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Thursday, Oct. 14th: A Day Agenda

Finiosh Lab: ?Stoichiometry and Gravimetric Analysis". Get your beaker, paper towel, filter paper and dried precipitate out of the drying oven (is should be cool already) and record the mass (

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Thursday, Oct. 14th: A Day Agenda

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    2. Thursday, Oct. 14th: “A” Day Agenda Finish 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: Ch. 9 vocabulary crossword puzzle Chapter 9 Test/Concept Review: Wednesday, Oct. 20th Reminder: Late concept reviews WILL NOT be accepted!

    3. Finiosh Lab: “Stoichiometry and Gravimetric Analysis” Get your beaker, paper towel, filter paper and dried precipitate out of the drying oven (is should be cool already) and record the mass (#5). 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)

    4. Finish Lab: “Stoichiometry and Gravimetric Analysis” Examining Data Calculate the mass of the dry precipitate 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 formed.

    5. Finish Lab: “Stoichiometry and Gravimetric Analysis” Examining Data Use the mole ratio from your balanced equation in question #1 to convert from moles of SrCO3 to moles of Na2CO3.

    6. Finish Lab: “Stoichiometry and Gravimetric Analysis” 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 drum if we had excess Na2CO3 left over after the reaction.

    7. Finish Lab: “Stoichiometry and Gravimetric Analysis” 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.

    8. Finish Lab: “Stoichiometry and Gravimetric Analysis” Applying Conclusions Start with the #moles of Na2CO3 calculated from question #2 and use the molar mass of Na2CO3 to calculate the number of grams of Na2CO3 that were in the 15 mL sample.

    9. Finish Lab: “Stoichiometry and Gravimetric Analysis” Applying Conclusions How many grams of Na2CO3 are present in the 575 L drum? Hint: you know how many grams of Na2CO3 were in a 15 mL sample from question #6.

    10. Finish Lab: “Stoichiometry and Gravimetric Analysis” 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 to question #6 as the actual yield and calculate the percentage error: Actual yield X 100% Theoretical Yield

    11. Finish Lab: “Stoichiometry and Gravimetric Analysis” Designing Experiments What possible sources of error can you identify with your procedure? Could have done multiple trials Precipitate wasn’t washed thoroughly Precipitate wasn’t dried thoroughly Could have put dried precipitate back in beaker, washed with distilled water, and re-filtered Errors in mass measurements

    12. Finish Lab: “Stoichiometry and Gravimetric Analysis” Make sure your table of contents is updated and put your lab folders in the bin.

    13. In-Class Assignment Chapter 9 review, pg. 329-331: #1-8, 13-15, 21a, 24a, 27b, 29b, 31, 34, 37 If you get this done, work on the concept review. Chapter 9 Test/Concept Review: Wednesday, Oct. 20th

    14. Extra Credit Opportunity Go to the fall play this Thursday OR Saturday night at 7:30 p.m. in the auditorium. Find me during intermission and get me to sign your program. Bring your signed program next class and I’ll give you 10 points extra credit towards the 1st quarter!

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