1. 1 Session 3.2: Chemical Reactions Tom Hsu, PhD. Manos Chaniotakis, PhD. Marina Dang, PhD. Copyright © 2012 Chaniotakas and Hsu

2. Essential Questions How do we describe a chemical reaction? How do we quantify a reaction?

3. Objectives Safely and correctly run three chemical reactions. Model each chemical change. Use coefficients to balance chemical equations. Where does the blue “cloud” come from?

4. TEKS 8 (A) define and use the concept of a mole; 8 (B) use the mole concept to calculate the number of atoms, ions, or molecules in a sample of material; 8 (C) calculate percent composition and empirical and molecular formulas; 8 (D) use the law of conservation of mass to write and balance chemical equations; and 8 (E) perform stoichiometric calculations, including determination of mass relationships between reactants and products, calculation of limiting reagents, and percent yield.

5. Assessment Use 3D models to illustrate and balance the following chemical equation: How many moles of NaOH does it take to produce 2.7 g of Cu(OH) 2 ? __ NaOH + __ CuCl 2  __ NaCl + __Cu(OH) 2

6. Review Chemicals are mixed, but no chemical bonds are broken. No new substances are formed. Physical changeChemical change Chemicals bonds are broken and formed. One or more new substances are produced. Water + food dye Bleach + food dye

7. Chemical equations We use chemical equations to describe chemical reactions.

8. Chemical equations ReactantsProducts The numbers in front of the chemical formulas are called coefficients. The general form of a chemical equation is: Reactant 1 + Reactant 2 Product 1 + Product 2

9. Safety rules Do not consume food or drinks in the lab. Wear appropriate protective gear. Report all spills and accidents. Work methodically, and ask questions if necessary. Understand the hazards of the chemicals you are using. Protect yourself against different types of hazards.

10. Chemical equations We will now perform, model, and analyze 3 different types of reactions: 1.Acid–base reaction 2.Redox (oxidation–reduction) reaction 3.Precipitate reaction Materials 5 mL of 1.0 M NaOH 5 mL of 1.0 M HCl Phenolphthalein 1 small piece of Mg 1 mL of 1.0 M CuSO 4 3 test tubes on a rack Gloves Goggles

11. 1.Add ~2 mL of 1.0 M HCl to a test tube. 2.Add 2 drops of phenolphthalein. 3.Add drops of 1.0 M NaOH until a pink color persists. 4.Write down observations, then safely set chemicals aside. An acid–base reaction

12. 1.Build models of the reactants HCl and NaOH. 2.Rearrange the atoms from the reactants to build the products NaCl and H 2 O. An acid–base reaction

13. Have students write how many models of HCl and NaOH they started with. Number of HCl models you built Number of NaOH models you built Number of NaCl models you obtained Number of H 2 O models you obtained An acid–base reaction Have students write how many models of NaCl and H 2 O they ended up with.

14. Have students write how many models of HCl and NaOH they started with. Number of HCl models you built Number of NaOH models you built Number of NaCl models you obtained Number of H 2 O models you obtained An acid–base reaction Have students write how many models of NaCl and H 2 O they ended up with. 1111

15. 1111 2 2 Count the number of each type of atom on each side of the reaction arrow. An acid–base reaction

16. 1111 2 2 1 1 1 1 1 1 The equation is balanced.

17. An acid–base reaction HCl + NaOH NaCl + H 2 O How many moles of NaCl is produced if the reaction results in 3.0 mol of H 2 O? Chemical equation: Question:

18. An acid–base reaction HCl + NaOHNaCl + H 2 O How many moles of NaCl is produced if the reaction results in 3.0 mol of H 2 O? Chemical equation: Question: Relationship: What is the mole ratio between NaCl and H 2 O?

