In honor of Homecoming, two special cartoons…

Thursday, Oct. 10th: “A” Day (GO BEARS!)Friday, Oct. 11th: “B” Day

AgendaFinish Lab: “Stoichiometry and Gravimetric

Analysis”In-Class Assignment:

Chapter 9 review, pg. 329-331: #1-8, 13-15, 21a, 24a, 27b, 29b, 31, 34, 37

Homework: Concept Review

Chapter 9 Test/Concept Review due:Thursday 10-17/Friday, 10-18

Reminder: Late concept reviews WILL NOT be accepted!

Finish Lab: “Stoichiometry and Gravimetric Analysis”Get your beaker, paper towel, filter paper and

dried precipitate out of the drying oven and record the total mass (#5).

1.Organizing Data Write a balanced equation for the reaction.

Na2CO3 (aq) + SrCl2 (aq) → 2 NaCl (aq) + SrCO3 (s)

What kind of reaction was this?Double Displacement

What is the precipitate?SrCO3 (strontium carbonate)

Finish Lab: “Stoichiometry and Gravimetric Analysis”

2. Examining DataCalculate the mass of the dry precipitate

(#6) by subtracting the mass of the filter paper (#3) and the mass of the beaker with paper towel (#4) from the total mass of beaker, paper towel, filter paper, and dried precipitate (#5).

Record the mass of the dry precipitate in table. (#6)

Use the molar mass of SrCO3 to calculate the number of moles of precipitate formed.

Finish Lab: “Stoichiometry and Gravimetric Analysis”

3. Examining Data Use the mole ratio from the balanced

equation in question #1 to change moles SrCO3 moles Na2CO3.

Finish Lab: “Stoichiometry and Gravimetric Analysis”

4. Evaluating Methods Calculate the #moles of SrCl2 that were added if

there was 0.30 mol SrCl2 in every liter of solution.

Was SrCl2 or Na2CO3 the limiting reactant?Na2CO3

Would this experiment have worked if SrCl2 was the limiting reactant?

No, we wouldn’t be able to determine how much Na2CO3 was in the vat if we had

excess Na2CO3 left over after the reaction.

Finish Lab: “Stoichiometry and Gravimetric Analysis”

5. Evaluating Methods Why was the SrCO3 rinsed in step 11?

To remove any impurities. What soluble impurities could have been on

the filter paper along with the precipitate? NaCl

How would the results vary if the precipitate had not been completely dry?

The mass would have been greater due to the mass of the water.

Finish Lab: “Stoichiometry and Gravimetric Analysis”

6. Applying Conclusions Start with the #moles of Na2CO3 from

question #3 and use the molar mass of Na2CO3 to change

moles Na2CO3 grams Na2CO3

Finish Lab: “Stoichiometry and Gravimetric Analysis”

7. Applying Conclusions How many grams of Na2CO3 are present in

the 575 L drum? Hint: you just calculated how many grams

of Na2CO3 were in the 15 mL sample. Use that information as a conversion factor.

Finish Lab: “Stoichiometry and Gravimetric Analysis”

8. Evaluating Methods We used a 0.5M solution, which means that

there was 0.795 g Na2CO3 for every 15 mL (this is the theoretical yield)

Use your answer from question #6 as the actual yield and calculate the percentage yield:

Actual yield X 100% Theoretical Yield

Finish Lab: “Stoichiometry and Gravimetric Analysis”

Don’t forget your reflection statement:Was your hypothesis correct?What were some sources of error in the lab?How could you minimize these sources of errors in future trials?Did this lab help you to understand how stoichiometry could be used outside of the lab?Your reflection statement should be a paragraph

with complete sentences!

Finish Lab: “Stoichiometry and Gravimetric Analysis”

Make sure your table of contents is updated and put your lab folders back in the bin to be graded.

In-Class Assignment/Homework

Chapter 9 review, pg. 329-331: #1-8, 13-15, 21a, 24a, 27b, 29b, 31, 34, 37

Next time: Jeopardy reviewChapter 9 Test/Concept Review

due:Thursday, Oct. 17th

Friday, Oct. 18th