3. Chapter 9 is Stoichiometry!! I can help you count moles!!!

4. Composition stoichiometry, which you studied in chapter three, involves mass relationships of elements within compounds. Reaction stoichiometry involves the mass relationships between reactants and products in a chemical reaction. In other words, you are converting amounts of one substance to amounts of another substance in a reaction. **All reaction stoichiometry questions start with a BALANCED CHEMICAL EQUATION!!!! The Art of Counting Without Counting

5. Reaction stoichiometry problems Easy as 1,2,3,4 1. Write the formula equation and balance it. 2. Convert grams of compound A to moles of compound A using the molar mass of compound A. 3. Use balanced equation to find the mole ratio (this is where you make the switch from compound A to compound B) 4. Convert moles of compound B to moles of compound B using the molar mass of compound B.

6. Conversions you will need to be able to understand and use: How many atoms (molecules or particles or chairs or Dalmatians) are in a mole? 6.02 X 10 23 How do you find how many grams are in a mole of a substance? Look at your periodic table!! Add up the masses of the elements in the compound! How many liters of a gas are in a mole? (this one is new) 1 mole of ANY gas = 22.4 Liters What is a mole ratio? (this one’s new, too) You must have a correctly balanced equation for this to be correct. ZnCl 2 + 3O 2 → Zn(ClO 3 ) 2 1 mole of ZnCl 2 3 mole O 2 1 mole of ZnCl 2 1 mole Zn(ClO 3 ) 2 3 moles of O 2 1 mole Zn(ClO 3 ) 2

7. Stoichiometry Roadmap grams of A liters of A (gases only) particles of A moles of Bmoles of A liters of B (gases only) grams of B particles of B Mole ratio / 22.4 LX 22.4 L / molar mass X molar mass / Avog. # X Avog. # / 22.4 LX 22.4 L / molar mass X molar mass / Avog. # X Avog. #

8. Example 1 Tin (II) fluoride, SnF 2, is used in some toothpastes. It is made by the reaction of tin with hydrogen fluoride according to the following equation: Sn(s) + 2HF → SnF 2 (s) + H 2 (g) How many grams of SnF 2 are produced from the reaction of 30.00 g of HF with Sn?

9. Sn(s) + 2HF → SnF 2 (s) + H 2 (g) Check the road map Grams A → mole A →mole ratio →mole B → grams B 30.00 g HF 1 mol HF1 mol SnF 2 156.71 g SnF 2 20.01 g HF2 mol HF 1 mol SnF 2 = 117.5 g SnF 2

10. Example 2 Laughing gas (nitrous oxide) is sometimes used as an anesthetic in dentistry. It is produced when ammonium nitrate is decomposed according to the following reaction: NH 4 NO 3 (s) → N 2 O (g) + 2H 2 0 (l) How many moles of NH 4 NO 3 are required to produce 33.0 g of N 2 O?

11. NH 4 NO 3 (s) → N 2 O (g) + 2H 2 0 (l) How many moles of NH 4 NO 3 are required to produce 33.0 g of N 2 O? Check the road map: Grams X → mol X → mole ratio → mol Y 33.0 g N 2 O 1 mol N 2 O 1 mol NH 4 NO 3 =.750 mol NH 4 NO 3 44.02 g N 2 O 1 mol N 2 O