CHEMICAL BONDS CHAP 9

2 For Science Fair Judges Write a 1 – 2 page word-processed report evaluating 2 projects. If you are not a judge, you may submit this assignment for 15 extra- credit points or as a lab make-up.

3 Composition of Ionic Compounds Common names: “salt” → sodium chloride “lye” → sodium hydroxide “rust” → iron oxide “baking soda” → sodium bicarbonate “chalk” → calcium carbonate

Fig Three substances containing sodium and some form of the carbonate ion

5 Names for Ionic Compounds containing only two different elements Metal (positive) ion is written and spoken first Negative element is written/spoken second Subscripts used to produce an electrically neutral compound e.g. NaCl, CaO, KI, Fe 2 O 3, CaC 2

Fig 11.6 NaCl dissolving in water

Box Fig. 9.1 Conductivity tester for determining if a solution contains ions Fact: Dissolving an ionic compound in water results in ions being pulled apart from the crystal lattice to form free ions +−

Chapter 10 Chemical Reactions

9 Homework for Chap 10 Read p 253 – 257; Applying the Concepts # 1 – 17

10 A molecular formula shows the actual number of atoms of each element in the smallest unit of a substance An empirical formula shows the simplest whole-number ratio of the atoms in a substance H2OH2O H2OH2O molecularempirical C 6 H 12 O 6 CH 2 O O3O3 O N2H4N2H4 NH 2 Chemical Formulas

Fig Several ways to express common molecules

3 ways of representing the reaction of H 2 with O 2 to form H 2 O A process in which one or more substances is changed into one or more new substances is a chemical reaction A chemical equation uses chemical symbols to show what happens during a chemical reaction reactantsproducts

Fig The Combustion of Charcoal C + O 2 → CO 2 “Carbon reacts with oxygen to yield carbon dioxide”

Fig The meaning of subscripts and coefficients

Fig Illustration of the Law of Conservation of Mass

Fig Hydrocarbons and Carbohydrates C 8 H 18 C3H8C3H8 C 12 H 22 O 11

17 Types of Chemical Reactions 1) 1)Oxidation-Reduction (Redox) 2) 2) Combination 3) 3) Decomposition 4) 4) Replacement 5) 5) Ion Exchange

18 Oxidation-Reduction Reactions (electron transfer reactions) 2Mg (s) + O 2 (g) 2MgO (s) Mg is the reducing agent (supplies electrons) O 2 is the oxidizing agent (takes electrons) Oxidation – an atom loses electrons Reduction – an atom gains electrons

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

20 Types of Chemical Reactions 1) 1)Oxidation-Reduction (Redox) 2) 2) Combination 3) 3) Decomposition 4) 4) Replacement 5) 5) Ion Exchange

Fig Iron combines with oxygen to form rust (iron oxide) 4 Fe (s) + 3 O 2 (g) 2 Fe 2 O 3 (s)

22 Types of Chemical Reactions 1) 1)Oxidation-Reduction (Redox) 2) 2) Combination 3) 3) Decomposition 4) 4) Replacement 5) 5) Ion Exchange

Fig Decomposition of Mercury Oxide 2 HgO (s) → 2 Hg (l) + O 2 (g) heat