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1 Like a recipe: Balancing Eqns Reactants Products 2H 2 (g) + O 2 (g) 2H 2 O(l) coefficients subscripts Balancing Eqns Balancing Symbols (s) (l) (aq) (g) or Yields or Produces solid liquid (pure liquid) aqueous (dissolved in water) gas Copper(II) Chloride reacts with Iron(III) Sulfate to form Copper(II)Sulfate and Iron(III) Chloride Aluminum nitrate reacts with Sodium hydroxide to form Aluminum hydroxide and Sodium nitrate Some Types of Reactions Some Types of Reactions 1. Synthesis Al + Cl 2 AlCl 3 CaO(s) + CO 2 (g) CaCO 3 (s) 2. Decomposition HgO(s) Hg(l) + O 2 (g) CaCO 3 (s) CaO(s) + CO 2 (g) 3. Combustion Fe + O 2 Fe 2 O 3 C 4 H 10 + O 2 CO 2 + H 2 O 4. Other Types Single Replacement Double Replacement 1

2 Know your reactions well!!!! Stoichiometry Mole 1 dozen = 12 items 1 mole = X atoms/molecules 1 gram hydrogen = X atoms of hydrogen Stoichiometry Stoichiometry Grams Atoms 1 g H 1 mole H 6.02 X atms 2 g H 12 g C 36 g C 48 g O Grams Molecules Atoms 16 g CH 4 8 g CH 4 88 g CO g Ba(NO 3 ) 2 2

3 Molar Mass 1. Molar Mass = mass of one mole 2. Element= atomic mass 1 mole of O = 16.0 grams 3. Molecule or Compound sum of all the atoms Molar Mass GMA Calculate the molar mass of Barium O 2 BaCl 2? Fe 2 (SO 4 ) 3? Grams Atoms 1. How many C atoms are present in 18.0 g? (Ans: 9.03 X C) 2. What is the mass of 1.20 X atoms of Na? (Ans: 45.8 grams) GMA 3. What is the mass of 1.51 X atoms of Be?(Ans: 2.26 g) 5. How many atoms and grams are in mol of Radium? (Ans: 90.4 g, 2.41 X atoms) 1. Monoatomic Elements (C, Fe, Au) GMA 2. Molecules and Ionics (H 2 O, CaCl 2, O 2 ) 3

4 3. Molecules and formula units work the same when converting Molecules = Molecular Comps Formula Units = Ionic Compounds G M M A 1. How many calcium and chlorine atoms are in grams of Calcium Chloride? (Ans: 2.17 X atoms Cl) 2. How many hydrogen and oxygen atoms are in 3.60 grams of H 2 O? (Ans: 2.41 X atoms H) 3. Given 3.01X10 24 molecules of SO 3, find everything else. 4. Given 3.01 X molecules of Iron(III)bromide, find everything else. Mixed Examples Mixed Examples 1. How many carbon atoms are in 36.0 grams of carbon (1.81 X ) 2. How many carbon atoms are in 36.0 grams of C 2 H 6? (Ans:1.45 X atoms of C) Homework Problems (find everything else) a) 10.0 g C b) 10.0 g C 2 H 6 c) 4.0 X atoms of S d) 4.0 X molecules of SO 2 e) 0.44 moles of SO 2 4

5 Empirical Formula Empirical Formula 1. Empirical formula - simplest ratio of the elements in a compound 2. Formula Empirical Form. C 2 H 2 Al 4 S 6 C 6 H 12 O 6 C 12 H 24 O What is the EF of a compound that has g Ca and 1.60 g Cl? Rules - Go to moles - Divide by the smaller Empirical Formula Molecular Formula 2. What is the EF of a compound that is 66.0 % Ca and 34.0% P? 3. What is the EF of a compound that is 43.7 % P and 56.3 % O? 1. Empirical ratios of the elements 2. Molecular true number of each element Molecular Formula Molecular Formula EF CH 2 O MF CH 2 O (30 g/mol) C 2 H 4 O 2 (60 g/mol) C 3 H 6 O 3 (90 g/mol) C 4 H 8 O 4 (120 g/mol) 1. What is the MF of benzene if it has an EF of CH and a molar mass of 78.0 g? 2. What is the MF of a compound that is 40.9% C, 4.58 % H and 54.5 % O? It has a molar mass between 350 and 360 g/mol. 5

6 Reaction Stoich. Reaction Stoich. What coefficients mean: 2 Na + Cl 2 2NaCl 2 Na 1 Cl 2 2NaCl 4 Na 6 Na 2 Na + Cl 2 2NaCl 4 Cl 2 2 moles Na 10 moles Na ONLY WORKS FOR MOLES AND MOLECULES Reaction Stoich. Reaction Stoich. 1. How many moles of H 2 and O 2 must react to form 6 moles of H 2 O? 2. How many moles of KCl and O 2 are formed from the decomposition of 6 moles of KClO 3? 3. How many grams of oxygen are needed to react with 14.6 g of Na to form Na 2 O? (Ans: 5.08 g) 4. How many grams of P 4 and O 2 are needed to make 3.62 g of P 2 O 5? (Ans: 1.58 g, 2.04 g) Reaction Stoich. 5. What mass of oxygen is needed to react with 16.7 g of iron to form Iron(III)oxide? (Ans: 7.18 g) Calculate the mass of sodium bromide and oxygen that are formed from the decomposition of 50.0 grams of sodium bromate (NaBrO 3 ). 4Fe + 3O 2 2Fe 2 O 3 (34.1 g NaBr, 15.9 g O 2 ) 6

