Chapter 5 Chemical Reactions

Table 4.2

The Mole

1 dozen eggs = 12 eggs 1 Gross pencils = 144 pencils 1 Ream of paper = 500 sheets of paper

The Mole 1 mole = 6.022 x 1023 things Avogadro’s number The number of carbon atoms in 12g of C-12 Abbreviation: “mol” How much does this weigh?

Cu, Al, Pb, S, Mg, Cr

Mole and Mass Relationships carbon 12.01 g 1 mole sulfur 32.06 g Tro's "Introductory Chemistry", Chapter 6

A Silver Ring Contains 1. 1 x 1022 Silver Atoms A Silver Ring Contains 1.1 x 1022 Silver Atoms. How Many Moles of Silver Are in the Ring? Calculate the Number of Atoms in 2.45 Mol of Copper

Molar Mass The mass, in grams, of one mole of any element or compound Abbreviated with capital, italicized MW Unit = grams/mole = g/mol Also called Formula Mass and Molecular Weight

Problems You need 0.250 mol Cu for an experiment, how many grams should you use? How many atoms of Cu is this? Calculate the number of moles of sulfur in 57.8 g of sulfur. Calculate the Moles of Carbon in 0.0265 g of Pencil Lead. How Many Aluminum Atoms Are in a Can Weighing 16.2 g? You have 145.9 g Hg. How many moles are present? If Hg has a density of 13.53 g/mL, what volume do you have?

Molar Mass of Compounds The relative weights of molecules can be calculated from atomic weights. Since 1 mole of H2O contains 2 moles of H and 1 mole of O. Molar mass = 1 mole H2O = 2(1.01 g H) + 16.00 g O = 18.02 g. Tro's "Introductory Chemistry", Chapter 6

1) Write the molecular formula for the compounds above. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ 1) Write the molecular formula for the compounds above. What are the molecular weights for the compounds above? Calculate the Mass of 1.75 Mol of H2O How Many Moles Are in 50.0 g of PbO2? (Pb = 207.2, O = 16.00) What Is the Mass of 4.78 x 1024 NO2 Molecules?

What is the mass of 1. 34 mole of the first compound (CO2) What is the mass of 1.34 mole of the first compound (CO2)? What is the mass of carbon in this sample? Calculate the Moles of Oxygen in 1.7 Moles of CaCO3. Find the Mass of Carbon in 55.4 g C10H14O (carvone) How many moles of Sodium Chloride are present in 9.29 g? How many moles of sodium are present in the sample? How many oxygen atoms are there in 5.62g of Carbon Dioxide?

Your nurse gives you 10. 0g morphine, C17H19NO3 , for pain Your nurse gives you 10.0g morphine, C17H19NO3 , for pain. How many moles is this? How many grams of oxygen are present in this dose of analgesic?

Chemical Equations H2 (g) + Cl2(g)  2 HCl (g) Reactants Product(s) Coefficient Physical State Subscript H2 (g) + Cl2(g)  2 HCl (g) Reactants Product(s)

Law of Conservation of Matter/Mass Matter is neither created, nor destroyed, but is merely rearranged The mass of the reactants must equal the mass of the products H2 (g) + Cl2(g)  2 HCl (g)

Balancing Chemical Equations Zn(s) + HCl(aq)  H2(g) + ZnCl2(aq) Write the unbalanced equation Balance the atoms of one element Choose another element and balance it Continue until all elements have the same number of atoms on both sides of the equation Check yourself

Table 4.2

Problems __ N2(g) + __ H2(g)  __ NH3(g) __ Fe(s) + __ Cl2(g)  __ FeCl3(s) __NH3(g) + __O2(g)  __NO(g) + __H2O(g) __C5H12(l) + __O2(g)  __CO2(g) + __H2O(g)

General Reactions Combination rxns: 2 or more substances react to form a single product 2 H2 + O2  2 H2O

Decomposition rxns: single substance decomposes into 2 or more products opposite of combination rxns 2 H2O  2 H2 + O2

Single replacement/displacement: one element reacts with a compound to form a new compound and release a new element 2 Na + 2 H2O  2 NaOH + H2

Exchange or Double replacement/displacement: an interchange of partners between two compounds Pb(NO3)2(aq) + K2CrO4(aq)  PbCrO4(s) + 2 KNO3(aq)

Combustion rxns: the burning of a compound, usually a hydrocarbon, in oxygen to form heat, carbon dioxide and water

Problems Balance the following equations and identify the type of reaction present. __C3H8(g) + __O2(g)  __CO2(g) + __H2O(g) __BaCl2(aq) + __Na2SO4(aq)  __BaSO4(s) + __NaCl(aq) __Fe(s) + __H2O(l)  __Fe3O4(s) + __H2(g) __Pt(s) + __F2(g)  __PtF4(l) __H3BO3(s)  __B2O3(s) + __H2O(l) __C4H10(g) + __O2(g)  __CO2(g) + __H2O(g)

Stoichiometry Problems If you have 10.0g C4H10 (butane), how many grams of water can you make upon combustion? How much O2 do you need in problem 1 if you’d like to produce 7.39g CO2? How much CO2 is produced upon combustion of 4.3g of propane (C3H8)?

__C6H12O6(s) + __O2(g)  __CO2(g) + __H2O(l) Using the equation below, calculate the amount of glucose you started with if you produced 12.76g CO2? How much glucose was consumed in order to produce 100.0 mL of H2O? __C6H12O6(s) + __O2(g)  __CO2(g) + __H2O(l)

Limiting Reagent Limiting Reagent/Reactant/Factor: the reactant/factor that determines the amount of product formed Other reactants are “in excess” Cheaper reactants are usually in excess

Problems You have 10.0 moles H2 and 1.00 mol O2. How much H2O can you make? You combust 10.2 mol propane in 7.80 mol O2. How much CO2 can you produce?

If 2. 3 mol carbon disulfide reacts with 5 If 2.3 mol carbon disulfide reacts with 5.4 mol oxygen to form carbon dioxide and sulfur dioxide, what mass of sulfur dioxide is formed? 5.50 g silicon dioxide reacts with 4.71g Carbon to from silicon carbide and carbon monoxide. What mass of carbon monoxide is formed?

Percent Yield Theoretical Yield: the maximum possible quantity of product 100% yield Actual/Experimental Yield: quantity of product actually obtained Percent Yield: efficiency of reaction PY = (actual yield/theoretical yield) x 100

Problems From the previous question, the theoretical yield of CO is 5.13 g. If you obtained 4.32g CO, what was your % yield? You react 4.41 mol carbon monoxide with 8.39 mol hydrogen gas to get 122g methanol. What is your percent yield?