1. Living By Chemistry SECOND EDITION Unit 4: TOXINS Stoichiometry, Solution Chemistry, and Acids and Bases

2. Lesson 73: What’s Your Reaction? Types of Reactions

3. ChemCatalyst Consider these reactions: CaCO 3 (aq)  CaO(aq) + CO 2 (g) CO 2 (g) + NaOH(aq)  NaHCO 3 (aq) a.How are these two reactions different? b.How would you describe, in words, what happens to the reactants in each case?

4. Key Question How do atoms rearrange to form new products?

5. You will be able to: identify patterns in chemical equations that reflect different types of reactions classify chemical equations as representing combination, decomposition, single exchange, or double exchange reactions

6. Prepare for the Activity Work in pairs.

7. Discussion Notes CombinationCO 2 (g) + NaOH(aq)  NaHCO 3 (aq) Decomposition CaCO 3 (aq)  CaO(aq) + CO 2 (g) Single exchange Cl 2 (g) + 2NaBr(s)  2NaCl(s) + Br 2 (l) Double exchange 2AgCl(s) + BaBr 2 (aq)  2AgBr(s) + BaCl 2 (aq)

8. Discussion Notes (cont.) CombinationA + B  AB Decomposition AB  A + B Single exchange A + BC  AC + B Double exchange AB + CD  AD + CB

9. Discussion Notes (cont.) Chemical reactions can be divided into categories based on how the atoms in the reactants rearrange to form the products. Combination reaction: Several reactants combine to form a single product. Combination reactions are easy to spot because there is only one compound on the product side of the equation. The general reaction can be written as A  B  AB.

10. Discussion Notes (cont.) Decomposition reaction: A compound breaks down as a result of the chemical change. Decomposition reactions are easy to spot because there is only one reactant. The general reaction can be written as AB  A  B.

11. Discussion Notes (cont.) Single exchange reaction: A compound breaks apart, and one part combines with the other reactant—either an atom or a group of atoms such as OH -, CO 3 2-, or NO 3. Typically, one of the reactants is an element. The general reaction can be written as A  BC  AC  B, where A displaces B.

12. Discussion Notes (cont.) Double exchange reaction: Both reactants break apart. Their parts then recombine into two new products. Thus, the two reactants exchange parts. The general reaction can be written as AB + CD  AD + CB, where B and D exchange with each other (or A and C exchange with each other).

13. Discussion Notes (cont.) Toxins can react in any of these ways in the body, depending on the toxin and the circumstances.

14. Wrap Up How do atoms rearrange to form new products? Chemical reactions can be sorted into categories based on how the atoms in the reactants rearrange to form the products. Four general types of chemical reactions are combination reactions, decomposition reactions, single exchange reactions, and double exchange reactions.

15. Check-In Examine this chemical equation, which describes a double exchange between silver nitrate and sodium chloride. Predict the products. Make sure the equation is balanced. AgNO 3 (aq)  NaCl(aq)  Ag____(s) + Na_____(aq)