Chapter 24

1. Chapter 24 Chemical Reactions

2. In a chemical Reaction . . . Reactants Products New substances produced • Substances reacting • Any state of matter • Follow law of conservation of mass • Example: Which are the reactants? Which are the products? • NaCl Na+ + Cl- 2HgO O2 + 2Hg • NiCl2 + 2NaOHNi(OH)2 + 2NaCl

3. Law of Conservation of Mass • In the late 1700s • Antoine Lavoisier • Mass is changed; NOT created or destroyed Example: 2HgO O2 + 2Hg 10.0g = 0.7g + 9.3g Try: Zn + 2HCl  H2 + ZnCl2 15.0g + 3.2g = 6.2g + _____ 12.0g

4. Chemical Changes in Equations • Table 1 on page 740 • We use formulas and equations to shorten the writing process • It helps us see how many atoms are involved

5. Balancing Equations - Nuts and Bolts Lab Revisited 1. Build these compounds if Boltium (Bo) and Nutter (Nu) Bo2Nu3BoNu Nu How many of each compound to balance Bo2Nu3  BoNu + Nu

6. Balancing Equations - Nuts and Bolts Lab Revisited 2. Build these compounds BoNu2 Bo3 Nu How many of each compound to balance BoNu2  Bo3 + Nu

7. Balancing Equations - Nuts and Bolts Lab Revisited 3. Build these compounds Bo2Nu2 Bo3 Nu How many of each compound to balance Bo3 + Nu  Bo2Nu2

8. Balancing equations Steps Example Lithium metal treated with water, a hydrogen gas and a lithium hydroxide are produced: Li (s) + H2O  LiOH + H2 (g) Li 1 = 1 H 2 = 1 + 2 O 1 = 1 • Write chemical equation with balanced molecules (cheat sheet for poly + diatomic) • Check equation for atom balance

9. Balancing equations Steps Example Li (s) + H2O  LiOH + H2 (g) 4Li (s) + 4H2O  4LiOH + 2H2 (g) Li 4 = 4 H 8 = 4 + 4 O 4 = 4 3. Choose coefficients to balance it 4. Recheck number of atoms