Chemical Reactions Created by: Jana Perkins Hernando High School Ch 11
Objectives 4.a.3. (Science - Grade(s): 9-12) Building blocks of matter (e.g., proton, neutron, and electron) and elementary particles (e.g., positron, mesons, neutrinos, etc.) 3.c.1. (Science - Grade(s): 9-12) Single displacement, double displacement, synthesis (combination), decomposition, disproportionation, combustion, or precipitation. 3.c.2. (Science - Grade(s): 9-12) Products (given reactants) or reactants (given products) for each reaction type 4.e.2. (Science - Grade(s): 9-12) Chemical reaction rates affected by temperature, concentration, surface area, pressure, mixing, and the presence of a catalyst
Key Terms Chemical equation Skeleton equation Catalyst Coefficients Balanced equation Reactants Products
Chemical Reactions in Everyday Life
Reactants à Products Word Equations Reactants and products are separated by + signs Chemical substances are expressed in name form Ex: Iron + oxygenà Iron (III) oxide Reads: Iron reacts with oxygen to produce iron 3 oxide
Chemical Reactions Reactants à Products Reactants are on the left of the arrow Products are on the right of the arrow Arrow = yields, gives, reacts to produce
Reactants and Products
Chemical Equations Representation of a chemical reaction Fe + O 2 à Fe 2 O 3 {RUST} Skeleton Equation: is a chemical equation that does not indicate the relative amounts of the reactants and products. Fe + O 2 à Fe 2 O 3 Not balanced 1 iron, 2 oxygens! 2 irons, 3 oxygens
Chemical Equations Symbols Symbols used in chemical equations: + : separates reactants or products à : yeilds ; separates reactants from products (s): solid (l): liquid (g): gas (aq): aqueous; substance is dissolved in water : heat applied
Understanding a Written Equation 4Fe + 3O 2 à 2Fe 2 O 3 Coefficients: small whole numbers that are placed in front of formulas in equation in order to balance it Balanced equation: each side of the equation has the same number of atoms of each element (mass conserved)
Quiz Questions 1) Which side of the reaction would you find the product? 2) Which side of the reaction would you find the reactants? 3) How do you show heat applied to a reaction?
Law of Conservation of Mass
Balancing Equations H 2 + O 2 à H 2 O Unbalanced 2 H 2 H 2 O 1 O H 2 + O 2 à H 2 O 2 H 2 + 1 O 2 à 2 H 2 O 4 H 4 H 2 O 2 O
Balancing Rules (1-3) 1. Determine the correct formulas for all the reactants and products. 2. Write the skeleton equation. (Reactants on left, products on right, yield sign in between. If two or more reactants/products are involved, separate their formulas with plus signs. 3. Determine the number of atoms of each element in the reactants and products. (Count polyatomic ion as a single unit if it appears unchanged on both sides of the equation)
Balancing Rules (4-6) 4. Balance the elements one at a time by using coefficients. When no coefficient is written, it is assumed to be 1. Begin by balancing elements that appear only once on each side of the equation. Never balance an equation by changing the subscripts in a chemical formula. Each substance has only one correct formula. 5. Check each atom or polyatomic ion to be sure they are equal on both sides of the equation. 6. Make sure all the coefficients are in the lowest possible ratios.
Balancing Practice ZnO à Zn + O 2 S + O 2 à SO 3 C 3 H 8 + O 2 à CO 2 + H 2 O Be + O 2 à Be 2 O S 8 + O 2 à SO 2
Balancing Practice Na + H 2 O à NaOH + H 2 C 7 H 6 O 2 + O 2 à CO 2 + H 2 O K 2 O + H 2 O à KOH Al 2 (SO 4 ) 3 + Ca(OH) 2 à Al(OH) 3 + CaSO 4 Al + HCl à AlCl 3 + H 2
Quiz Questions 1) What do you call an unbalanced equation? 2) When using coefficients to balance, what is the applied function to the subscripts: Multiply, divide, add, subtract? 3) Why can subscripts not be changed when balancing an equation? 4) Why must equations be balanced?
Chemical Reactions The 5 Basic Classifications
Combination reaction Decomposition reaction Single-replacement reaction Activity series Double-replacement reaction Combustion reaction Key Terms
Types of Reactions
Reaction Checklist 1) Is O 2 a reactant? (combustion) 2) One product? (synthesis) 3) One reactant? (decomposition) 4) Is an element being replaced? (single) 5) 2 switches? (double)
SYNTHESIS two or more elements or compounds may combine to form a more complex compound. AKA: composition or combination General Equation A + B! AB
Synthesis Reactions Complete and balance this equation for a synthesis reaction: Be + O 2 à 2Be + 1O 2 à 2BeO Write and balance the equation for the formation of magnesium nitride (Mg 3 N 2 ) from its elements. à 1Mg 3 N 2 3Mg + 1N 2 à 1Mg 3 N 2
Synthesis Reaction Metal + oxygen metal oxide Nonmetal + oxygen Metal oxide + water nonmetallic oxide metallic hydroxide Nonmetallic oxide + water acid Metal + nonmetal salt A few nonmetals combine with each other.
