Stoichiometric Calculations Slide 3 / 109 Slide 4 / 109 Table of - PDF document

Slide 1 / 109 Slide 2 / 109 Stoichiometric Calculations Slide 3 / 109 Slide 4 / 109 Table of Contents Stoichiometry Calculations Click on the topic to go to that section with Moles · Stoichiometry Calculations with Moles · Stoichiometry Calculations with Particles and Volume · Stoichiometry Calculations with Mass · Mixed Stoichiometry Problems · Limiting Reactants · Theoretical, Actual and Percent Yield · Calculating Excess Reactants Return to Table of Contents Slide 5 / 109 Slide 6 / 109 Stoichiometry Stoichiometry in our daily lives The word stoichiometry is derived from two Greek words. Airbags save thousands of lives every "stoicheion" meaning element and "metron", meaning measure. year. When a collision happens, the following reaction occurs. 2NaN 3 (s) --> 2Na(s) + 3N 2 (g) In order to properly inflate, roughly 50 L of nitrogen gas must be produced. NaN 3 capsule Engineers have determined, using stoichiometry, that about 96 grams of NaN 3 are needed to react in each airbag capsule to produce enough nitrogen gas.

Slide 7 / 109 Slide 8 / 109 Stoichiometric Calculations Stoichiometric Calculations A balanced chemical equation is needed to perform any stoichiometric calculations. The coefficients in the balanced equation give the ratio of moles of reactants and products. N 2 + 3H 2 ---> 2NH 3 2 H 2 + O 2 --# 2 H 2 O 1 mol N 2 3 mol H 2 1 mol N 2 can be read as: 3 mol H 2 2 mol NH 3 2 mol NH 3 2 moles of H 2 plus 1 mole of O 2 yields 2 moles of H 2 O The above ratios can be used to determine the quantity of any reactant and products. giving ratios of: For every 1 mol of N 2 , you would need 3 mol of H 2 to completely react with · 2 mol H 2 2 mol H 2 1 mol O 2 you would produce 2 mol of NH 3 1 mol O 2 2 mol H 2 O 2 mol H 2 O · Slide 9 / 109 Slide 10 / 109 Stoichiometry Calculations with Moles Stoichiometric Calculations with Moles 2 H 2 + O 2 2 H 2 O 1. Use the equation to set Using this interpretation it's straightforward to answer 2 mol H 2 O up a ratio of the substances questions about the relative number of moles of reactants of interest. 2 mol H 2 and products. 2. Set that equal to the ratio n mol H 2 O 2 mol H 2 O For instance, use the balanced equation below to determine = of the known to unknown 8 mol H 2 2 mol H 2 the maximum number of moles of H 2 O that could be created quantities of the same from reacting 8 moles of H 2 . substances. 2 H 2 + O 2 2 H 2 O 8(2) = (2) n mol H 2 O 3. Solve for the unknown. n = 8 mol H 2 O Slide 11 / 109 Slide 12 / 109 Stoichiometry Calculations with Moles Stoichiometry Calculations with Moles 2 H 2 + O 2 - -# 2 H 2 O Another Example: 1. Use the formula to set up 1 mol O 2 a ratio of the substances of 2 mol H 2 2 H 2 + O 2 2 H 2 O interest. Given the equation: 2. Set that equal to the ratio 1 mol O 2 n mol O 2 = of the known to unknown How many moles of oxygen would be needed to react with 12 mol H 2 2 mol H 2 quantities of the same 12 moles of H 2 ? substances. 12(1) = (2)n O 2 3. Solve for the unknown by cross multiplying. = 6 n O 2

