CHEM 101PowerpointsWeek Ending 2/17/2012Chapter 3Part 2
3.6g CO2 mol CO2 mol C g Cg H2O mol H2O mol H g Hg of O = g of sample – (g of C + g of H)Combust 11.5 g ethanolCollect 22....
A process in which one or more substances ischanged into one or more new substances is achemical reactionA chemical equati...
Anatomy of a Chemical EquationCH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)
Anatomy of a Chemical EquationReactants appear on the leftside of the equation.CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)
Anatomy of a Chemical EquationProducts appear on the rightside of the equation.CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)
Anatomy of a Chemical EquationThe states of the reactants and products arewritten in parentheses to the right of eachcompo...
Anatomy of a Chemical EquationCoefficients are inserted tobalance the equation.CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)
Subscripts and Coefficients GiveDifferent Information• Subscripts tell the number of atoms ofeach element in a molecule
Subscripts and Coefficients GiveDifferent Information• Subscripts tell the number of atoms ofeach element in a molecule• C...
3.73 ways of representing the reaction of H2 with O2 to form H2Oreactants productsSummary of a Chemical Equation
How to “Read” Chemical Equations2 Mg + O2 2 MgO2 atoms Mg + 1 molecule O2 makes 2 formula units MgO2 moles Mg + 1 mole O2 ...
Balancing Chemical Equations1. Write the correct formula(s) for the reactants on theleft side and the correct formula(s) f...
Balancing Chemical Equations3. Start by balancing those elements that appear in onlyone reactant and one product.C2H6 + O2...
Balancing Chemical Equations4. Balance those elements that appear in two or morereactants or products.3.72 oxygenon left4 ...
Balancing Chemical Equations5. Check to make sure that you have the same number ofeach type of atom on both sides of the e...
© 2009, Prentice-Hall, Inc.Stoichiometric CalculationsThe coefficients in the balanced equation give theratio of moles of ...
© 2009, Prentice-Hall, Inc.Stoichiometric CalculationsStarting with the massof Substance A youcan use the ratio ofthe coef...
1. Write balanced chemical equation2. Convert quantities of known substances into moles3. Use coefficients in balanced equ...
Methanol burns in air according to the equation2CH3OH + 3O2 2CO2 + 4H2OIf 209 g of methanol are used up in the combustion,...
LimitingReactants
How Many Cookies Can I Make?• You can make cookiesuntil you run out of oneof the ingredients• Once this family runs outof ...
How Many Cookies Can I Make?• In this example the sugarwould be the limitingreactant, because it willlimit the amount ofco...
Limiting ReactantsThe limiting reactant isthe reactant present inthe smalleststoichiometric amount
Limiting Reactants• The limiting reactant is the reactant present in thesmallest stoichiometric amount– In other words, it...
Limiting ReactantsIn the example below, the O2 would be the excessreagent
Do You Understand Limiting Reagents?In one process, 124 g of Al are reacted with 601 g of Fe2O32Al + Fe2O3 Al2O3 + 2FeCalc...
Use limiting reagent (Al) to calculate amount of product thatcan be formed.g Al mol Al mol Al2O3 g Al2O3124 g Al1 mol Al27...
Theoretical Yield• The theoretical yield is the amount of productthat can be made– In other words it’s the amount of produ...
Percent YieldA comparison of the amount actually obtainedto the amount it was possible to makeActual YieldTheoretical Yiel...
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Chem 101 week 5

