1CHAPTER THREE CHEMICAL EQUATIONS & REACTION STOICHIOMETRY2Chemical Equations• A view from a molecular model perspective.3Chemical Equations Law of Conservation of Matter  There is no detectable change in quantity of matter in an ordinary chemical reaction. Balanced chemical equations must always include the same number of each kind of atom on both sides of the equation. This law was determined by Antoine Lavoisier.4Law of Conservation of MatterBalancing Equation ExamplesBalancing Equation ExamplesExample 1: Solid PExample 1: Solid P44will react with chlorine gas to will react with chlorine gas to produce solid PClproduce solid PCl55..PP44(s) + Cl(s) + Cl22(g) (g) ÆÆPClPCl5 5 (s)(s)5Chemical Equations Propane,C3H8, burns in oxygen to give carbon dioxide and water.38 2 2 2C H O CO H O∆+→+A combustion reaction6Chemical Equations Liquid C6H14burns in oxygen gas to form carbon dioxide gas and water vapor.614 2 2 2C H (l) + O ( ) CO (g) + H O (g)g∆→7Chemical Equations NH3gas burns in pure oxygen to form NO gas & water vapor. (A combustion reaction.)8Chemical Equations Aqueous cobalt(III) nitrate reacts with aqueous ammonium sulfide to produce solid cobalt(III) sulfide and aqueous ammonium nitrate. Write a balanced chemical equation for this reaction.9Chemical Equations Solid iron(III) oxide reacts with carbon monoxide to produce solid iron metal and carbon dioxide gas.23 2Fe O (s) + CO (g) Fe (s) + CO ( )g∆→10Calculations Based on Chemical Equations Can work in moles, formula units, etc. Frequently, we work in mass or weight (grams or kg or pounds or tons).23 2Fe O + 3 CO 2 Fe + 3 CO∆→11Chemical Equations Look at the information an equation provides:reactants yields products1 formula unit 3 molecules 2 atoms 3 molecules1 mole 3 moles 2 moles 3 moles159.7 g 84.0 g 111.7 g 132 g Fe O + 3 CO 2 Fe + 3 CO23 2∆→12Calculations Based on Chemical Equations Example 3-1: How many CO molecules are required to react with 25 formula units of Fe2O3?232325 f.w. Fe O3 CO molecules75 molecules of CO1 Fe O f.w.=13Calculations Based on Chemical Equations Example 3-2: How many iron atoms can be produced by the reaction of 2.50 x 105 formula units of iron (III) oxide with excess carbon monoxide?5232352.50 10 f.w. Fe O2 Fe atoms1 f.w. Fe O = 5.00 10 Fe atoms×=×14Calculations Based on Chemical Equations Example 3-3: What mass of CO is required to react with 146 g of iron (III) oxide?23 2323 23146 g Fe O 1 mol Fe O 3 mol CO 28.0 g CO159.7 g Fe O 1 mol Fe O 1 mol CO76.8 g CO ==15Calculations Based on Chemical Equations Example 3-4: What mass of carbon dioxide can be produced by the reaction of 0.540 mole of iron (III) oxide with excess carbon monoxide?23 2 223 220.540 mol Fe O 3 mol CO 44.0 g CO1 mol Fe O 1 mol CO= 71.3 g CO=16Calculations Based on Chemical Equations23 23222223231mol Fe O 159.7 g Fe O8.65 g CO 1 molCO 44.0 g CO 3 mol CO 1 mol Fe O10.5 g Fe O =  = Example 3-5: What mass of iron (III) oxide reacted with excess carbon monoxide if the carbon dioxide produced by the reaction had a mass of 8.65 grams? 17Calculations Based on Chemical Equations Example 3-6: How many pounds of carbon monoxide would react with 125 pounds of iron (III) oxide? 18Calculations Based on Chemical Equations23 23 2323 2323125 lb Fe O 454 g Fe O 1 mol Fe O1 lb Fe O 159.7 g Fe O3 mol CO 28 g CO 1 lb CO1 mol Fe O 1 mol CO 454 g CO65.7 lb CO   ==YOU MUST BE PROFICIENT WITH THESE TYPES OF PROBLEMS!!!19Limiting Reactant Concept Kitchen example of limiting reactant concept.1 box of muffin mix + 2 eggs + 1 cup of milk Æ 12 muffins How many muffins can we make with the following amounts of mix, eggs, and milk?20Limiting Reactant ConceptMix boxes Eggs Milk Limiting1 1 dozen 1 gallon (mix)4 1 dozen 1 gallon (mix)6 1 dozen 1 gallon (mix)8 1 dozen 1 gallon (eggs)1 box of muffin mix + 2 eggs + 1 cup of milk Æ 12 muffins16 cups = 1 gal21Limiting Reactant Concept Look at a chemical limiting reactant situation.Zn + 2 HCl→ ZnCl2+ H222Limiting Reactant Concept Example 3-8: What is the maximum mass of sulfur dioxide that can be produced by the reaction of 95.6 g of carbon disulfide with 110. g of oxygen? (Is this reaction balance?)22 2 2CS O CO SO+→ +23Limiting Reactant Concept Example 3-8: What is the maximum mass of sulfur dioxide that can be produced by the reaction of 95.6 g of carbon disulfide with 110. g of oxygen?CS O CO 2 SO1 mol 3 mol 1 mol 2 mol76.2 g 3(32.0 g) 44.0 g 2(64.1 g)22 2 2+→ +324Limiting Reactant ConceptExample 2: What is the maximum mass of sulfur dioxide that can be produced by the reaction of 95.6 g of carbon disulfide with 110. g of oxygen?2222:96.0 1.2676.2 1mass ratio of reactants from balanced equationgO gOgCS gCS=2222:110. 1.1595.6 1mass ratio of reactants givengO gOgCS gCS=We do not have enough oxygen. Therefore, oxygen is the limiting reactant.25Limiting Reactant Concept22 2 2CS 3 O CO 2 SO+→+2222110 g O 128.2g SO147 g SO96.0 g O=76.2 g 96 g 44.0 g 128.2g26Limiting Reactant Concept another approach22 2 222 2 222222 22 3 2 76.2 g 96 g 44.0 g 128.2g95.6 1 2 64.1 161 76.2 1 1 110 1 2 32.0 CS O CO SOg CS mol CS mol SO g SOgSOgmolCSmolSOgO molO molSOgO+→+ =  222264.1 147 3 1 gSOgSOmol O mol SO =  • Which is limiting reactant?– Limiting reactant is O2.• What is maximum mass of sulfur dioxide?– Maximum mass is 147 g.27Limiting Reactant Concept A mixture of 13.1 g Zn and 22.0 g I2is reacted to completion in a closed, evacuated container. What are the contents of the container after this reaction?Zn + I2Æ ZnI2We will solve this one in