1 Chapter Objectives Balance chemical equations Avogadro’s number, Mole, and Molar Mass Mass-mole conversion Solve mole-to-mole and mass-to-mass using balanced equation Reduction/oxidation reaction

22 Experiencing Chemical Change Chemical Reactions: happening both around you and in you all the time! +  some are very simple, others are complex involving changes in the structures of the molecules  many times we can experience the effects of those changes Chemical reactions you experience? Combustion of gasoline/natural gas Seasonal color change of leaves Bleaching of laundry

33 Chemical Reactions Chemical changes: New matter forms Rearrangement and exchange of atoms to produce new molecules Elements are not transmuted A reaction resemble life cyclesA reaction resemble life cycles (at 1:45) Reactants  Products

44 Chemical Equations: Conservation of Mass Matter cannot be created or destroyed Total mass cannot change Total mass of the reactants will be the same as the total mass of the products: Mass Reactant = Mass Product All the atoms present at the beginning are still present at the end: #Atom X (Reactant) = #Atom X (Product) if all the atoms are still there, then the mass will not change

55 Components in Chemical Equations: 2Mg(s) + O 2 (g)  2MgO(s) Shorthand way of describing a reaction Provides information about the reaction Formulas of Reactants (Left) and Products (Right) States of Reactants and Products in “( )”. (solid/liquid/gas) Relative #Reactant and #Product molecules (Coefficients)

6 6 Symbols Used in Equations Indicating the state after chemical (g) = gas; (l) = liquid; (s) = solid (aq) = aqueous = dissolved in water energy symbols used above the arrow for decomposition reactions  = heat h = light shock = mechanical elec = electrical

77 Combustion of Methane: Balanced! To obey the Law of Conservation of Mass, the equation must be balanced CH 4 (g) + 2 O 2 (g)  CO 2 (g) + 2 H 2 O(g) H H C H H + O O C + OO OO + O HH O HH + 1 C + 4 H + 4 O

88 Balance Table For a balanced equation, there are equal numbers of atoms of each element on the Reactant and Product sides to obtain the number of atoms of an element, multiply the subscript by the coefficient 1  C  1 4  H  4 4  O  CH 4 (g) + 2 O 2 (g)  CO 2 (g) + 2 H 2 O(g)

99 How to Write & Balance Chemical Equation 1.Skeletal equation 2.Balance table: Polyatomic ions as one “Group”. 3. Pick an element to balance: Pick Element/Group w/ highest #Atoms 4.Find the Least Common Multiple 5.Multiply each count by a factor to equal the LCM. 6.Recount and Repeat until Balanced. __CH 4 O(g) + __O 2 (g)  __CO 2 (g) + __H 2 O(g)

10 Example Solid aluminum react with aqueous sulfuric acid to form aqueous aluminum sulfate and hydrogen gas 1.Write a skeletal equation. 2.Count #Atom or #Groups 3.Setup balancing table and balance. Don’t start with elements in more than one formula 4.Find the Least Common Multiple of the number of atoms on each side.

11 Example Fe(CN) 3 (s) + H 2 SO 4 (aq)  Fe 2 (SO 4 ) 3 (aq) + HCN(aq) ____ and ____ are groups

12 Example: Balance equation C 8 H 18 + O 2  CO 2 + H 2 O

13 Practice: Balancing Equations C 12 H 22 O 11 + O 2  CO 2 + H 2 O (NH 4 ) 3 PO 4 + Ca(NO 2 ) 2  Ca 3 (PO 4 ) 2 + NH 4 NO 2

14 Why is Knowledge of Composition Important? everything in nature is either chemically or physically combined with other substances to know the amount of a material in a sample, you need to know what fraction of the sample it is Some Applications: the amount of sodium in sodium chloride for diet the amount of iron in iron ore for steel production the amount of hydrogen in water for hydrogen fuel the amount of chlorine in Freon to estimate ozone depletion

15 Counting Pennies by Weight What if a person doesn’t have bills but pounds of pennies when he wants to buy a $10 pizza? Seinfeld : Kramer’s attempt to buy calzone with pennies Assuming each penny weighs exactly the same (2.500 g), we can count pennies by weight the total weight of pennies…

16 Counting Pennies by Weight Kramer brought 2,500. g (ca. 5.5 lbs) of new pennies to the Italian restaurant. Do you think he can buy three calzones ($10.0 total)? Each new penny weighs g.

17 Counting Coins by Weight What if Kramer brought different coins? Would the mass of single dime be g? Would there be $10.00 in 2,500. g dimes? How would this affect the weight-dollar conversion factors?

