1 LIMITING REACTANT Unit 8 Lesson 2 Limiting
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1 LIMITING REACTANT Unit 8 Lesson 2
Limiting Reactants 2 Limiting Reactant - reactant you run out of first Reactant in Excess - reactant you have more than enough of To determine the limiting reactant, find the number of moles of each reactant and then divide by their respective coefficients
Example Problem 3 What is the limiting reactant if you have 5. 0 g H 2 and 10. 0 g O 2? 2 H 2 + O 2 → 2 H 2 O Meaning for every 2 moles of H 2 you need 1 mole of O 2 5. 0 g H 2 (1 mole H 2/2. 016 g H 2) = 2. 5 moles of H 2 10. 0 g O 2(1 mole O 2 /32. 00 g O 2) = 0. 313 moles O 2
4 Continued: divide each by their coefficients O 2 has the smaller value, so oxygen must be the limiting reactant
Example Problem 5 Identify the limiting reactant and the mass of sodium chloride produced when 1. 7 g of sodium reacts with 2. 6 L of chlorine gas at STP. 2 Na + Cl 2 2 Na. Cl To identify the limiting reactant: 1. 7 g Na x 1 mol Na/22. 99 g Na = 0. 074 mol Na Divide by Na coefficient: 0. 074 mol Na/2 mol = 0. 037 2. 6 L Cl 2 x 1 mol Cl 2/22. 4 L Cl 2 = 0. 12 mol Cl 2 Divide by Cl 2 coefficient: 0. 12 mol Cl 2/1 mol = 0. 12
6 Na is limiting because less Na. Cl could be made from 1. 7 g of Na (0. 037) than 2. 6 L Cl 2 (0. 12) To determine Na. Cl produced: go back to mol Na and complete stoichiometry 0. 074 mol Na x (2 mol Na. Cl/2 mol Na) x 58. 44 g Na. Cl/mol. Na. Cl = 4. 3 g Na. Cl
Sample Problem 7 When 22. 6 g of barium and 4. 2 g of nitrogen gas react, which is the limiting reactant and how many grams of barium nitride are produced? 3 Ba + N 2 Ba 3 N 2 Barium is limiting reactant 24. 2 g Ba 3 N 2
