Chapter 10 Chemical Reactions

Section 10.1  Reactions & Equations Chemical reaction—process by which the atoms of 1 or more substances are rearranged to form different substances Evidence of chemical reactions: (fig 10.1) Temperature change—release energy in the form of heat & light Color change Odor is detectable Gas bubbles Appearance of a solid (precipitate)

Section 10.1  Reactions & Equations Reactants—starting substances Products—substances formed during reaction An arrow () separates products from reactants. You would read the arrow as “react to produce” or “yield.”

Section 10.1  Reactions & Equations Physical states of matter are shown in parentheses. (s) = solid (l) = liquid (g) = gas (aq) = aqueous; water solution

Skeleton Equation—use chemical formulas rather than words Word Equation Iron(s) + chlorine(g)  iron(III) chloride(s) Skeleton Equation—use chemical formulas rather than words Fe(s) + Cl2(g)  FeCl3(s)

Work practice problems 1-3. Ex. Solid carbon & solid sulfur(S8) react to form solid carbon disulfide. Work practice problems 1-3.

Practice 1. hydrogen(g) + bromine(g)  hydrobromic acid (aq) 2. carbon monoxide(g) + oxygen(g)  carbon dioxide(g) 3. potassium chlorate(s)  potassium chloride(s) + oxygen(g)

Word & skeleton equations lack important information Word & skeleton equations lack important information. A true chemical equation must show that matter is conserved.

Balancing Chemical Equations Use coefficients—whole # written in front of a formula Do NOT use 1 as a coefficient in balancing. The coefficient represents the lowest whole number ratio. write the skeleton equation. count the atoms of reactants & products one at a time. (count individual elements in polyatomic ions) change the coefficient to make the number of atoms of each element equal on both sides of the arrow **NEVER BALANCE BY CHANGING THE SUBSCRIPTS** **SAVE OXYGEN & HYDROGEN FOR LAST**

Balancing equations Example: N2(g) + H2(g)  NH3(g)

Practice: Balancing equations H2(g) + Br2(g)  HBr(g) CO(g) + O2(g)  CO2(g) KClO3(s)  KCl(s) + O2(g) Carbon & sulfur react to form carbon disulfide.

** Balance…

10.2 Classifying Chemical Reactions 1. SYNTHESIS reaction- two or more substances react to form a single product. A + B  AB Na + Cl2  __________

Example: Synthesis Rxn Mg + N2  Mg+2 N-3  Mg3N2

Practice: Synthesis Rxn __________  CaO Iron (III) + Oxygen  __(formula)____________

10.2 Classifying Chemical Reactions 2. Combustion reaction- O2 combines with a substance often forming CO2 &/or H2O. (Similar to synthesis) H2 + O2  H2O ___ + O2  CO2

Example: Combustion Rxn CH4(g) + O2(g)  CO2(g) + H2O(g)

Practice: Write a balanced equation & determine type of reaction The solids aluminum and sulfur(S8) react to produce solid aluminum sulfide. The gases nitrogen dioxide and oxygen react to produce dinitrogen pentoxide gas. Ethane gas (C2H6) burns in air to produce carbon dioxide gas and water vapor.

10.2 Classifying Chemical Reactions 3. Decomposition reaction- a single compound breaks into 2 or more new compounds. AB  A + B Na3N (s)  __ (s) + __ (g)

Decomposition of sugar

Example: Decomposition Rxn ___________  Hg (l) + O2 (g) assume it is mercury (II)

Practice: Decomposition Rxn Al2O3(s) ________+_______ Aqueous nickel(II) hydroxide decomposes to produce nickel(II) oxide & water. Cu2S  ___________

Classify the reaction Na + O2  Na2O CaO  Ca + O2 Synthesis CaO  Ca + O2 Decomposition CH4 + O2  H2O + CO2 Combustion KClO3  KCl + O2 O2 + C5H12  CO2 + H2O Al + F2  AlF3

Classify the reaction C6H14 + O2  Mg + N2  H2O2  Ag + S  Zn + O2 

4. Single Replacement reaction- an atom replace the atom in a compound. A + BX  AX + B Cu(II) (s) + 2AgNO3 (aq)   ________________

Activity Series: -------------over there

Cu(II) (s) + 2AgNO3 (aq)   ________________

Copper plating

Example: Single replacement Fe(II) (s) + CuSO4(aq)  (Fe+2 + Cu+2 + SO4-2)  FeSO4(aq) + Cu

Practice 2-6 2. Ag(s) + AlPO4(aq)  NR (no reaction) 3. Mg(s) + AlCl3(aq)  MgCl2(aq) + Al(s) 4. K(s) + ZnCl2(aq)  KCl(aq) + Zn(s) 5. Br2(l) + MgCl2(aq)  NR *6. F2(g) + CaCl2(aq) CaF2(aq) + Cl2(g)

5. Double-replacement reaction- Two compounds react to form 2 new compounds. In this reaction water, a gas or a solid can be formed. AX + BY  AY + BX

Double replacement rxn

Example: Double-replacement Rxn Ca(OH)2(aq) + 2HCl(aq)  Ca+2 + OH-1 + H+1 + Cl-1  CaCl2(aq) + 2H2O(l)

Practice: Double Replacement Rxn NaOH(aq) + CuCl2(aq)  Na+1 + OH-1 + Cu+2 + Cl-1  NaCl(aq) + Cu(OH)2(s) KCN(aq) + HBr(aq)  K+1 + CN-1 + H+1 + Br-1  KBr + HCN

Practice:Give the balanced skeletal for the following. 1. Aqueous barium chloride and aqueous potassium carbonate react to produce solid barium carbonate and aqueous potassium chloride. BaCl2(aq) + K2CO3(aq)  BaCO3(s) + 2KCl(aq) 2. Aqueous lithium iodide and aqueous silver(I) nitrate react to produce solid silver(I) iodide and aqueous lithium nitrate. LiI(aq) + AgNO3(aq)  AgI (s) + LiNO3(aq)

Classify each rxn CH4 + O2  H2O + CO2 KClO3(s)  KCl(s) + O2(g) Combustion KClO3(s)  KCl(s) + O2(g) decomposition ZnCl2(aq) + K(s)  KCl(aq) + Zn(s) Single-replacement BaCl2+ K2CO3 BaCO3+ 2KCl Double-replacement CaCl2(aq) + F2(g)  CaF2(aq) + Cl2(g)

Classify & Predict CuO  Mg + O2  Ca + N2  C3H8 + O2  HCl + BaSO4  Fe + CuCl2  Cu3N + Zn  **Classify each equation on “Balancing eq” handout