7 1. Sandwich analogy: 13 slices of bread 4 pieces of turkey Maximum # of sandwiches? 1. How many grams of H 2 SO 4 can be formed from the rxn of 5.00 moles of SO 3 and 2.00 moles of H 2 O? SO 3 + H 2 O H 2 SO 4 2. Totally consumed in a reaction. No leftovers (Ans: 196 g) 1. How many grams of H 2 O can be formed from the rxn of 6.00 moles of H 2 and 4.00 moles of O 2? O 2 + H 2 H 2 O 2. How many grams of NaCl can be formed from the reaction of mol of Na and mol of Cl 2? 2Na + Cl 2 2NaCl (Ans: 11.7 g) 3. How many grams of Ag can be formed from the rxn of 2.00 g of Zn and 2.50 g of silver nitrate? How much excess reactant remains? Zn + AgNO 3 Ag + Zn(NO 3 ) 2 (Ans: 1.59 g Ag, 1.52 g xs zinc) 4. How many grams of Ba 3 (PO 4 ) 2 can be formed from the rxn of 3.50 g of Na 3 PO 4 and 6.40 g of Ba(NO 3 ) 2? Na 3 PO 4 + Ba(NO 3 ) 2 Ba 3 (PO 4 ) 2 + NaNO 3 (Ans: 4.92 g) 7

8 Percent Yield 6. How many grams of Ag 2 S can be formed from the rxn of 15.6 g of Ag and 2.97 g of H 2 S? (Assume O 2 is in excess) 4Ag + 2H 2 S + O 2 2Ag 2 S + 2H 2 O (Ans: 18.1 g) A. Formula: Actual Yield Theoretical Yield X 100 = % Yield Percent Yield Percent Yield 1. What is the % yield if you start with grams of C and obtain 1.49 g of H 2 gas? C + H 2 O CO + H 2 2. Carbon was heated strongly in sulfur(s 8 ) to form carbon disulfide. What is the percent yield if you start with g of sulfur and collect 12.5 g of CS 2? 4C + S 8 4CS 2 (Ans: 89.4%) (Ans: 78.0%) Percent Yield grams of CO 2 were formed from the rxn of 40.0 g of CH 3 OH and 46.0 g of O 2. What is the % yield? 2CH 3 OH + 3O 2 2CO 2 + 4H 2 O (ANS: 87%) 8

9 In this experiment, magnesium chloride was prepared and its empirical formula was compared to the accepted formula of MgCl 2. To prepare magnesium chloride, 0.40 grams of magnesium powder was combined with 10 ml of 0.10 M HCl. The mixture was allowed to react, and heated to dryness. The mass of the resulting crystals was used to calculate the empirical formula. The average calculated formula of MgCl 1.8 had a 10% error and a range was 0.40 chlorine atoms. This procedure was not effective because while it was accurate, it was not precise. 8a) SO 3 + H 2 O H 2 SO 4 b) B 2 S 3 + 6H 2 O 2H 3 BO 3 + 3H 2 S c) 4PH 3 + 8O 2 6H 2 O + P 4 O 10 d) 2Hg(NO 3 ) 2 2HgO + 4NO 2 + O 2 e) Cu + 2H 2 SO 4 CuSO 4 + SO 2 + 2H 2 O 12.a) a) b) b) c) c) d) d) e) e) f) g) a) 4Al + 3O 2 2Al 2 O 3 b) Cu(OH) 2 CuO + H 2 O c) C 7 H O 2 7CO 2 + 8H 2 O d) 2C 5 H 12 O + 15O 2 10CO H 2 O a) 44.0 g/mol b) g/mol c) 58.3 g/mol d) 60.0 g/mol e) amu g/mole 92.3% C g/mole 4.5% H g/mole 6.1% H g/mole 65.01% Pt g/mole 11.8% O g/mole 70.8 % C 46 a)k 3 PO 4 b) Na 2 SiF 6 c) C 12 H 12 N 2 O 3 48 a) H 2 C 2 O 4 b) C 4 H 8 O 2 50 a) C 13 H 18 O 2 b) C 5 H 14 N 2 c) C 9 H 13 O 3 N 9

10 58.a) mol CO 2 b) 14.7 g C 6 H 12 O 6 c) 7.16 g CO a) mol Fe 2 O3 b) 78.9 g CO c) 105 g Fe d) 229 g= 229 g 48.a) H 2 C 2 O 4 b) C 4 H 8 O a) C 13 H 8 O 2 b)c 5 H 14 N 2 c) C 9 H 13 O 3 N 58.a) mol CO 2 b) 14.7 g C 6 H 12 O 6 c) 7.18 g CO 2 60.a) Fe 2 O 3 + 3CO 2Fe + 3CO 2 b) 78.9 g CO 2 c) 124 g CO 2 d) 229 g = 229 g 62.a) CaH 2 + 2H 2 O Ca(OH) 2 + 2H 2 b) g CaH2 64. a) 15.6 mol O 2 b) 35.0 g O 2 c) g mol Al 2 (SO 4 ) 3 form mol Al(OH) 3 react mol AL(OH) 3 remain 74.a) O 2 is limiting reactant b) 1.86 g H 2 O produced c) g NH 3 remain d) 4.25 g = 4.25 g g H 2 SO g PbSO g HC 2 H 3 O C 2 H 6 + Cl 2 C 2 H 5 Cl + HCl 232 g C 2 H 5 Cl (theoretical yield) 88.8% yield 80. Actual yield of Na 2 S = 1.80 g (1.95 g is the theoretical yield) The atmosphere of Jupiter is composed almost entirely of hydrogen (H 2 ) and helium (He). If the average molar mass of Jupiter s atmosphere is g/mole, calculate the percent composition. 10

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