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 • CO2 =6.02 E+23 CO2 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 CH4 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) C6H12O6

9. Learning Check • Ex) How many moles of H atoms are present in 0.0150 moles of NH3? 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 CO2 is: 1C + 2O = 1(12.0g) + 2(16.0g) = 44.0g Thus, 1 mole of CO2 = 44.0g

12. Learning Check • What is the molar mass of MgCl2? • 94.0g • 59.8g • 95.3g • 119.6g

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

14. Molar Mass • Any molar mass can written as a conversion factor. • From earlier: • 1 mole of CO2 = 44.0g

15. Molar Mass • This allows for the conversion between grams and moles. • Ex) 45.0g of BaCl2 = ? 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 C2H6 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 C5H10O5 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 + __Cl2  __AlCl3 • Reaction is NOT balanced! • Note: can NOT alter any subscripts! • Make a tally sheet.

28. Learning Check • Balance the following: • __FeCl2 + __Al  __AlCl3 + __Fe • __Al2(SO4)3 + KOH  Al(OH)3 + K2SO4

29. Learning Check • Balance the following: • __H3PO3  __H3PO4 + __PH3 • __C3H8 + __O2  __CO2 + __H2O

30. Learning Check • Balance the following: • __C4H8O + __O2  __CO2 + __H2O

31. Types of Reactions • Combination Reaction • 2Al(s) + 3Br2(l)  2AlBr3(s) • CaO(s) + CO2(g)  CaCO3(s)

33. Types of Reactions • Decomposition Reaction • (NH4)2Cr2O7(s)  Cr2O3(s) + 4H2O(g) + N2(g)

35. Types of Reactions • Single Replacement Reactions • Mg(s) + CuCl2(s)  MgCl2(s) + Cu(s)

37. Types of Reactions • Double Replacement Reactions • Pb(NO3)2(aq) + K2CrO4(aq)  PbCrO4(s) + 2KNO3(aq)

39. Combustion • A rapid reaction with oxygen from the air. • CH4(g) + 2O2(g)  CO2(g) + 2H2O(l) • Also occurs in the cells of animals when glucose, C6H12O6, is converted to energy.

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

42. Chemical Reactions • N2 + 3 H2 2 NH3 • 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.

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 Mass of B Moles of A Moles of B

47. Stoichiometry • If 45.1g of N2 are used, then what mass of H2 is required?

48. Stoichiometry • If 7.25g of H2 completely reacts, what mass of NH3 is produced?

49. Stoichiometry • For the reaction: • 2C2H2 + 5O2 4CO2 + 2H2O • If 6.85g of C2H2 is completely combusted, then what mass of CO2 is produced? • a. 13.7g • b. 11.6g • c. 23.2g • d. 5.80g

50. Stoichiometry • For the reaction: • 4Al + 3O2 2Al2O3 • When 0.452g of Al completely reacts, what mass of Al2O3 is produced? • a. 3.42g • b. 0.853g • c. 0.226g • d. 23.1g