Chapter 11 Matter and Change 11.1 Describing Chemical Reactions 11.2 Types of Chemical Reactions

1. Chapter 11 Matter and Change 11.1 Describing Chemical Reactions 11.2 Types of Chemical Reactions 11.3 Reactions in Aqueous Solution

2. Introduction to Chemical Equations Do Now: Work with your table mates to come up with a list of 10 chemical reactions that you have seen or heard of.

3. Introduction to Chemical Equations • How do you know if a chemical reaction is taking place? • https://www.youtube.com/watch?v=FofPjj7v414

4. Introduction to Chemical Equations Signs of a Chemical Reaction • Transfer of energy • Change in color • Production of a gas • Formation of a precipitate

5. Introduction to Chemical Equations • How do you describe what is happening in a chemical reaction?

6. Introduction to Chemical Equations Word Equations Reactants → Products • Reactants are on the left, products on the right. • An arrow separates them. • You read the arrow as yields, gives, or reacts to produce.

7. Introduction to Chemical Equations Word Equations Iron + oxygen → iron(III) oxide • Rusting of Iron • You could say, “Iron reacts with oxygen to produce iron(III) oxide (rust).”

8. Introduction to Chemical Equations Skeleton Equations Equations that show just the formulas of the reactants and products. Fe + O2→ Fe2O3 • The first step in writing a complete chemical equation is to write the skeleton equation.

9. Δ Pt heat InterpretData

10. Introduction to Chemical Equations Chemical Equations Indicate the physical states of substances by putting a symbol after each formula. • (s) for solid • (l) for liquid, • (g) for gas, • (aq) for a substance in an aqueous solution (a substance dissolved in water). Fe(s) + O2(g) → Fe2O3(s)

11. Introduction to Chemical Equations MnO2 H2O2(aq) H2O(l) + O2(g) Chemical Equations Catalyst: substance that speeds up the reaction but is not used up in the reaction. • A catalyst is neither a reactant nor a product, so its formula is written above the arrow in a chemical equation.

12. SampleProblem 11.1 Write a Skeleton Equation Hydrochloric acid reacts with solid sodium hydrogen carbonate. The products formed are aqueous sodium chloride, water, and carbon dioxide gas. Write a skeleton equation for this chemical reaction.

13. SampleProblem 11.1 Write a Skeleton Equation Hydrochloric acid reacts with solid sodium hydrogen carbonate. The products formed are aqueous sodium chloride, water, and carbon dioxide gas. Write a skeleton equation for this chemical reaction. NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)

14. Balancing Chemical Equations Law of Conservation of Mass • During any chemical reaction, the mass of the products always equals the mass of the reactants. • Atoms are neither created nor destroyed in ordinary chemical reactions. • The same number of atoms of each element must be present on both sides of the equation.

15. Balancing Chemical Equations What does that mean for you? • The same number of atoms of each element must be present on both sides of the equation. • Add coefficients to balance the reactants and products. Do not add subscripts!

16. Balancing Chemical Equations Coefficients— small whole numbers that are placed in front of the formulas in an equation in order to balance it.

17. Balancing Chemical Equations Balanced equation: each side of the equation has the same number of atoms of each element and mass is conserved.

18. Balancing Chemical Equations To write a balanced chemical equation 1. Write the skeleton equation. 2. Use coefficients to balance the equation so that it obeys the law of conservation of mass.

19. Balancing Chemical Equations C(s)Carbon O2(g)Oxygen + CO2(g)Carbon dioxide Reactants1 carbon atom, 2 oxygen atoms Product1 carbon atom, 2 oxygen atoms Carbon burns in the presence of oxygen to produce carbon dioxide. • This equation is balanced. • You do not need to change the coefficients. • They are all understood to be 1.

20. Balancing Chemical Equations When hydrogen and oxygen are mixed, the product is water. • The formulas for all the reactants and the product are correct, but this equation is not balanced. • As written, the equation does not obey the law of conservation of mass.

21. Balancing Chemical Equations When hydrogen and oxygen are mixed, the product is water. • If you put the coefficient 2 in front of H2O, oxygen will be balanced. • Now twice as many hydrogen atoms are in the product as are in the reactants.

22. Balancing Chemical Equations When hydrogen and oxygen are mixed, the product is water. • To correct this equation, put the coefficient 2 in front of H2. • The equation is now balanced.

23. CHEMISTRY&YOU The reaction between oxygen and hydrogen in fuel cells produces the energy to power a car. What are the products of the reaction in a fuel cell that make the fuel-cell car a zero-emission car?

24. CHEMISTRY&YOU The reaction between oxygen and hydrogen in fuel cells produces the energy to power a car. What are the products of the reaction in a fuel cell that make the fuel-cell car a zero-emission car? Water is the product of the reaction between oxygen and hydrogen in a fuel cell. Water is not a pollutant, and so fuel-cell cars are considered “zero-emission” cars.

25. InterpretData

26. SampleProblem 11.2 Balancing a Chemical Equation Students suspended copper wire in an aqueous solution of silver nitrate. They noticed a deposit of silver crystals on the copper wire when the copper reacted with the silver nitrate. They recorded the equation for this reaction but didn’t balance it. Balance their equation: AgNO3(aq) + Cu(s) → Cu(NO3)2(aq) + Ag(s)

27. 2 Solve Apply concepts to this situation. Remember that a coefficient must always go in front of a compound’s formula, not in the middle of it. SampleProblem 11.2 Balance the nitrate ion. • Put a coefficient 2 in front of AgNO3(aq). 2AgNO3(aq) + Cu(s) → Cu(NO3)2(aq) + Ag(s)

28. 2 Solve Apply concepts to this situation. SampleProblem 11.2 Balance the silver. • Put a coefficient 2 in front of Ag(s). 2AgNO3(aq) + Cu(s) → Cu(NO3)2(aq) + 2Ag(s)

29. SampleProblem 11.3 Balancing a Chemical Equation Aluminum is a good choice for outdoor furniture because it reacts with oxygen in the air to form a thin protective coat of aluminum oxide. Balance the equation for this reaction. Al(s) + O2(s) → Al2O3(s)

30. Analyze Identify the relevant concepts. 1 SampleProblem 11.3 Apply the rules for balancing equations. • Notice the odd number of oxygen atoms in the product. Al(s) + O2(s) → Al2O3(s)

31. 2 Solve Apply concepts to this situation. SampleProblem 11.3 First balance the aluminum by placing the coefficient 2 in front of Al(s). 2Al(s) + O2(s) → Al2O3(s)

32. 2 Solve Apply concepts to this situation. Any whole-number coefficient placed in front of O2 will always give an even number of oxygen atoms on the left. SampleProblem 11.3 Multiply the formula with the odd number of oxygen atoms (on the right) by 2 to get an even number of oxygen atoms on the right. 2Al(s) + O2(s) → 2Al2O3(s)

33. 2 Solve Apply concepts to this situation. SampleProblem 11.3 Balance the oxygens on the left by placing a 3 in front of O2. 2Al(s) + 3O2(s) → 2Al2O3(s)

34. 2 Solve Apply concepts to this situation. SampleProblem 11.3 Then rebalance the aluminum by changing the coefficient of Al(s) from 2 to 4. 4Al(s) + 3O2(s) → 2Al2O3(s)

35. https://www.youtube.com/watch?v=2S6e11NBwiw

36. Balance the following equation. C3H8(g) + O2(g) → CO2(g) + H2O(l)

37. Balance the following equation. C3H8(g) + O2(g) → CO2(g) + H2O(l) C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)

38. END OF 11.1