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Chem 101 week 5

  1. 1. CHEM 101PowerpointsWeek Ending 2/17/2012Chapter 3Part 2
  2. 2. 3.6g CO2 mol CO2 mol C g Cg H2O mol H2O mol H g Hg of O = g of sample – (g of C + g of H)Combust 11.5 g ethanolCollect 22.0 g CO2 and 13.5 g H2O6.0 g C = 0.5 mol C1.5 g H = 1.5 mol H4.0 g O = 0.25 mol OEmpirical formula C0.5H1.5O0.25Divide by smallest subscript (0.25)Empirical formula C2H6O
  3. 3. A process in which one or more substances ischanged into one or more new substances is achemical reactionA chemical equation uses chemical symbols to show what happens during a chemicalreaction
  4. 4. Anatomy of a Chemical EquationCH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)
  5. 5. Anatomy of a Chemical EquationReactants appear on the leftside of the equation.CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)
  6. 6. Anatomy of a Chemical EquationProducts appear on the rightside of the equation.CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)
  7. 7. Anatomy of a Chemical EquationThe states of the reactants and products arewritten in parentheses to the right of eachcompound.CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)
  8. 8. Anatomy of a Chemical EquationCoefficients are inserted tobalance the equation.CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)
  9. 9. Subscripts and Coefficients GiveDifferent Information• Subscripts tell the number of atoms ofeach element in a molecule
  10. 10. Subscripts and Coefficients GiveDifferent Information• Subscripts tell the number of atoms ofeach element in a molecule• Coefficients tell the number of molecules
  11. 11. 3.73 ways of representing the reaction of H2 with O2 to form H2Oreactants productsSummary of a Chemical Equation
  12. 12. How to “Read” Chemical Equations2 Mg + O2 2 MgO2 atoms Mg + 1 molecule O2 makes 2 formula units MgO2 moles Mg + 1 mole O2 makes 2 moles MgO48.6 grams Mg + 32.0 grams O2 makes 80.6 g MgOIS NOT2 grams Mg + 1 gram O2 makes 2 g MgO3.7
  13. 13. Balancing Chemical Equations1. Write the correct formula(s) for the reactants on theleft side and the correct formula(s) for the product(s)on the right side of the equation.Ethane reacts with oxygen to form carbon dioxide and waterC2H6 + O2 CO2 + H2O2. Change the numbers in front of the formulas(coefficients) to make the number of atoms of eachelement the same on both sides of the equation. Donot change the subscripts.3.72C2H6 NOT C4H12
  14. 14. Balancing Chemical Equations3. Start by balancing those elements that appear in onlyone reactant and one product.C2H6 + O2 CO2 + H2O3.7start with C or H but not O2 carbonon left1 carbonon rightmultiply CO2 by 2C2H6 + O2 2CO2 + H2O6 hydrogenon left2 hydrogenon right multiply H2O by 3C2H6 + O2 2CO2 + 3H2O
  15. 15. Balancing Chemical Equations4. Balance those elements that appear in two or morereactants or products.3.72 oxygenon left4 oxygen(2x2)C2H6 + O2 2CO2 + 3H2O+ 3 oxygen(3x1)multiply O2 by72= 7 oxygenon rightC2H6 + O2 2CO2 + 3H2O72remove fractionmultiply both sides by 22C2H6 + 7O2 4CO2 + 6H2O
  16. 16. Balancing Chemical Equations5. Check to make sure that you have the same number ofeach type of atom on both sides of the equation.3.72C2H6 + 7O2 4CO2 + 6H2OReactants Products4 C12 H14 O4 C12 H14 O4 C (2 x 2) 4 C12 H (2 x 6) 12 H (6 x 2)14 O (7 x 2) 14 O (4 x 2 + 6)
  17. 17. © 2009, Prentice-Hall, Inc.Stoichiometric CalculationsThe coefficients in the balanced equation give theratio of moles of reactants and products.
  18. 18. © 2009, Prentice-Hall, Inc.Stoichiometric CalculationsStarting with the massof Substance A youcan use the ratio ofthe coefficients of Aand B to calculate themass of Substance Bformed (if it’s aproduct) or used (ifit’s a reactant).
  19. 19. 1. Write balanced chemical equation2. Convert quantities of known substances into moles3. Use coefficients in balanced equation to calculate the number of moles of thesought quantity4. Convert moles of sought quantity into desired unitsAmounts of Reactants and Products3.8
  20. 20. Methanol burns in air according to the equation2CH3OH + 3O2 2CO2 + 4H2OIf 209 g of methanol are used up in the combustion,what mass of water is produced?grams CH3OH moles CH3OH moles H2O grams H2Omolar massCH3OHcoefficientschemical equationmolar massH2O209 g CH3OH1 mol CH3OH32.0 g CH3OHx4 mol H2O2 mol CH3OHx18.0 g H2O1 mol H2Ox =235 g H2O3.8
  21. 21. LimitingReactants
  22. 22. How Many Cookies Can I Make?• You can make cookiesuntil you run out of oneof the ingredients• Once this family runs outof sugar, they will stopmaking cookies……• ………..at least anycookies you would wantto eat!
  23. 23. How Many Cookies Can I Make?• In this example the sugarwould be the limitingreactant, because it willlimit the amount ofcookies you can make
  24. 24. Limiting ReactantsThe limiting reactant isthe reactant present inthe smalleststoichiometric amount
  25. 25. Limiting Reactants• The limiting reactant is the reactant present in thesmallest stoichiometric amount– In other words, it’s the reactant you’ll run out of first (inthis case, the H2)
  26. 26. Limiting ReactantsIn the example below, the O2 would be the excessreagent
  27. 27. Do You Understand Limiting Reagents?In one process, 124 g of Al are reacted with 601 g of Fe2O32Al + Fe2O3 Al2O3 + 2FeCalculate the mass of Al2O3 formed.g Al mol Al mol Fe2O3 needed g Fe2O3 neededORg Fe2O3 mol Fe2O3 mol Al needed g Al needed124 g Al1 mol Al27.0 g Alx1 mol Fe2O32 mol Alx160. g Fe2O31 mol Fe2O3x = 367 g Fe2O3Start with 124 g Al need 367 g Fe2O3Have more Fe2O3 (601 g) so Al is limiting reagent3.9
  28. 28. Use limiting reagent (Al) to calculate amount of product thatcan be formed.g Al mol Al mol Al2O3 g Al2O3124 g Al1 mol Al27.0 g Alx1 mol Al2O32 mol Alx102. g Al2O31 mol Al2O3x = 234 g Al2O32Al + Fe2O3 Al2O3 + 2Fe3.9
  29. 29. Theoretical Yield• The theoretical yield is the amount of productthat can be made– In other words it’s the amount of product possibleas calculated through the stoichiometry problem• This is different from the actual yield, theamount one actually produces and measures
  30. 30. Percent YieldA comparison of the amount actually obtainedto the amount it was possible to makeActual YieldTheoretical YieldPercent Yield = x 100

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