18 Mass of atoms Atoms of the same element have on average the same mass. amu Mass of atom in amu (atomic mass unit): 1 amu = × kg Mass of a C-12 atom = 12 (exact) amu Mass of a gold atom on average = amu Do I have to memorize these numbers?!

19 Counting atoms by mass For example, the ratio between the masses of a carbon atom and a gold atom is approximately 1 : 16.4 Similar to how we count the number of pennies, we can count the number of atoms using their mass The number of atoms in a sample often is an astronomical number, so we use a big unit to account for the number of atoms. Just like 1 dozen = 12 items

20 Mole “Chemical Dozen” – the Mole The number of particles in 1 mole: Avogadro’s Number = _______________ units 1 mole of any atomic element has x atoms 1 mole of oxygen gas has x O 2 molecules 1 mole of NaCl solid has x Na + ions and x Cl - ions

21 Avogadro’s Number as Conversion Factor Given number of Moles  number of Units Given number of Units  Mole #Units Mole # 

22 Information Given:0.041 moles of Ag atoms Find:? number of Ag atoms Example: A silver ring contains moles of silver. How many silver atoms silver are in the ring? 1 mole Ag atoms = x Ag atoms 2.5 x Ag atoms (2 sig. figs)

23 Information Given:1.234 x water molecules Find:? moles of water molecules Example: How many moles of water are in x water molecules? 1 mole water = x water molecules x moles water (4 sig. figs)

24 Mole, Atomic Mass, Mass The mass of exactly one mole of any element equals the Atomic Mass in grams. Example: Exactly 1 mole He = _______ g Exactly 1 mole Li = _______ g If given the mass of a particular number of atoms, we can determine the number of atoms in any mass of the element!

25 The Mass of one mole substance depends on the Element

26 Molar Mass The mass of one mole of atoms is called the Molar mass. Unit as g/mole or g/mol. The molar mass of an element, in grams, is numerically equal to the element’s atomic mass. Example: Molar mass of Sodium = ___________ Molar mass of Helium = ___________

27 Molar Mass as Conversion Factor Example: molar mass He = g 1 mole He = gram He So 1 mole He = gram He Given number of Moles  Mass Mass (gram) = _________________ Given Mass  Mole Mole = ___________________

28 Information Given:57.8 g S Find:? moles S Conv. Fact.: 1 mole S = g Example: Calculate the number of moles of sulfur in 57.8 g of sulfur 1.80 moles S (3 sig. figs)

29 Information Given: 3.34 x moles He Find:? Grams of He Conv. Fact.: 1 mole He = 4.00 g Example: Calculate the mass of 3.34 x mole of helium gas g He

30 Practice: #atoms, moles, molar mass The largest uncut diamond (pure carbon) weighs 755 carat (1 carat = 0.2 grams exactly). How many moles of carbon atoms are in this diamond? What is mass for 1.2 x mole gold? (optioinal) 70% of the mass of the Sun is hydrogen. The mass of the Sun is 1.99 x kg. How many moles of hydrogen atoms are in the Sun? 12.6 mol C 1.38 x mol H atom 0.24 g mol Au

31 Molar Mass and Avogadro’s Number Since 1 mole contains Avogadro’s number of units whilst has a mass of molar mass, there is direct connection/conversion factor between Avogadro’s number and molar mass. Example: x Al atoms = _______ g Al x He atoms = _______ g He

32 g Almole Alatoms Al Information Given:16.2 g Al Find:? atoms Al 1 mol Al = g = x Al atoms Example: How many aluminum atoms are in an aluminum can with a mass of 16.2 g? 3.62 x atoms Al

g Ag Given: 1.34 x Ag Find:? grams Ag 1 mol Ag = g Ag = x Ag atoms SM: atoms  mol  g Example: What is the mass of 1.34 x silver atoms?

34 Practice: Mass vs. Molec/Atom Diamond is made of pure carbon. The largest uncut diamond weighs 755 carat (1 carat = 0.2 grams exactly). How many carbon atoms are in this diamond? What is the mass of one gold atom in grams? 7.57 x C atoms x grams

35 Molar Mass of Compounds Molar Mass: Mass of molecules per exactly one mole of this molecule. Unit = g/mol Example: 1 mole of H 2 O = 2 moles H + 1 mole O Molar Mass of H 2 O = 2(1.008 g/mol H) g/mol O = g/mol 1 mole Al(NO 3 ) 3 = 1 mole Al + 3 mole N + 9 mole O Molar Mass of Al(NO 3 ) 3 = 1(26.98) + 3(14.01) + 9(16.00) = g/mol

