Limiting Reagents This program will help you better understand stoichiometry problems with a limiting reagent.
Simulation Sam works at the Salem Sandwich Shoppe. Sam expected a big day on Tuesday, so he ordered the following: 5 pounds of bologna (10 slices per pound) 4 pounds of cheese (16 slices per pound) 5 packages of buns (12 buns per package) How many sandwiches can Sam make?
How Many? • First, let’s look at how Sam will assemble each sandwich: 1 slice bologna + 1 slice cheese on 1 bun • Now we need to determine how many slices of bologna, how many slices of cheese and how many buns did Sam buy.
Limiting Reagent • Which of the ingredients will run out first? • Sam has: • 50 slices of bologna • 64 slices of cheese • 60 buns
CORRECT • You got it right, the bologna is going to run out first because there are only 50 slices. • Therefore we can deduce that Sam can only make 50 sandwiches. • Sam will have excess cheese and buns.
Simulation Conclusion • Even though Sam started with 5 pounds of bologna and only 4 pounds of cheese; he ran out of bologna first. • Why? It matter how many slices, not the mass of the material when determining which ingredient runs out first. • Now let’s relate this concept to chemistry and stoichiometry.
Problem #1 • How many grams of product can you produce if you react 26.28g of strontium with 39.95g of bromine. • Write a balanced equation. • Convert both masses to moles.
Sr + Br2 SrBr2 26.28g Sr 1 mole Sr 0.30 moles Sr 87.6g Sr 39.95g Br21 mole Br2 0.25 moles Br2 159.8g Br2 Which reactant is the limiting reagent?
Br2 is the limiting reagent! The Br2 will run out first because there are less moles of Br2 than Sr. Now calculate the mass of product using the number of moles of the limiting reagent.
STOICHIOMETRY BABY 0.25moles Br21 mole SrBr2 0.25moles SrBr2 1 mole Br2 0.25moles SrBr2247.4g SrBr2 61.85g SrBr2 1 mole SrBr2
Problem #2 How many grams of sodium chloride will be produced if 0.93g of sodium oxide reacts with 1.67g of barium chloride? Write a balanced equation. Convert both grams to moles. Determine the limiting reagent. Use the limiting reagent calculate the mass of NaCl. Show your work on your paper and then click for the answer.