Decomposition Reaction A single compound breaks down into its component parts or simpler compounds. General Equation AB ---> A + B
Decomposition Reaction Metallic carbonates, when heated, form metallic oxides and CO 2(g). Most metallic hydroxides, when heated, decompose into metallic oxides and water. Metallic chlorates, when heated, decompose into metallic chlorides and oxygen. Some acids, when heated, decompose into nonmetallic oxides and water. Some oxides, when heated, decompose. Some decomposition reactions are produced by electricity.
Single Replacement a more active element takes the place of another element in a compound and sets the less active one free. General Equation: A + BX à AX + B
Single Replacement Replacement of a metal in a compound by a more active metal. Replacement of hydrogen in water by an active metal. Replacement of hydrogen in acids by active metals. Replacement of nonmetals by more active nonmetals.
Single Replacement Activity Series of Metals Refer to the activity series for metals and nonmetals to predict products of replacement reactions. If the free element is above the element to be replaced in the compound, then the reaction will occur. If it is below, then no reaction occurs.
Activity Series of Metals
Double Replacement/ Ionic Occurs between ions in aqueous solution. A reaction will occur when a pair of ions come together to produce at least one of the following: a precipitate a gas water or some other non-ionized substance. general form: AB + CD----> AD + CB
Double Replacement Formation of precipitate. Formation of a gas Formation of water. (If the reaction is between an acid and a base it is called a neutralization reaction.) Formation of a product which decomposes.
What Is Combustion?
What Is Combustion? One or more reactants combine with oxygen releasing heat or light Must include the reactant oxygen, O 2 General Equation 1& 2: 1)A + O 2! AO Example 1: 2Mg(s) + O 2 (g) 2MgO(s) 2)Hydrocarbon + O 2! H 2 O + CO 2 + Energy Example 2: CH 4 + O 2 H 2 O + CO 2
T. Trimpe http://sciencespot.net/
Watch the movie and then complete the chart. Type of Reaction Synthesis Definition Two or more elements or compounds combine to make a more complex substance Chemical Reactions «Equation A + B AB Decomposition Compounds break down into simpler substances AB A + B Single Replacement Double Replacement Occurs when one element replaces another one in a compound Occurs when different atoms in two different compounds trade places AB + C AC + B AB + CD AC + BD A = Red B = Blue C = Green D = Yellow
Identifying Chemical Reactions 2. Use colored pencils to circle the common atoms or compounds in each equation to help you determine the type of reaction it illustrates. Use the code below to classify each reaction. S = Synthesis D = Decomposition SR = Single Replacement DR = Double Replacement P + O 2 P 4 O 10 Mg + O 2 MgO HgO Hg + O 2 Al 2 O 3 Al + O 2 Cl 2 + NaBr NaCl + Br 2 H 2 + N 2 NH 3
Na + Br 2 NaBr CuCl 2 + H 2 S CuS + HCl HgO + Cl 2 HgCl + O 2 C + H 2 CH 4 KClO 3 KCl + O 2 S 8 + F 2 SF 6 BaCl 2 + Na 2 SO 4 NaCl + BaSO 4
s=synthesis d=decomposition sr=single replacement dr=double replacement c=combustion 1. P + O 2 P 4 O 10 2. Mg + O 2 MgO 3. HgO Hg + O 2 4. Al 2 O 3 Al + O 2 5. Cl 2 + NaBr NaCl + Br 2 6. H 2 + N 2 NH 3 7. Na + Br 2 NaBr 8. CuCl 2 + H 2 S CuS + HCl 9. HgO + Cl 2 HgCl + O 2 10. C + H 2 CH 4 11. KClO 3 KCl + O 2 12. S 8 + F 2 SF 6 13. HgO + Cl 2 HgCl + O 2 14. C + H 2 CH 4 15. BaCl 2 + Na 2 SO 4 NaCl + BaSO 4
QUIZ Balance equations and differentiate the types. 1. C + H 2 CH 4 2. HgO à Hg + O 2 3. Be + O 2 à Be 2 O 4. HgO + Cl 2 HgCl + O 2 5. H 2 + N 2 NH 3 BONUS: BaCl 2 + Na 2 SO 4 NaCl + BaSO 4
Citations Indicators in Reactions. Sunburst Visual Media. 2001 Learn360. 14 April 2015 http://www.learn360.com/showvideo.aspx? IPK=98211979&ID=150371 Chemical Reactions. Films for the Humanities & Sciences. 2010 Learn360. 20 April 2015 http://www.learn360.com/showvideo.aspx? IPK=98211979&ID=929307