36 Practice: Find the Molar Mass Sulfuric acid Aluminum sulfate Ammonium chlorite Hydrobromic acid Nickel(II) phosphate

Mass of Compound ↔ Moles of Compound

38 Information Given:1.75 mol H 2 O Find:? g H 2 O C F: 1 mole H 2 O = g H 2 O Example: Calculate the mass (in grams) of 1.75 mol of water 31.5 g H 2 O

39 Information Given:454 g CO 2 Find:? mol CO 2 C F: 1 mole CO 2 = g CO 2 Example: Calculate the mole of CO 2 in 454 g dry ice (solid carbon dioxide) mol CO 2

Mass of Compound ↔ Number of molecules

41 Information Given:4.8 x molec NO 2 Find:? g NO 2 1 mole NO g NO 2 Example: Find the mass of 4.8 x NO 2 molecules 3.7 x 10 2 g

42 Information Given:1.00 mL H 2 O Find:#H 2 O molecules 1 mole H 2 O = g H 2 O Example: How many water molecules in 1.00 mL DI water? 3.34 x H 2 O molecules Density of water = ______ g/mL

43 Practice Online: How many moles of water in mL pure water if the density of water is 1.00 g/mL? Determine the mass of 2.0 × 10 3 mole NaCl.

44 Chemical Formulas as Conversion Factors 1 spider  8 legs + 1 head + 1 abdomen 1 chair  4 legs + 1 seat + 1 back 1 H 2 O molecule  2 H atoms + 1 O atom

45 Mole Relationships in Chemical Formulas Given: #moles of the compound Chemical formula of the compound  #moles of a constituent element within the compound Moles of CompoundMoles of Constituents 1 mol NaCl1 mole Na, 1 mole Cl 1 mol H 2 O2 mol H, 1 mole O 1 mol CaCO 3 1 mol Ca, 1 mol C, 3 mol O 1 mol C 6 H 12 O 6 6 mol C, 12 mol H, 6 mol O

46 Quantities in Chemical Reactions Amount of every substance used and made in a chemical reaction is related to the amounts of all the other substances in the reaction Law of Conservation of Mass Reaction Stoichiometry: the study of the numerical relationship between chemical quantities in a chemical reactionStoichiometry Online interactive:

47 Recipe: Making Pancakes The number of pancakes you can make depends on the amount of the Ingredients you use Mathematically (as Conversion Factor) 1 cu flour  2 eggs  ½ tsp baking powder  5 pancakes 1 cup Flour + 2 Eggs + ½ tsp Baking Powder  5 Pancakes

48 More Pancakes? More Everything! Make more or less than 5 pancakes? The number of eggs determines the number of pancakes you can make Conversion Factor! assuming you have enough flour and baking powder Example: To make 20 pancakes, how many eggs we need? 1 cu flour  2 eggs  ½ tsp baking powder  5 pancakes

49 Mole Ratio in Chemical reaction: N 2 + 3H 2  2NH 3 Every 3 molecules of H 2 react with exactly 1 molecule of N 2 to produce exactly 2 molecules of NH 3

50 Making Molecules Mole-to-Mole Conversions Mole-to-Mole Conversions Balanced equation is the “recipe” for a chemical reaction, providing Conversion Factors for calculation. Equation 3 H 2 (g) + N 2 (g)  2 NH 3 (g) tells us that 3 molecules of H 2 react with exactly 1 molecule of N 2 and make exactly 2 molecules of NH 3 or 3 molecules H 2  1 molecule N 2  2 molecules NH 3 in this reaction since we count molecules by moles 3 moles H 2  1 mole N 2  2 moles NH 3

Example: Mole-to-Mole Conversions

moles H 2 O (2 SF) Example: The gas heaters in common household ultilize combustion of methane to produce heat:CH 4 + 2O 2  CO 2 + 2H 2 O How many moles of H 2 O result from the complete combustion of 3.4 mol of CH 4 ?

53 Example: The combustion of octane in engine produces CO 2 and water: 2C 8 H O 2  16CO H 2 O How many moles of H 2 O result from the of 3.4 mol of C 8 H 18 ? How many moles of CO 2 ? 31 mol water 27 mol CO2

54 More practice To produce 123. moles of ammonia, how many moles of hydrogen gas is needed in the reaction below? 3H 2 + N 2  2NH 3 To react with 123. moles of hydrogen, how many moles of nitrogen gas is needed in the reaction below? 3H 2 + N 2  2NH 3

55 Mass-to-Mass ConversionsMass-to-Mass Conversions in Chemical Reaction Relationship between Mass and Number of Moles of a chemical: Molar Mass 1 mole = Molar Mass in grams Molar Mass of the chemicals in the reaction + Balanced chemical equation : convert from the Mass of any chemical in the reaction to the Mass of any other

