Monday, May 6 th : “A” Day Tuesday, May 7 th : “B” Day Agenda  Homework Questions/Collect: Pg. 248: #1-7  Sec. 7.3 quiz  Lab write-up: “Quantitative Determination of an Empirical Formula”  Homework: “More Practice…” worksheet We will be in the lab next time Please dress appropriately No Flip-Flops!

Homework Questions/Problems  Sec. 7.3 review, pg. 248: #1-7

 You may use your notes, your book, a periodic table, a calculator, your brain, and your 2:00 partner’s brain to complete the quiz… Good Luck! Section 7.3 quiz

Lab Partners

Lab Discussion “Quantitative Determination of an Empirical Formula”  Remember, the empirical formula is the simplest whole-number ratio of elements in a chemical compound.  For example, the ratio of hydrogen atoms to oxygen atoms in H 2 O is always 2:1, not 2.5:1 or 1.75:1

“Quantitative Determination of an Empirical Formula” Purpose  In this lab, you will React a carefully determined amount of tin, Sn, with excess nitric acid, HNO 3, to form a tin-oxygen crystalline product. Calculate the mole ratio of tin and oxygen in the crystalline product. Predict an empirical formula for the tin-oxygen product.

“Quantitative Determination of an Empirical Formula” Material Changes  Changes: Cross out the hot plate. We will be using a bunsen burner set-up, NOT a hot plate. Change forceps to crucible tongs.

 Additions: 20 mesh granulated tin (Sn) 8M nitric acid (HNO 3 ) 10 mL graduated cylinder Beaker tongs “Quantitative Determination of an Empirical Formula” Additions

“Quantitative Determination of an Empirical Formula” Procedure Changes  Step #1: Make sure to prepare a data table as instructed BEFORE the lab.  Cross out step #2: you will be using a bunsen burner, NOT a hot plate.  Step #3 Addition: After heating/cooling evaporating dish/watch glass cover, measure mass to nearest 0.01g/record in data table!  Step #4: change 30 mesh granulated tin to 20 mesh granulated tin.

 Step #5 Addition: Record 3 observations when the nitric acid, HNO 3, was added to the tin, Sn.  Step #6 Addition: Record 2 observations when heating dish over the water bath.  Step #8 Addition: Record 2 observations when heating dish over hot flame. “Quantitative Determination of an Empirical Formula” Procedure Changes

Data Table  You will need to construct a date table as directed in step #1 in the “Analysis” section. You need to do this BEFORE lab day – I will be checking to make sure you have a table.  Also, you will need to record the following observations: Step #5: 3 observations Step #6: 2 observations Step #7: 2 observations  These observations are worth 7 pts!

“Quantitative Determination of an Empirical Formula” Lab Write-Up  Title  Purpose  Hypothesis: What do you think the empirical formula for the tin-oxygen product will be?  Materials  Procedure tin and oxygen

Homework  “More Practice with % Composition and Empirical Formulas” worksheet  For up to 4 points extra credit: NAME the 4 compounds in each of the problems on the worksheet