Chemical Equations & Reactions CHAPTER 8 Chemical Equations & Reactions

Chemical Equations Represented w/ symbols & formulas Identifies reactants & products Identifies amounts of each

What Do They Tell Us?

Evidence of a Chemical Reaction Section 1 Describing Chemical Reactions Chapter 8 Evidence of a Chemical Reaction solution color changes solution bubbles copper is used up

Evidence of a Chemical Reaction Produces heat and/or light Produces gas Forms a precipitate (a solid appears) Color change Temperature change

Balancing Chemical Reactions Why do it? We need to know exactly how much of everything there is. What do you do? Count Make sure the exact same number of atoms exists on both sides of the eqn.

Reading a Chemical Equation Chapter 8 Visual Concepts Reading a Chemical Equation

Rules of Balancing Write each individual formula (Criss-Cross Applesauce) Take inventory Use coefficients to balance. Check your work.

H2O two hydrogens / 1 oxygen Coefficients #’s that go in front They multiply Example H2O two hydrogens / 1 oxygen 2 H2O 4 hydrogens/ 2 oxygens 5 H2O 10 hydrogens / 5 oxygens

Sample Problem A Na + Cl2  NaCl 1

Sample Problem A Na + Cl2  NaCl 1 2

Sample Problem A Na + Cl2  NaCl 1 2 1

Sample Problem A Na + Cl2  NaCl 1 2 1 1 Cl are not equal. 1 2 1 1 Cl are not equal. Use a coefficient!

Sample Problem A Na + Cl2  2 NaCl Now count again!

Sample Problem A Na + Cl2  2 NaCl 1

Sample Problem A Na + Cl2  2 NaCl 1 2

Sample Problem A Na + Cl2  2 NaCl 1 2 2

Sample Problem A Na + Cl2  2 NaCl 1 2 2 2 1 2 2 2 Now the Na atoms aren’t equal! Use another coefficient.

Sample Problem A 2 Na + Cl2  2 NaCl

Sample Problem A 2 Na + Cl2  2 NaCl 2

Sample Problem A 2 Na + Cl2  2 NaCl 2 2

Now everything is EQUAL! Sample Problem A 2 Na + Cl2  2 NaCl 2 2 2 2 Now everything is EQUAL! 2 Na + Cl2  2 NaCl

Ca3(PO4)2 + Mg(OH)2 → Ca(OH)2 + Mg3(PO4)2 Sample Problem B Ca3(PO4)2 + Mg(OH)2 → Ca(OH)2 + Mg3(PO4)2 COUNT!

Ca3(PO4)2 + Mg(OH)2 → 3 Ca(OH)2 + Mg3(PO4)2 Sample Problem B Ca3(PO4)2 + Mg(OH)2 → 3 Ca(OH)2 + Mg3(PO4)2

Ca3(PO4)2 + 3 Mg(OH)2 → 3 Ca(OH)2 + Mg3(PO4)2 Sample Problem B Ca3(PO4)2 + 3 Mg(OH)2 → 3 Ca(OH)2 + Mg3(PO4)2

Types of Chemical Reactions

Chapter 8 Visual Concepts Synthesis Reactions

Synthesis Reactions Smaller compounds make one bigger one A + B  AB Example: Na + Cl  NaCl

Decomposition Reaction Chapter 8 Visual Concepts Decomposition Reaction

Decomposition Larger compounds break down to smaller ones Opposite of synthesis reaction AB  A + B Example: 2 KClO3  2 KCl + 3 O2

Single Displacement Reaction Chapter 8 Visual Concepts Single Displacement Reaction

Single Replacement Reaction One atom changes places with another atom A + BC  AC + B Example: Zn + 2 HCl  H2 + ZnCl2

Double-Displacement Reaction Chapter 8 Visual Concepts Double-Displacement Reaction

Double Replacement Reaction Two atoms trade places AB + CD  AD + CB Example: 2 KI + Pb(NO3)2  2 KNO3 + PbI2

Precipitation Reaction Chapter 8 Visual Concepts Precipitation Reaction

Chapter 8 Visual Concepts Combustion Reaction

Combustion Reaction Anything reacting with O2 X + O2  CO2 + H2O

1. What type of chemical reaction involves the exchange of the ions of two compounds in an aqueous solution to form two new compounds? A. synthesis reaction B. decomposition reaction C. single-displacement reaction D. double-displacement reaction

1. What type of chemical reaction involves the exchange of the ions of two compounds in an aqueous solution to form two new compounds? A. synthesis reaction B. decomposition reaction C. single-displacement reaction D. double-displacement reaction

2. Which of these sentences correctly states the law of conservation of mass? F. In a chemical reaction, the mass of the products cannot exceed the mass of the reactants. G. In a chemical reaction, the mass of the products is always equal to the mass of the reactants. H. In a chemical reaction, the mass of the products is always less than the mass of the reactants. I. In a chemical reaction, the mass of the products is always greater than the mass of the reactants.

2. Which of these sentences correctly states the law of conservation of mass? F. In a chemical reaction, the mass of the products cannot exceed the mass of the reactants. G. In a chemical reaction, the mass of the products is always equal to the mass of the reactants. H. In a chemical reaction, the mass of the products is always less than the mass of the reactants. I. In a chemical reaction, the mass of the products is always greater than the mass of the reactants.

3. Of these reaction types, which has only one reactant? A. decomposition B. displacement C. oxidation D. synthesis

3. Of these reaction types, which has only one reactant? A. decomposition B. displacement C. oxidation D. synthesis