Sodium metal reacts with water to produce aqueous sodium hydroxide and hydrogen gas. Write the balanced equation for this reaction. • 2Na(g) + 2H2O(l) 2NaOH(aq) + H2(g) • Balance the equation • C6H14 + O2 CO2 + H2O • 2C6H14 + 19O2 12CO2 + 14H2O
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 (-).
Single ReplacementGeneral Formula • element + compound product + product A + BC AC + B (if A is a metal) CATIONIC OR A + BC BA + C (if A is a nonmetal) ANIONIC (remember the cation always goes first!) When H2O splits into ions, it splits into H+ and OH- (not H+ and O-2 !!)
Single Replacement Reactions • Another view:
Trade-off lab • __Al(s) + __CuCl2(aq) → __AlCl3(aq) + __Cu(s) • What type of reaction was the trade-off lab? • Single Replacement Reaction • Is it cationic or anionic replacement? • General form: • A + BC → AC + B
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 Is it cationic or anionic? Cationic 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 • Cationic or Anionic? • Anionic 2 2
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
Double ReplacementGeneral Formula • compound + compound product + product • AB + CD AD + CB
Double Replacement Reactions • Think about it like “foil”ing in algebra, outside 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
Group Quiz • Demo • On a clean piece of paper, write both group members names • Speculate as to why specks of solid are forming. One paragraph. • Turn it into your folder
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)
Warm Up • Predict the Products and write the net ionic equation for the following reactions • KI (aq) + Pb(NO3)2(aq) → • A solution of calcium hydroxide is added to a solution of potassium sulfate
Total Ionic Equations • Once you write the molecular equation (Double replacement), you should check for reactants and products that are soluble or insoluble. • We assume double replacement reactions are in water • We can use a solubility table to tell us what compounds dissolve in water. • If the compound is soluble (dissolves in water), then it splits the compound into its component ions • If the compound is insoluble (does NOT dissolve in water), then it remains as a compound and the phase label is (s).
Solubility Trends • Gases only slightly dissolve in water • Treat as insoluble • Water slightly dissolves in water (H+ and OH-) • Treat as insoluble • Strong acids and bases dissolve in water • Hydrochloric, Hydrobromic, Hydroiodic, Nitric, Sulfuric, Perchloric Acids • Group I hydroxides
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 Total Ionic Equation: 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:
5. Combustion Reactions • Combustion reactions occur when an element 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 2) Oxygen to burn it with3) Something to ignite the reaction (spark)
Combustion Reactions • In general: Hydrocarbon+ O2 CO2 + H2O Or Element + O2 element oxide • Products in combustion are ALWAYS carbon dioxide and water or an oxide
4th Period brainteaserClassify, Predict Products (if necessary), & balance • BaCl2(aq) + H2SO4(aq) • C6H12 + O2(g) • Zn(s) + CuSO4(aq) • K(s) + Br2(g) KBr(s) • H2O2(aq) O2(g) + H2O(l) • Na(s) + O2(g)
Combustion Reactions Edgar Allen Poe’s drooping eyes and mouth are potential signs of CO poisoning. CO is a by-product of the combustion process if the hydrocarbon does not fully combust.
Combustion • Example • C5H12 + 8O2 5CO2 + 6H2O • Write the products and balance the following combustion reaction: • C4H10 + O2
Activity Series of Metals • Matter tends to react in such a way that more reactive substances form less reactive substances. Some metals are higher in reactivity than others • Activity series: a list of metals arranged in decreasing reactivity (used for metal and hydrogen single replacement reactions) 42
5th period Warm-upClassify, Predict Products (if necessary), & balance • BaCl2(aq) + H2SO4(aq) • C6H12 + O2(g) • Zn(s) + CuSO4(aq) • K(s) + Br2(g) KBr(s) • H2O2(aq) O2(g) + H2O(l) • Na(s) + O2(g) I will go over the warm-up later in the period.
On a blank piece of paper… • Write one thing you know about chemical equations. • Write one thing you need to know but struggle with about chemical equations
Activity Series • The higher the metal on the activity series, the more active that metal. • Translation: higher metals on the chart will form ions in solution (dissolve in water…ie. Aqueous) the other metal in the reaction will precipitate (solid) • Use the activity series on the back of periodic table to predict products and assign phase labels
Predict whether a reaction occursIf a reaction occurs, predict the products. (don’t forget phase labels) • Na (s) + H2O (l)→ • Fe (s) + HCl (aq)→ • Fe (s) + Cr(NO3)3(aq) → • Ni (s) + Pb(NO3)2(aq) → • Ag (s) + Mg(NO3)2(aq) → • Zn (s) + Co(NO3)2(aq) →
Summary of Reactions • For the test • You should be able to …. • Classify reactions • Predict Products • Write balanced molecular equations • Write balanced net ionic equations
Synthesis and Decomposition • General forms: • Synthesis A + B → AB • Decomposition AB → A + B • If you can’t see the general form of a reaction try labeling the reactants and products with “A” and “B”. • Know how to classify these reactions
Combustion • Memorize the two general forms Hydrocarbon+ O2(g) CO2(g) + H2O(l) Element + O2(g) element oxide • Balancing the first general form can be tricky….. Just keep working at it. • You must be able to classify and predict products in these reactions.
Single Replacement • Use the Activity series on the back of your periodic table to determine whether a reaction occurs. • If a reaction occurs, predict products and balance….don’t forget phase labels. • Classify as cationic or anionic • General form: • A + BC → AC + B (cationic) Or • A + BC → BA + C (anionic)
Double Replacement • Predict products • Use your Solubility Rules (pg 178) to determine whether a reaction occurs. • If a reaction occurs, determine phases of products • Determine the Net ionic equation if asked to do so. • General Form: • AB + CD → AD + CB
From Warm-up • BaCl2(aq) + H2SO4(aq) • C6H12 + O2(g) • Zn(s) + CuSO4(aq) • K(s) + Br2(g) KBr(s) • H2O2(aq) O2(g) + H2O(l) • Na(s) + O2(g)
Demo Gas Collection • In your pairs, the person with the longest eyelashes go get your lab books on the back table. • Technique for collecting gas via water displacement • First reaction • Zinc metal is placed in a jar. Hydrochloric acid is added to the jar • Write the chemical equation for this reaction and classify it.