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Chapter 9.2 : Ideal Stoichiometric Calculations

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Chapter 9.2 : Ideal Stoichiometric Calculations

1. 1. Ideal Stoichiometric calculations<br />Chapter 9.2<br />
2. 2. Objectives:<br />Calculate the amount in moles of a reactant or product from the amount in moles of a different reactant or product.<br />Calculate the mass of a reactant or product from the amount in moles of a different reactant or product.<br />Calculate the amount in moles of a reactant or product from the mass of a different reactant or product.<br />Calculate the mass of a reactant or product from the mass of a different reactant or product.<br />
3. 3. Ideal Stoichiometric solutions<br />Importance of chemical equation<br />Mole ratio is obtained directly from it<br /><ul><li>Ideal conditions
4. 4. Reactants are completely converted to products
5. 5. Theoretical, and hardly ever met in laboratory setting
6. 6. Yet,ideal stoichiometry will tell you the maximum amount of product that can be formed.</li></li></ul><li>Conversions of Quantities in Moles<br />Problem type 1:<br />mol A mol B<br />Conversion factor is mole ratio<br />Must have a correctly balanced equation<br />Step 1:<br />Label two rows with mass and moles<br />2 H2 + O2 2 H2O<br />mass<br />Step 2:<br />Write down what is given : in this case we’ll say 2.00 mol of O2<br />2 mol<br />2.oo mol<br /> 4.00 mol<br />moles<br />Step 3:<br />1 mol<br />Map out to what you are looking for: in this case we’ll look for moles of H2O<br />Step 4:<br />Step 5:<br />Use mole ratio from coefficients<br />Calculate by multiplying the top and dividing from bottom<br />
7. 7. Sample Problem 1<br />In a spacecraft, the carbon dioxide, exhaled by astronauts can be removed by its reaction with lithium hydroxide, LiOH, according to the following chemical equation.<br /> CO2(g) + 2 LiOH(s) Li2CO3(s) + H2O(l)<br />How many moles of lithium hydroxide are required to react with 20 mol of CO2, the average amount exhaled by a person each day.<br />CO2(g) + 2 LiOH(s) Li2CO3(s) + H2O(l)<br />mass<br />2<br />moles<br />20 mol<br />40 mol<br />1<br />
8. 8. Conversions: Moles to Mass<br />Problem type 2:<br />mol A mol B mass B<br />Conversion factor is mole ratio and molar mass<br />Now find the mass of H2O<br />2 H2 + O2 2 H2O<br />72.1 g<br />mass<br /> x 18.02 g/mol<br />2 mol<br />2.oo mol<br /> 4.00 mol<br />moles<br />1 mol<br />Extra steps:<br />1. Map out till you get what you are looking for.<br />2. Convert using molar mass.<br />
9. 9. Sample Problem 2<br />In photosynthesis, plants use energy from the sun to produce glucose, C6H12O6, and oxygen from the reaction of carbon dioxide and water. What mass, in grams, of glucose is produced when 3.00 mol of water react with carbon dioxide?<br />CO2(g) + H2O(l) C6H12O6(s) + O2(g)<br />6<br />6<br />6<br />mass<br />90.1 g<br />x 180.18 g/mol<br />1<br />3.00 mol<br />0.500 mol<br />moles<br />6<br />C 6 x 12.01 = 72.06 g<br />H 12 x 1.01 = 12.12 g<br />O 6 x 16.00 = 96.00 g<br /> 180.18 g/mol<br />
10. 10. Sample Problem 3<br />What mass of carbon dioxide, in grams, is needed to react with 3.00 mol of H2O in the photosynthetic reaction described in the last sample problem?<br />CO2(g) + H2O(l) C6H12O6(s) + O2(g)<br />6<br />6<br />6<br />mass<br />132 g<br />90.1 g<br />x 180.18 g/mol<br />x 44.01 g/mol<br />1<br />6<br />3.00 mol<br />0.500 mol<br />moles<br />3.00 mol<br />6<br />6<br />
11. 11. Conversions of Mass to Amounts in Moles<br />Problem type 3:<br />mass A mol A mol B<br />Conversion factor is mole ratio and molar mass<br />Sample Problem 4<br />The first step in the industrial manufacture of nitric acid is the catalytic oxidation of ammonia. The reaction is run using 824 g of NH3 and excess oxygen. How many moles of NO and H2O are formed?<br />NH3(g) + O2 (g) NO(g) + H2O(g)<br />4<br />4<br />6<br />5<br />mass<br />824 g<br />÷ 17.04<br />4<br />6<br />48.4 mol<br />72.6 mol<br />moles<br />48.4 mol<br />4<br />4<br />
12. 12. Mass – Mass Calculations<br />Problem type 4:<br />mass A mol A mol B mass B<br />Conversion factor is mole ratio and molar mass<br />Sample Problem 5<br />Tin(II) fluoride,SnF2, is used in some toothpastes. It is made by the reaction of tin with hydrogen fluoride. How many grams of SnF2 are produced from the reaction of 30.00 g of HF with Sn?<br />Sn(s) + HF(g) SnF2(s) + H2 (g)<br />2<br />30.00 g<br />117.5 g<br />mass<br />÷ 20.01 g/mol<br />x 156.71 g/mol<br />1<br />1.500 mol<br />0.7500 mol<br />moles<br />2<br />