Stoichiometry Chemical Calculations Chapter 12 Proportional Relationships 2

Stoichiometry Chemical Calculations Chapter 12

Proportional Relationships 2 1/4 c. flour 1 tsp. baking soda 1 tsp. salt 1 c. butter 3/4 c. sugar 3/4 c. brown sugar 1 tsp vanilla extract 2 eggs 2 c. chocolate chips Makes 5 dozen cookies. l I have 5 eggs. How many cookies can I make? 5 eggs 5 doz. 2 eggs Ratio of eggs to cookies = 12. 5 dozen cookies

Proportional Relationships l Stoichiometry ¡ Calculation of quantities in chemical reactions ¡ based on the mole ratio l Mole Ratio ¡ indicated by coefficients in a balanced equation 2 Mg + O 2 2 Mg. O

Stoichiometry Steps 1. Write a balanced equation. 2. Identify known & unknown. 3. Line up conversion factors. ¡ Mole ratio ¡ Molar mass ¡ Molar volume - moles moles grams moles liters gas Core step in all stoichiometry problems!! 4. Check answer.

Mole-Mole Problems l How many moles of KCl. O 3 must decompose in order to produce 9 moles of oxygen gas? 2 KCl. O 3 2 KCl + 3 O 2 ? mol 9 mol O 2 2 mol KCl. O 3 3 mol O 2 9 mol = 6 mol KCl. O 3

Mole-Mole Practice l How many moles of ammonia are produced when 0. 60 mol of nitrogen reacts with hydrogen? 1. 2 mol NH 3 l How many moles of aluminum are needed to form 3. 7 mol Al 2 O 3 according to the following equation? 4 Al(s) + 3 O 2(g) → 2 Al 2 O 3(s) 7. 4 mol Al

Mass-Mass Problems l How many grams of silver will be formed from 12. 0 g copper? Cu + 2 Ag. NO 3 2 Ag + Cu(NO 3)2 ? g 12. 0 g Cu 1 mol Cu 2 mol Ag 107. 87 g Ag 63. 55 g Cu 1 mol Ag = 40. 7 g Ag

Mass-Mass Practice l Calculate the number of grams of NH 3 produced by the reaction of 5. 40 g of hydrogen with an excess of nitrogen. 31 g NH 3 l Acetylene gas, C 2 H 2, is produced by adding water to calcium carbide. Ca. C 2(s) + 2 H 2 O(l) → C 2 H 2(g) + Ca(OH)2(aq) How many grams of acetylene are produced by adding water to 5. 00 g of Ca. C 2? 2. 03 g C 2 H 2

Other Stoichiometric Problems l How many grams of KCl. O 3 are req’d to produce 9. 00 L of O 2 at STP? 2 KCl. O 3 2 KCl + 3 O 2 ? g 9. 00 L O 2 1 mol O 2 2 mol 122. 55 KCl. O 3 g KCl. O 3 22. 4 L O 2 3 mol O 2 1 mol KCl. O 3 = 32. 8 g KCl. O 3

Other Stoichiometric Problems l How many grams of Cu are required to react with 1. 5 L of Ag. NO 3 at STP? Cu + 2 Ag. NO 3 2 Ag + Cu(NO 3)2 ? g 1. 5 L Ag. NO 3 1. 5 L 1 mol Ag. NO 3 1 mol Cu 22. 4 L 2 mol Ag. NO 3 63. 55 g Cu = 2. 1 g 1 mol Cu Cu

Other Stoichiometric Practice l Assuming STP, how many liters of oxygen are needed to produce 19. 8 L SO 3 according to this balanced equation? 2 SO 2(g) + O 2(g) → 2 SO 3(g) 9. 90 L O 2 l How many milliliters of nitrogen dioxide are produced when 3. 4 m. L of oxygen reacts with an excess of nitrogen monoxide at STP? 2 NO(g) + O 2(g) → 2 NO 2(g) 6. 8 m. L NO 2