1. Stoichiometry: Limiting Reagents and Percent Yield
SCH 3U/4C

2. Review
In a chemical reaction, how do we relate moles of one compound to moles of another?
What are the four steps to go from mass of one reactant or product to the mass of another?
2A + B
A2B
MOLE RATIO!

3. Review Mass to Mass Steps: 1. Write the balanced equation
2. Convert mass of given to moles
3. Use the mole ratio from the balanced equation to find moles of the unknown
4. Convert moles of the unknown to mass of the unknown

4. Salad Chemistry Remember our salad analogy….
What if we had 3 heads of lettuce, four cucumbers, and 15 radishes? Would we still make 3 full salads?

5. Limiting Reagents
Reactants are rarely present in amounts that correspond exactly to the mole ratios in the balanced equation
Limiting reactant: a reactant that is completely consumed during a chemical reaction and limits the amount of product that can be formed
Excess reactant: a reactant that remains after a reaction is over
In our salad example, the four cucumbers limits the number of salads we can make, while the lettuce and radishes would be in excess..

6. Mole Ratios

7. Stiochiometry Judges!
In pairs, you will have 1 minute to answer each of the following questions
When you have the answer write it on your paper and hold it up (like a skating judge).
If you got it right, award your team a point!
Ready? Set? GO!

8. How many molecules of NaCl are needed to react with one molecule of sulfuric acid?
How many molecules of NaCl are needed to react with 3 dozen molecules of sulfuric acid?
How many molecules of sodium sulfate are formed from 2 molecules of NaCl?
How many molecules of HCl are formed from 4 molecules of sulfuric acid?

9. How many molecules of NaCl are needed to make 6 million molecules of sodium sulfate?
How many moles of NaCl form 1 mole of sodium sulfate?
How many moles of HCl will be formed from 1 mole of sulfuric acid?
How many moles of HCl are formed from 0.5 molecules of sulfuric acid?
How many moles of sulfuric acid are needed to form 0.5 mole of sodium sulfate?

10. Homework Question 2 of “Introduction to Stiochiometry Probems”
Practice Problems