1. Chapter 3 Stoichiometry Deals with quantities of materials consumed and produced in chemical reactions

2. Stoichiometry Terms Atomic Mass -Average value of the isotopes in a naturally occurring element -Sometimes called the atomic weight Mole - the number equal to the number of carbon atoms in exactly 12 grams of pure Carbon-12 - symbol is mol

3. Terms con. Avogadro’s Number - one mole of anything contains 6.022 x 10 23 units of that substance - Mass of 1 mol of an element= its atomic mass in grams - One mole of Al= 6.022 x 10 23 atoms of Al

4. Examples Determine the number of moles of atoms and the number of atoms I a 10.0 g sample of aluminum. Calculate the number of moles in a sample of cobalt containing 5.00 x 10 20 atoms and calculate the mass of the sample.

5. Molar Mass Mass in grams of 1 mole of the compound Example: Calcium carbonate(CaCO 3 ) is found in limestone, marble, and chalk. Determine its molar mass. If a sample contains 4.86 moles, determine its mass and the mass of carbonate ions present?

6. Another example Calculate the number of molecules in 1.058 moles of H 2 0.

7. Percent Compostion of Compounds Percent by mass of each element present in a compound 1. Determine the molar mass of the compound 2. Divide the mass of each element by the total molar mass Example: Determine the mass percent of each element in glucose, C 6 H 12 O 6.

8. Determining the Formula of a Compound Two Types of Formulas 1. Emperical formula - the simplest whole number ration of atoms in a compound 2. Molecular Formula - exact formula of a compound - molar mass of the compound is needed

9. Examples of Emperical and Molecular EmpericalMolecular H 2 O CH 2 O C 6 H 12 O 6

10. Determining the Emperical formula You need to convert % composition to empirical formula Percent to mass Mass to moles Divide by small Multiply ‘til whole

11. Example of Emperical Formula A compound consists of the following: 71.65 % Cl 24.27% C 4.07% H Determine its emperical formula.

12. Determining the Molecular Formula 1. Determine the emperical formula 2. Calculate the emperical formula mass 3. Divide the molar mass of the compound by the emperical formula mass 4. Multiply the emperical formula subscripts by this factor

13. Molecular formula example From a previous example, the empirical formula was ClCH 2. The molar mass of the compound is 98.96 g/mol. What is the molecular formula?

14. Chemical Equations Represents a chemical reaction showing the #’s of reactants and products Types of Info found in an Equation 1. Nature of the reactants/products Solid(s) Liquid(l) Gas(g) Dissolved in water(in aqueous solution)(aq) 2. Relative # of each reactant and product

15. Balancing Chemical Equations CH 4 + O 2  CO 2 + H 2 0 Coefficient- used to balance equations 1. Tells how many moles of reactants/products 2. Tells how many molecules involved in the reaction

16. Balancing examples Solid ammonium dichromate when ignited produces solid chromium(III) oxide, nitrogen gas, and water vapor. Write a balance equation. Ammonia gas, NH 3, reacts with oxygen gas to form gaseous nitric oxide, NO, and water vapor. Write a balanced equation.

17. Stoichiometric Calculations What mass of oxygen will react with 96.1 g of propane, C 3 H 8, to produce carbon dioxide and water vapor? 5 O 2 (g) + C 3 H 8 (g)  3 CO 2 (g)+ 4 H 2 O(g)

18. Calculations involving a Limiting Agent Limiting Reactant Reactant that is consumed first and limits the number of products Nitrogen gas can be prepared by passing gaseous ammonia over solid copper (II) oxide at high temperatures. The other products are solid copper and water vapor. If a sample containg 18.1 g of NH 3 is reacted with 90.4 g of CuO, which is the limiting agent? How many grams of N2 will be formed?

19. Calculating Percent Yield Theoretical Yield- amount of a product formed when a limiting reactant is completely consumed % yield= actual yield/theoretical yield 100

20. Percent yield example Methanol(CH 3 OH) can be manufactured by a combination of gaseous carbon monoxide and hydrogen. Suppose 68.5 kg CO(g) is reacted with 8.60 kg H 2 (g). Calculate the theoretical yield of methanol. If 3.57 x 10 4 g of methanol is actually produced, what is the % yield of methanol?