19. An acid–base reaction HCl + NaOH NaCl + H 2 O How many moles of NaCl is produced if the reaction results in 3.0 mol of H 2 O? Chemical equation: Question: Relationship: What is the mole ratio between NaCl and H 2 O? 1 mol NaCl 1 mol H 2 O

20. An acid–base reaction HCl + NaOHNaCl + H 2 O How many moles of NaCl is produced if the reaction results in 3.0 mol of H 2 O? Chemical equation: Question: Relationship: What is the mole ratio between NaCl and H 2 O? 1 mol NaCl 1 mol H 2 O Answer: 3.0 mol H 2 O x = 3.0 mol NaCl

21. An acid–base reaction HCl + NaOH NaCl + H 2 O How many moles of NaOH does it take to produce 1.8 mol of H 2 O? Chemical equation: Question:

22. An acid–base reaction HCl + NaOH NaCl + H 2 O Chemical equation: Question: Relationship: What is the mole ratio between NaOH and H 2 O? 1 mol NaOH 1 mol H 2 O How many moles of NaOH does it take to produce 1.8 mol of H 2 O?

23. An acid–base reaction HCl + NaOHNaCl + H 2 O Chemical equation: Question: Relationship: 1 mol NaOH 1 mol H 2 O Answer: 1.8 mol H 2 O x = 1.8 mol NaOH How many moles of NaOH does it take to produce 1.8 mol of H 2 O? What is the mole ratio between NaOH and H 2 O?

24. 1.Add ~3 mL of 1.0 M HCl to a test tube. 2.Carefully add a piece of magnesium. 3.Record your observations. 4.Safely set the chemicals aside. A redox reaction

25. 1.Build models of the reactants. You may use a 2-hole yellow ball for magnesium. 2.Rearrange the atoms from the reactants to build the products MgCl 2 and H 2. A redox reaction

26. 1.Build models of the reactants. You may use a 2-hole yellow ball for magnesium. 2.Rearrange the atoms from the reactants to build the products MgCl 2 and H 2. A redox reaction If you are struggling, try building the products first. Use the atoms from the products to make the reactants. What do you notice?

27. Have students write how many models of each chemical they built / obtained. Number of Mg models you got Number of HCl models you got Number of MgCl 2 models you used Number of H 2 models you used A redox reaction

28. Have students write how many models of each chemical they built / obtained. Number of Mg models you got Number of HCl models you got Number of MgCl 2 models you used Number of H 2 models you used A redox reaction 1211

29. Count the number of each type of atom on each side of the reaction arrow. A redox reaction 1211

30. 1 1 2 2 2 2 The equation is balanced. A redox reaction 1211

31. Mg + 2HClMgCl 2 + H 2 Chemical equation: Question: How many moles of Mg does it take to produce 0.45 mol of H 2 ?

32. A redox reaction Mg + 2HClMgCl 2 + H 2 Chemical equation: Relationship: What is the mole ratio between Mg and H 2 ? Question: How many moles of Mg does it take to produce 0.45 mol of H 2 ? 1 mol Mg 1 mol H 2

33. A redox reaction Mg + 2HClMgCl 2 + H 2 Chemical equation: Relationship: What is the mole ratio between Mg and H 2 ? Question: How many moles of Mg does it take to produce 0.45 mol of H 2 ? 1 mol Mg 1 mol H 2 Answer: 4.5 mol H 2 x = 4.5 mol Mg

34. A redox reaction Mg + 2HClMgCl 2 + H 2 Chemical equation: Question: How much MgCl 2 is produced (in grams) from 1.7 mol of HCl?

35. A redox reaction Mg + 2HClMgCl 2 + H 2 Chemical equation: Relationship: What is the mole ratio between MgCl 2 and HCl? 1 mol MgCl 2 2 mol HCl Question: How much MgCl 2 is produced (in grams) from 1.7 mol of HCl?

