Lec28-Chap-4-3

# Lec28-Chap-4-3 - Reactions with Reactant in Limited Supply...

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39 Reactions with Reactant in Limited Supply Given 10 slices of cheese and 14 slices of bread. How many sandwiches can you make? Balanced equation 1 cheese + 2 bread 1 sandwich 1 cheese 2 bread 1 cheese 1 sandwich 2 bread 1 sandwich 40 Two methods can be used. Both treat as a unit conversion problem Product Method Product Method Calculate the product from each starting material. ± The reactant giving the smallest smallest number is limiting. 10 cheese x = 10 sandwiches 1 sandwich 1 cheese 14 bread x = 7 sandwiches 1 sandwich 2 bread Correct answer Bread is limiting. It will be used up first Reactions with Limited Reactants

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43 How much water will be produced by the combustion of 25.0 g of H 2 in the presence of 100. g of O 2 ? Write a balanced equation: n H2 = 25.0 g = 12.40 mol H 2 1 mol H 2 2.016 g 2 H 2 (g) + O 2 (g) 2 H 2 O( l ) n O2 = 100. g = 3.125 mol O 2 1 mol O 2 32.00 g Reactions with Limited Reactants 44 2 H 2 + O 2 2 H 2 O Moles available: 12.40 3.125 Using H 2 12.40 mol H 2 (2H 2 O /2H 2 ) = 12.40 mol H 2 O Using O 2 3.125 mol O 2 (2 H 2 O/1 O 2 ) = 6.250 mol H 2 O O 2 gave less water. O 2 is limiting is limiting . Base all calculations on O 2 6.250 mol H 2 O x (18.02 g/ 1 mol ) = 113. g water 113. g water How much water will be produced? Product Method Reactions with Limited Reactants

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45 2 H 2 + O 2 2 H 2 O Moles available: 12.40 3.125 e.g. choose H 2 O 2 needed: 12.40 mol H 2 (1 O 2 /2 H 2 )= 6.20 mol Not available …. O 2 is limiting is limiting . You only need one calculation.
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Lec28-Chap-4-3 - Reactions with Reactant in Limited Supply...

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