Limiting Reactant Videodisk 4 Unit 8 Lesson 3 (Honors)

Limiting Reactants 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 Paperclip Demo Envelopes of paperclips Give students the formula of the molecule and have them build as many as possible of that molecule. Discuss the limiting reactant and the reactant in excess.

Example Problem What is the limiting reactant if you have 5.0g H2 and 10.0g O2? 2H2 + O2 → 2H2O Meaning for every 2 moles of H2 you need 1 mole of O2 5.0g H2 (1 mol H2 2.016g H2 10.0 g O2(1mol O2 32.00g O2 = 2.5 mol of H2 = 0.303 mol of O2

Continued: divide each by their coefficients O2 has the smaller value, so oxygen must be the limiting reactant

Example Problem 2Na + Cl2  2NaCl 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. 2Na + Cl2  2NaCl To identify the limiting reactant:

Na is limiting because less NaCl could be made from 1. 7 g of Na (0 Na is limiting because less NaCl could be made from 1.7 g of Na (0.037) than 2.6 L Cl2 (0.12) To determine NaCl produced: go back to mol Na and complete stoichiometry = 4.3 g NaCl

Barium is limiting reactant Sample Problem What mass of barium nitride (Ba3N2) is produced from the reaction between 22.6 g barium and 4.2 g nitrogen gas? What is the limiting reactant? 3Ba + N2  Ba3N2 Barium is limiting reactant 24.1 g Ba3N2