Chapter 9valverdescience.pbworks.com/w/file/fetch/63874502/9...• suppose that 6.7 mol Na react...
Transcript of Chapter 9valverdescience.pbworks.com/w/file/fetch/63874502/9...• suppose that 6.7 mol Na react...
9.2 Chemical Calcualtions
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Chapter 9Stoichiometry
9.1 The Arithmetic of Equations
9.2 Chemical Calculations
9.3 Limiting Reagent and Percent Yield
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9.3 Limiting Reagent and Percent Yield
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objectivesIdentify and use limiting reagent in a reaction to calculate the maximum amount of products produced and the amount of excess reagent.Calculate theoretical yield, actual yield, or percent yield given appropriate information.,
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vocabularylimiting reagent excess reagenttheoretical yield
actual yield
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1.If a carpenter had two table table tops and seven table legs. He would have difficulty building more than one functional table.
2.A similar concept applies in chemistry when knowing the exact amounts of reactants and products in a chemical reaction.
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Yirah Valverde, M. Ed.
limiting reagent• the amount of product is determined by the limiting reagent.
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sample 9.8• sodium chloride can be prepared by the
reaction of sodium metal with chlorine gas.
• suppose that 6.7 mol Na react with 3.20 mol Cl2
• what is the limiting reagent?• how many moles of NaCl are produced?
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9.8 sample
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known:moles of sodium=6.70 Namoles of chlorine= 3.20 Cl22 mo of Na= 1 mol Cl2
unknown:limiting reagent=?
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9.8 sample
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•This calculation indicates that 3.35mol Cl2 is needed to react with 6.70 mol Na
•Only 3.20 mol of Cl2 is available, Cl becomes the limiting reagent.
•Sodium is in excess.
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knownsamount of limiting reagent= 3.2 mol Cl21 mol Cl2= 2 mol NaCl
unknownsmoles of sodium chloride= ? mol NaCl
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9.8 sample
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knowns• amount of limiting
reagent=3.20 mol Cl2• 1mol Cl2 = 2 mol NaCl (from
balanced equation)
unknowns• moles of sodium chloride= ?
mol NaCl
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9.8 sample
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knowns• amount of limiting
reagent=3.20 mol Cl2• 1mol Cl2 = 2 mol NaCl (from
balanced equation)
unknowns• moles of sodium chloride= ?
mol NaCl
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Yirah Valverde, M. Ed.
9.8 sample• solve for the unknown
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Yirah Valverde, M. Ed.
9.8 sample• suppose that 6.7 mol Na react with 3.20 mol Cl2• solve for the unknown
• This calculation indicates that 3.35mol Cl2 is needed to react with 6.70 mol Na
• Only 3.20 mol of Cl2 is available, Cl becomes the limiting reagent. • Sodium is in excess.
• Do these results make sense?
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Yirah Valverde, M. Ed.
9.8 sampleDo these results make sense?
• the ratio of the given moles of sodium chloride to chlorine was greater than 2:1, which is the ratio from the balanced equation, sodium should be in excess and chlorine should be the limiting reagent.
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9.9 sample
• The properties of copper (I) sulfide are very different from the properties of the elements copper and sulfur.
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copper sulfate copper sulfur
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9.9 sample
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What is the limiting reagent when 80 g Cu reacts with 25 g S?What is the maximum number of grams of that can be formed?
knownmass of copper 80g Cumass of Sulfur 25g S2 mol Cu= 1 mol S (from balanced equation)
unknownlimiting reagent
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9.9 sample
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What is the limiting reagent when 80 g Cu reacts with 25 g S?What is the maximum number of grams of that can be formed?
limiting reagent
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9.9 sample
• Comparing the amount of sulfur needed (.630mol S) with the given amount (.779 mol S) indicated that sulfur is in excess. Thus copper is the limiting reagent.
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What is the limiting reagent when 80 g Cu reacts with 25 g S?What is the maximum number of grams of that can be formed?
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9.9 sample
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knownlimiting reagent=1.26 mol Cu2 mol Cu=1 mol
1 mol = 159.1 g
unknownmass of
What is the limiting reagent when 80 g Cu reacts with 25 g S?What is the maximum number of grams of that can be formed?
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Yirah Valverde, M. Ed.
9.9 sample
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the limiting reagent, which was determined in the last step is used to calculate the max amount of Cu2 formed
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9.9 sample
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the limiting reagent, which was determined in the last step is used to calculate the max amount of Cu2 formed
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homework problems
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a) identify the limiting reagentb) calculate the number of moles and grams of water produced
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homework problems
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• Theoretical Yield:–the maximum amount of product that can be formed
from the given reactants–obtained by calculations
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• Actual Yield:–The amount of product that actually forms in the
laboratory.–The actual yield is often less than the theoretical
yield.
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• Percent Yield:–the ratio of the actual yield to the theoretical yield
expressed as a percent.
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9.10 sample
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Calcium carbonate is decomposed by heating as shown in the equation....
1. what is the theoretical yield of CaO is 24.8g of CaCO3 is heated?2. what is the percent yield if 13.1g CaCO is produced?
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9.10 sample
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Calcium carbonate is decomposed by heating as shown in the equation....
1. what is the theoretical yield of CaO is 24.8g of CaCO3 is heated?2. what is the percent yield if 13.1g CaO is produced? ACTUAL WHEN IS PRODUCED
knowns1 mol CaCO3=1mol CaO (balanced equation)1mol CaCO3= 100.1 g CaCO3 (mass)1 mol CaO=56.1 g CaO (molar mass)
unknownstheoretical yield of calcium oxide=?
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9.10 sample
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knownsactual yield= 13.1 CaOtheoretical yield= 13.9 g CaO (from the first calculation)
unknownspercent yield ?
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9.10 sample
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