36. A redox reaction Mg + 2HClMgCl 2 + H 2 Chemical equation: Relationship: What is the mole ratio between MgCl 2 and HCl? 1 mol MgCl 2 2 mol HCl Question: How much MgCl 2 is produced (in grams) from 1.7 mol of HCl? Answer: 1.7 mol HCl x = 0.85 mol MgCl 2

37. 1.Add ~3 mL of 1.0 M NaOH to a test tube. 2.Carefully add 3 to 5 drops of 1.0 M CuSO 4. 3.Record your observations. 4.Safely set the chemicals aside. A precipitate reaction

38. 1.Build models of the reactants. You may model Cu with the orange ball, but remember to only use 2 bonding sites. (Hint: There should be two S=O bonds.) 2.Rearrange the atoms from the reactants to build the products. A precipitate reaction

39. If you are struggling, try building the products first. Use the atoms from the products to make the reactants. A precipitate reaction 1.Build models of the reactants. You may model Cu with the orange ball, but remember to only use 2 bonding sites. (Hint: There should be two S=O bonds.) 2.Rearrange the atoms from the reactants to build the products.

40. Have students write how many models of each chemical they built / obtained. Number of NaOH models you got Number of CuSO 4 models you got Number of Na 2 SO 4 models you used Number of Cu(OH) 2 models you used A precipitate reaction

41. Have students write how many models of each chemical they built / obtained. Number of NaOH models you got Number of CuSO 4 models you got Number of Na 2 SO 4 models you used Number of Cu(OH) 2 models you used A precipitate reaction 1121

42. Count the number of each type of atom on each side of the reaction arrow. A precipitate reaction 1121

43. The equation is balanced. A precipitate reaction 2 2 6 6 2 2 1 1 1 1 1121

44. 2NaOH + CuSO 4 Na 2 SO 4 + Cu(OH) 2 Chemical equation: Question: How many moles of NaOH does it take to produce 1.4 g of Cu(OH) 2 ? A precipitate reaction

45. Chemical equation: Relationship: What is the mole ratio between NaOH and Cu(OH) 2 ? 2 mol NaOH 1 mol Cu(OH) 2 A precipitate reaction Question: How many moles of NaOH does it take to produce 1.4 g of Cu(OH) 2 ? 2NaOH + CuSO 4 Na 2 SO 4 + Cu(OH) 2

46. 2 mol NaOH 1 mol Cu(OH) 2 Chemical equation: Relationship: Answer: 1.4 mol Cu(OH) 2 x = 2.8 mol NaOH A precipitate reaction 2NaOH + CuSO 4 Na 2 SO 4 + Cu(OH) 2 Question: How many moles of NaOH does it take to produce 1.4 g of Cu(OH) 2 ? What is the mole ratio between NaOH and Cu(OH) 2 ?

47. Assessment Use 3D models to illustrate and balance the following chemical equation: How many moles of NaOH does it take to produce 2.7 g of Cu(OH) 2 ? __ NaOH + __ CuCl 2  __ NaCl + __Cu(OH) 2

48. Assessment Use 3D models to illustrate and balance the following chemical equation: __ NaOH + __ CuCl 2  __ NaCl + __Cu(OH) 2

49. Assessment Use 3D models to illustrate and balance the following chemical equation: __ NaOH + __ CuCl 2  __ NaCl + __Cu(OH) 2 2112

50. How many moles of NaOH does it take to produce 2.7 g of Cu(OH) 2 ? Assessment

51. How many moles of NaOH does it take to produce 2.7 g of Cu(OH) 2 ? Assessment Relationship: What is the mole ratio between NaOH and Cu(OH) 2 ? 2 mol NaOH 1 mol Cu(OH) 2

52. How many moles of NaOH does it take to produce 2.7 g of Cu(OH) 2 ? Assessment Relationship: What is the mole ratio between NaOH and Cu(OH) 2 ? 2 mol NaOH 1 mol Cu(OH) 2 Answer: 2 mol NaOH 1 mol Cu(OH) 2 2.7 mol Cu(OH) 2 x = 5.4 mol NaOH

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