Chemical Reactions and Equations in Chemistry

1. Chapter 10 Chemical Reactions

2. 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)

3. 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.”

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

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

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

7. 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)

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

9. 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**

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

11. 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.

12. ** Balance…

13. 10.2 Classifying Chemical Reactions 1. SYNTHESIS reaction- two or more substances react to form a single product. A + B  AB Na + Cl2 __________

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

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

17. 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

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

20. 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 dinitrogenpentoxide gas. • Ethane gas (C2H6) burns in air to produce carbon dioxide gas and water vapor.

21. 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)

23. Decomposition of sugar

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

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

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

27. Classify the reaction • C6H14 + O2 • Mg + N2 • H2O2  • Ag + S  • Zn + O2  • C12H22O11 

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

30. Activity Series: -------------over there

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

33. Copper plating

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

35. 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)

36. 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

37. Double replacement rxn

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

39. 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

40. 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)

41. Classify each rxn • CH4 + O2  H2O + CO2 • 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) • Single-replacement

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