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					   Limiting Reagents

This program will help you better
   understand stoichiometry
problems with a limiting reagent.
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.
  Use factor label.
           Limiting Reagent
• Which of the ingredients will run out first?

• Sam has:
  – 50 slices of bologna
  – 64 slices of cheese
  – 60 buns
• 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 Br2     1 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.
0.25moles Br2     1 mole SrBr2   0.25moles SrBr2
                   1 mole Br2

0.25moles SrBr2     247.4g 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.
Is that your final answer?

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