Thursday, Feb. 6 th : “A” Day Friday, Feb. 7 th : “AB” Day Agenda  Collect Homework: “Chemistry Gas Law Practice” worksheet  Check lab write-ups  Lab discussion: “Stoichiometry: Mass-Volume”  Lab: “Stoichiometry: Mass-Volume”  Completed lab will be due next time…

Lab:“Stoichiometry: Mass-Volume” Discussion 1.Refer to the diagram in your handout for proper equipment set-up. 2.You don’t have to get exactly 4.00 g of lead carbonate – just be sure to record the actual mass that you used. 3.The procedure doesn’t specifically tell you to record data in the data table – but be sure to do so before moving on to the next step.

Lab: “Stoichiometry: Mass-Volume” Discussion 3.Make sure the Pb compound is spread out in the bottom half of the test tube and that the test tube is clamped at an angle. 4.In step #4, be sure to REMOVE THE DELIVERY TUBE AT THE SAME TIME YOU STOP HEATING the test tube. WHY? 5.Remember, you are collecting gaseous CO 2 by water displacement. It’s the volume of GAS that you’re interested in, NOT the volume of water.

Lab: “Stoichiometry: Mass-Volume” Safety Items 1.Avoid contact with lead compounds. Inhalation of dust/fumes can be harmful. Rinse spills with plenty of water. 2.Tie back hair when using bunsen burners. 3.Test tube will be hot – be careful! 4.Put the Pb compound in the waste container when you’re done.

Lab: “Stoichiometry: Mass-Volume” Analysis Section 2.To determine the theoretical volume of CO 2 produced at STP, start with the mass of lead carbonate you used and use stoichiometry to find moles of CO 2.  3.96 g Pb carb X 1 mol Pb carb = mol Pb 775 g Pb carb carb  mol Pb carb X 2 mol CO 2 =.0102 mol CO 2 1 mol Pb carb

Lab: “Stoichiometry: Mass-Volume” Analysis Section  Avogadro’s theory states that 1 mole of ANY gas at STP has a volume of 22.4 L.  Use Avogadro’s theory to change moles of CO 2 to liters of CO 2 (at STP). .0102 mol CO 2 X 22.4 L CO 2 = L CO 2 STP) 1 mol CO 2  Change to mL: L CO 2 X 1,000 mL = 228 mL 1 L CO 2 (theoretical volume of CO STP)

Lab: “Stoichiometry: Mass-Volume” Analysis Section 3. To determine the volume of dry gas collected at STP, we first need to adjust atmospheric pressure to account for the gas being collected through water… P 1 = Atmospheric pressure (kPa) – vapor pressure of water (kPa) at T 1 (pg 835 in book) kPa kPa = kPa (adjusted pressure)

 Now, use the combined gas law and solve for V 2 at STP: P 1 V 1 = P 2 V 2 T 1 T 2  “1” is your data and “2” are STP conditions.  P 1 = adjusted pressure; V 1 = volume of gas you collected; T 1 = your temperature (K)  Solve for V 2 (Actual volume of CO 2 produced at STP) Lab: “Stoichiometry: Mass-Volume” Analysis Section

Lab: “Stoichiometry: Mass-Volume” Conclusion Questions  Remember: All conclusion questions and your reflection statement need to be answered using COMPLETE SENTENCES! Conclusion Question Hints… 1.PbO is a solid. Remember, the gas was collected through water. 2.Use stoichiometry and the balanced equation.

Lab: “Stoichiometry: Mass-Volume” Analysis Section 3.Experimental error = (V 2 ) theoretical vol at STP – actual vol at STP X 100% theoretical vol at STP 4.Remember, the gas was collected through water… 5.Add conclusion question #5 to your lab: What type of reaction was this?

“Stoichiometry: Mass-Volume”  Be sure to update your table of contents.  When finished, put your lab back in your folder and put it in the bin to be graded…  That’s it, you’re done!