Example: Mass-to-Mass Conversions

57 Information Given:58.5 g CO 2 Find: g C 6 H 12 O 6 CF: 1 mol C 6 H 12 O 6 = g 1 mol CO 2 = g 1 mol C 6 H 12 O 6  6 mol CO 2 Example: How many grams of glucose can be synthesized from 58.5 g of CO 2 in the reaction? 6 CO 2 (g) + 6 H 2 O(l)  6 O 2 (g) + C 6 H 12 O 6 (aq) 39.9 g C 6 H 12 O 6

58 More Example: How many grams of H 2 O result from the complete combustion of 3000 g of C 8 H 18 (about 1.0 gallon)? How many grams of CO 2 ? 2C 8 H O 2  16CO H 2 O How are we contributing to greenhouse gas in the environment? 1 mol C 8 H 18 = g 1 mol CO 2 = mol H 2 O = g

59 More Example: Jessica wanted to neutralize her fresh orange juice (10% m/m) with baking soda (NaHCO 3 ). 3 NaHCO 3 + H 3 C 6 H 5 O 7  Na 3 C 6 H 5 O 7 + 3CO 2 + 3H 2 O How many grams of baking soda will she need to neutralize 10.0 g citric acid (in 1 liter juice)?? 1 mol H 3 C 6 H 5 O 7 = g 1 mol NaHCO 3 = g citric acid

60 Stoichiometry Practice – For the following equation, calculate the mass of 2 nd product when 1.23 g of 1 st reactant is consumed. 2HBr(aq) + K 2 SO 3 (aq)  H 2 O(l) + SO 2 (g) + 2 KBr(aq) 3K 2 CO 3 (aq) + 2(NH 4 ) 3 PO 4 (aq)  3(NH 4 ) 2 CO 3 (aq) + 2K 3 PO 4 (aq) Ba(OH) 2 (aq) + H 2 SO 4 (aq)  BaSO 4 (s) + 2H 2 O(l) Ca(OH) 2 (aq) + Li 2 CO 3 (aq)  CaCO 3 (s) + 2LiOH(aq) 60 Tro: Chemistry: A Molecular Approach, 2/e

61 Theoretical and Actual Yield To determine the theoretical yield, we should use reaction stoichiometry to determine the amount of product each of our reactants could make. The theoretical yield will always be the least possible amount of product. The theoretical yield will always come from the limiting reactant. Because of both controllable and uncontrollable factors, Actual yield < Theoretical yield.

Example: Finding Theoretical Yield and Percent Yield

63 = g C 6 H 12 O 6 = 39.9 g C 6 H 12 O 6 Sig. Figs. & Round: 1 mol C 6 H 12 O 6 = g 1 mol CO 2 = g 1 mol C 6 H 12 O 6  6 mol CO 2 Example: Plants ultilize photosynthesis to produce glucose. 6CO 2 (g) + 6H 2 O(l)  6O 2 (g) + C 6 H 12 O 6 (aq) How many grams of glucose can be synthesized from 58.5 g of CO 2 in the reaction?

64 More Example: How many grams of H 2 O result from the complete combustion of 3000 g of C 8 H 18 (about 1.0 gallon)? How many grams of CO 2 ? 2C 8 H O 2  16CO H 2 O How are we contributing to greenhouse gas in the environment?

65 Oxidation-Reduction Reaction (Redox reactions) metals react with nonmetals to form ionic compounds ionic compounds are solids at room temperature the metal loses electrons and becomes a cation the metal undergoes oxidation the nonmetal gains electrons and becomes an anion the nonmetal undergoes reduction In the reaction, electrons are transferred from the metal to the nonmetal 2 Na(s) + Cl 2 (g)  NaCl(s)

66 LEO the Lion go “GER” LEO: loses electron oxidation Ca  Ca e - GER: gain electrons reduction O + 2e -  O 2-

67 Redox reaction in Life Life on Earth: From Photosynthesis to Metabolism Modern civilization: Automobile engine (electric or gasoline) Battery Manufacture of metals such as aluminum and steel Chemical explosives Antioxidant

68 Write a Solution Map: g CO 2 Information Given:58.5 g CO 2 Find: g C 6 H 12 O 6 CF: 1 mol C 6 H 12 O 6 = g 1 mol CO 2 = g 1 mol C 6 H 12 O 6  6 mol CO 2 mol CO 2 mol C 6 H 12 O 6 g C 6 H 12 O 6 Example: How many grams of glucose can be synthesized from 58.5 g of CO 2 in the reaction? 6 CO 2 (g) + 6 H 2 O(l)  6 O 2 (g) + C 6 H 12 O 6 (aq)