Chapter 10

1. Chemical Reactions Chapter 10

2. Homework for Chap 10 Read p 273 – 286; 288 - 293 Applying the Concepts # 1 – 37, 39 – 42, 44 – 47, 49 - 53

3. molecular empirical H2O Chemical Formulas Empirical formula shows the simplest whole-number ratio of the atoms in a substance Molecular formula shows the actual number of atoms of each element in the smallest unit of a substance H2O CH2O C6H12O6 O3 O N2H4 NH2

4. Fig. 10.2 Several ways to express common molecules

5. 3 ways of representing the reaction of H2 with O2 to form H2O reactants products Chemical reaction≡process in which one or more substances is changed into one or more new substances Chemical equation ≡ use of chemical symbols to show what happens during a chemical reaction

6. Fig. 10.4 The Combustion of Charcoal “Carbon reacts with oxygen to yield carbon dioxide” C + O2→ CO2

7. Fig. 10.5 The meaning of subscripts and coefficients

8. Fig. 10.6 Illustration of the Law of Conservation of Mass

9. Fig. 10.8 Hydrocarbons and Carbohydrates C12H22O11 C8H18 C3H8

10. Types of Chemical Reactions • Oxidation-Reduction (Redox) • Combination • Decomposition • Replacement • Ion Exchange

11. 2 Mg (s) + O2 (g) 2 MgO (s) Oxidation-Reduction Reactions (electron transfer reactions) Oxidation – an atom loses electrons Reduction – an atom gains electrons O2 is the oxidizing agent (takes electrons and is reduced) Mg is the reducing agent (supplies electrons and is oxidized) Mg2+O2-

12. Fig. 10.9 Example of an oxidizing agent (“chlorine”) Others: 1) Bleach 2) Hydrogen peroxide 3) Oxygen 4) Ultraviolet light

13. Types of Chemical Reactions • Oxidation-Reduction (Redox) • Combination • Decomposition • Replacement • Ion Exchange

14. 4 Fe (s) + 3 O2 (g) 2 Fe2O3 (s) Fig 10.10 Iron combines with oxygen to form rust (iron oxide)

15. Hydrogen combines with oxygen to form water (dihydrogen monoxide)

16. Types of Chemical Reactions • Oxidation-Reduction (Redox) • Combination • Decomposition • Replacement • Ion Exchange

17. heat 2 HgO (s)→ 2 Hg (l) + O2(g) Fig. 10.11 Decomposition of Mercury Oxide

18. Decomposition of Hydrogen Peroxide 2 H2O2(l)→ 2 H2O (l) + O2(g) (Demo)

19. Types of Chemical Reactions • Oxidation-Reduction (Redox) • Combination • Decomposition • Replacement • Ion Exchange

20. Fig. 10.13 Replacement reaction between aluminum metal and the blue copper chloride solution 2 Al (s) 3 CuCl2(aq)→ 2 AlCl3(aq) + 3 Cu (s) Cu Al AlCl3 CuCl2

21. Replacement reactions take place when • a more active metal gives up electrons • to a less active metal. • How do we know if a replacement reaction • will take place or not occur? • Refer to the activity series for common metals • Fig 10.12, p 264

22. Fig. 10.12 The activity series for common metals

23. Fig. 10.12 The activity series for common metals Zn + 2HCl ZnCl2 + H2 ↑ 2 Na + 2H2O 2NaOH + H2 ↑ Cu + HCl no reaction