1. Chapter Five Chemical Quantities and Reactions The Mole Molar Mass Chemical Changes Chemical Equations Types of Reactions Mole Relationships in Chemical Equations Mass Calculations Energy in Chemical Reactions

2. The Mole Many things have names for a quantity or group. In chemistry, a quantity of atoms, molecules, etc. is called a mole.

3. The Mole Why a “mole”?

4. The Mole A mole of anything is 6.02 E+23 particles. This is sometimes referred to as Avogadro’s Number. Written as a number: 602,000,000,000,000,000,000,000 A mole of marbles would easily fill the entire Grand Canyon with much to spare.

5. The Mole One mole of: Carbon = 6.02 E+23 carbon atoms CO 2 =6.02 E+23 CO 2 molecules NaCl = 6.02 E+23 NaCl formula units 1 mole of anything = 6.02 E+23 particles

6. Learning Check Ex) Convert 0.0242 moles of CH 4 to molecules.

7. Learning Check Ex) Convert 4.45 E+21 atoms of Zn to moles.

8. Subscripts and Moles The subscripts in a formula can be interpreted on either an atom or mole level. Ex) C 6 H 12 O 6

9. Learning Check Ex) How many moles of H atoms are present in 0.0150 moles of NH 3 ? How many H atoms?

10. Molar Mass A molar mass of an element is the atomic mass expressed in grams. The molar mass of carbon is 12.01g

11. Molar Mass The molar mass of any compound is equal to the sum of all the atomic weights for each element in the formula. Ex) The molar mass of CO 2 is: 1C + 2O = 1(12.0g) + 2(16.0g) = 44.0g Thus, 1 mole of CO 2 = 44.0g

12. Learning Check What is the molar mass of MgCl 2 ? a) 94.0g b) 59.8g c) 95.3g d) 119.6g

13. Learning Check What is the molar mass of Al(OH) 3 ? a) 78.0g b) 46.0g c) 132.0g d) 44.0g

14. Molar Mass Any molar mass can written as a conversion factor. From earlier: 1 mole of CO 2 = 44.0g

15. Molar Mass This allows for the conversion between grams and moles. Ex) 45.0g of BaCl 2 = ? moles

16. Molar Mass Ex) 1.52 x 10 -3 moles of phosphorous tribromide = ? grams

17. Moles Combining both molar mass and Avogadro’s number concepts.

18. Learning Check An 8.15 E+21 molecules of C 2 H 6 would have a mass of:

19. Learning Check A 45.3g sample of lead(II) chloride would contain how many formula units?

20. Learning Check A 6.50 x 10 -5 g sample of C 5 H 10 O 5 will contain how many Hydrogen atoms?

21. Physical Changes A physical change is one in which the state, shape, or size of the substance is altered but not its identity. Ex) Ice melting Ex) Ripping a piece of paper Ex) Boiling ethanol Ex) Pulverizing a rock

22. Chemical Changes A chemical change is one in which matter is transformed into new kinds of matter by the rearrangement of atoms. Ex) Iron rusting Ex) Burning a log Ex) Fermenting grapes Ex) Antacid neutralizing stomach acid

23. Learning Check Decide whether each is Physical or Chemical change. a) Making Kool-aid b) Baking cookies c) Cutting an aspirin in half d) Bleaching a stained shirt

24. Chemical Equations Shows the before and after for a chemical reaction using chemical formulas.

25. Chemical Equations Symbols added having various meanings.

26. Chemical Equations A Chemical Equation is always written so that the total numbers of atoms on each side of the equation are equal. To do this, coefficients are added in front of each substance. Must use lowest whole number coefficients!

27. Chemical Equations __Al + __Cl 2  __AlCl 3 Reaction is NOT balanced! Note: can NOT alter any subscripts! Make a tally sheet.

28. Learning Check Balance the following: __FeCl 2 + __Al  __AlCl 3 + __Fe __Al 2 (SO 4 ) 3 + KOH  Al(OH) 3 + K 2 SO 4

29. Learning Check Balance the following: __H 3 PO 3  __H 3 PO 4 + __PH 3 __C 3 H 8 + __O 2  __CO 2 + __H 2 O

30. Learning Check Balance the following: __C 4 H 8 O + __O 2  __CO 2 + __H 2 O

31. Types of Reactions Combination Reaction 2Al(s) + 3Br 2 (l)  2AlBr 3 (s) CaO(s) + CO 2 (g)  CaCO 3 (s)

33. Types of Reactions Decomposition Reaction (NH 4 ) 2 Cr 2 O 7 (s)  Cr 2 O 3 (s) + 4H 2 O(g) + N 2 (g)

35. Types of Reactions Single Replacement Reactions Mg(s) + CuCl 2 (s)  MgCl 2 (s) + Cu(s)

37. Types of Reactions Double Replacement Reactions Pb(NO 3 ) 2 (aq) + K 2 CrO 4 (aq)  PbCrO 4 (s) + 2KNO 3 (aq)

39. Combustion A rapid reaction with oxygen from the air. CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 O(l) Also occurs in the cells of animals when glucose, C 6 H 12 O 6, is converted to energy.

41. Chemical Reactions A reaction can be interpreted in many ways. Atoms and molecules Moles Masses

42. Chemical Reactions N 2 + 3 H 2  2 NH 3 Molecular interpretation Mole interpretation Mass interpretation

43. Law of Conservation of Mass In any chemical reaction, matter cannot be created nor destroyed. Masses of reactants = Masses of products.

44. N2N2 H2H2 NH 3 15 molecules 2.4 moles 0.014 moles

45. Stoichiometry The calculation of chemical quantities in a reaction. Relates a mass of a reactant or product to any other reactant or product.

46. Stoichiometry Mass of A Moles of AMoles of B Mass of B

47. Stoichiometry If 45.1g of N 2 are used, then what mass of H 2 is required?

48. Stoichiometry If 7.25g of H 2 completely reacts, what mass of NH 3 is produced?

49. Stoichiometry For the reaction: 2C 2 H 2 + 5O 2  4CO 2 + 2H 2 O If 6.85g of C 2 H 2 is completely combusted, then what mass of CO 2 is produced? a. 13.7g b. 11.6g c. 23.2g d. 5.80g

50. Stoichiometry For the reaction: 4Al + 3O 2  2Al 2 O 3 When 0.452g of Al completely reacts, what mass of Al 2 O 3 is produced? a. 3.42g b. 0.853g c. 0.226g d. 23.1g

51. Energy in Reactions Collision Theory In the game of pool (billiards), in order to sink a ball in the pocket what is needed? In reactions, what is needed?

52. Activation Energy The activation energy is the minimum amount of energy required to produce a reaction.

53. Exo- and Endothermic Reactions Reactions that release heat energy are said to be ________________. Reactions that absorb heat energy are said to be ________________.

54. Exo- and Endothermic Reactions

55. Exothermic Reactions Energy level of the products is lower than that of the reactants. Heat is a product and can be included in the balanced reaction. Ex) C(s) + 2H 2 (g)  CH 4 (g) + 18 kcal

56. Endothermic Reactions Energy level of the products is higher than that of the reactants. Heat is a reactant. Ex) N 2 (g) + O 2 (g) + 43.3 kcal  2NO(g)

57. Rate of a Reaction Reactions can range from instantaneous (very fast) to very slow. We can affect the rate of reaction by: Increasing the concentration of the reactants.

58. Rate of a Reaction Increasing the temperature of the reactants. This increases the fraction of molecules that have enough energy to react. Adding a catalyst. A catalyst lowers the activation energy.

59. 2H 2 O 2(aq)  2H 2 O (l) + O 2(g)