Slide 13 / 109 Slide 14 / 109 Stoichiometry Calculations Real World Application 2 H 2 + O 2 -# 2 H 2 O 2Al + Fe 2 O 3 --> 2Fe + Al 2 O 3 + 859 kJ of energy Given 12 moles of H 2 , how much O 2 and H 2 O would be needed or The thermite reaction produced? (above) releases a lot of Using the ratios, you would need..... heat and is used in to weld railroad tracks together. 1/2 as much O 2 as H 2 (ratio is 1 mol O 2 /2 mol H 2 ) 12 mol H2 x 1 mol O 2 = 6 mol O 2 needed How many moles of Al would be needed to produce 7.8 moles of 2 mol H 2 Al 2 O 3 ? Using the ratios, you would produce..... An equal amount of H 2 O as H 2 used (ratio is 2 mol H 2 O/2 mol H 2 ) 12 mol H 2 x 2 mol H 2 O = 12 mol H 2 O move for 7.8 mol Al 2 O 3 x 2 mol Al = 15.6 mol Al 2 mol H 2 answer 1 mol Al 2 O 3 Slide 15 / 109 Slide 15 (Answer) / 109 What is the largest number of moles of Al 2 O 3 What is the largest number of moles of Al 2 O 3 1 1 that could result from reacting 6 moles of O 2 ? that could result from reacting 6 moles of O 2 ? 2 (g) - - # 2 Al 2 O 3 (s) 2 (g) - - # 2 Al 2 O 3 (s) 4 Al (s) + 3 O 4 Al (s) + 3 O Answer 4 [This object is a pull tab] Slide 16 / 109 Slide 16 (Answer) / 109 2 2 How many moles of O 2 would be required to How many moles of O 2 would be required to create 12 moles of Al 2 O 3 ? create 12 moles of Al 2 O 3 ? 2 (g) - - # 2 Al 2 O 3 (s) 2 (g) - - # 2 Al 2 O 3 (s) 4 Al (s) + 3 O 4 Al (s) + 3 O Answer 18 [This object is a pull tab]

Slide 17 / 109 Slide 17 (Answer) / 109 How many moles of O 2 would be required to How many moles of O 2 would be required to 3 3 completely react with 8 moles of Al? completely react with 8 moles of Al? 2 (g) - - # 2 Al 2 O 3 (s) 2 (g) - - # 2 Al 2 O 3 (s) 4 Al (s) + 3 O 4 Al (s) + 3 O Answer 6 [This object is a pull tab] Slide 18 / 109 Slide 18 (Answer) / 109 4 When iron rusts in air, iron (III) oxide is produced. 4 When iron rusts in air, iron (III) oxide is produced. How many moles of oxygen react with 2.4 mol of Fe How many moles of oxygen react with 2.4 mol of Fe in this reaction? in this reaction? 4 Fe (s) + 3 O 2 (g)--> 2 Fe 2 O 3 (s) 4 Fe (s) + 3 O 2 (g)--> 2 Fe 2 O 3 (s) Answer 1.8 [This object is a pull tab] Slide 19 / 109 Slide 19 (Answer) / 109 5 How many moles of aluminium are needed to react 5 How many moles of aluminium are needed to react completely with 1.2 mol FeO? completely with 1.2 mol FeO? 2 Al (s) + 3 FeO (s) --> 3 Fe (s) + Al 2 O 3 (s) 2 Al (s) + 3 FeO (s) --> 3 Fe (s) + Al 2 O 3 (s) Answer 0.8 [This object is a pull tab]

Slide 20 / 109 Slide 20 (Answer) / 109 6 How many moles of calcium metal are produced 6 How many moles of calcium metal are produced from the decomposition of 8 mol of calcium from the decomposition of 8 mol of calcium chloride? chloride? CaCl 2 (s) --> Ca (s) + Cl 2 (g) CaCl 2 (s) --> Ca (s) + Cl 2 (g) Answer 8 [This object is a pull tab] Slide 21 / 109 Slide 21 (Answer) / 109 7 How many moles (total) of calcium metal and 7 How many moles (total) of calcium metal and chlorine gas are produced from the chlorine gas are produced from the decomposition of 8 mol of calcium chloride? decomposition of 8 mol of calcium chloride? CaCl 2 (s) --> Ca (s) + Cl 2 (g) CaCl 2 (s) --> Ca (s) + Cl 2 (g) Answer 16 [This object is a pull tab] Slide 22 / 109 Slide 22 (Answer) / 109 8 How many moles of Ag are needed to react with 40 8 How many moles of Ag are needed to react with 40 moles of HNO 3 ? moles of HNO 3 ? 3 Ag(s) + 4 HNO 3 (aq) --> 3 AgNO 3 (aq) + 2 H 2 O(l) + NO(g) 3 Ag(s) + 4 HNO 3 (aq) --> 3 AgNO 3 (aq) + 2 H 2 O(l) + NO(g) Answer 30 [This object is a pull tab]

Slide 23 / 109 Slide 23 (Answer) / 109 9 How many moles of AgNO 3 could be produced from 9 How many moles of AgNO 3 could be produced from 40 moles of HNO 3 ? 40 moles of HNO 3 ? 3Ag(s) + 4HNO 3 (aq) --> 3AgNO 3 (aq) + 2 H 2 O(l) + NO(g) 3Ag(s) + 4HNO 3 (aq) --> 3AgNO 3 (aq) + 2 H 2 O(l) + NO(g) Answer 30 [This object is a pull tab] Slide 24 / 109 Slide 24 (Answer) / 109 10 How many moles of water would be produced when 10 How many moles of water would be produced when 0.4 moles of Ag react with an excess amount of 0.4 moles of Ag react with an excess amount of HNO 3 ? HNO 3 ? 3Ag(s) + 4HNO 3 (aq) --> 3AgNO 3 (aq) + 2 H 2 O(l) + NO(g) 3Ag(s) + 4HNO 3 (aq) --> 3AgNO 3 (aq) + 2 H 2 O(l) + NO(g) Answer 0.26 [This object is a pull tab] Slide 25 / 109 Slide 25 (Answer) / 109 11 How many moles of NO were produced if 16 moles of 11 How many moles of NO were produced if 16 moles of water were made during the reaction? water were made during the reaction? 3Ag(s) + 4HNO 3 (aq) --> 3AgNO 3 (aq) + 2 H 2 O(l) + NO(g) 3Ag(s) + 4HNO 3 (aq) --> 3AgNO 3 (aq) + 2 H 2 O(l) + NO(g) Answer 8 [This object is a pull tab]

Slide 26 / 109 Slide 26 (Answer) / 109 12 How many moles of N 2 H 4 are required to produce 57 12 How many moles of N 2 H 4 are required to produce 57 moles of nitrogen gas? moles of nitrogen gas? 2 N 2 H 4 (l) + N 2 O 4 (l) ---> 3 N 2 (g) + 4 H 2 O(g) 2 N 2 H 4 (l) + N 2 O 4 (l) ---> 3 N 2 (g) + 4 H 2 O(g) Answer 38 [This object is a pull tab] Slide 27 / 109 Slide 27 (Answer) / 109 13 How many moles of dinitrogen tetraoxide would be 13 How many moles of dinitrogen tetraoxide would be needed to produce 57 moles of nitrogen gas? needed to produce 57 moles of nitrogen gas? 2 N 2 H 4 (l) + N 2 O 4 (l) ---> 3 N 2 (g) + 4 H 2 O(g) 2 N 2 H 4 (l) + N 2 O 4 (l) ---> 3 N 2 (g) + 4 H 2 O(g) Answer 19 [This object is a pull tab] Slide 28 / 109 Slide 28 (Answer) / 109 14 How many moles of water are produced if 57 moles 14 How many moles of water are produced if 57 moles of nitrogen gas are produced? of nitrogen gas are produced? 2 N 2 H 4 (l) + N 2 O 4 (l) ---> 3 N 2 (g) + 4 H 2 O(g) 2 N 2 H 4 (l) + N 2 O 4 (l) ---> 3 N 2 (g) + 4 H 2 O(g) Answer 76 [This object is a pull tab]