1. Grab… handouts on door calculator from front desk 2. Begin the Do Now Do Now Use your notes to help you! 1.When converting from moles to mass, what do you multiply the number of moles with? 2.When converting from mass to moles, what do you divide the mass by? 3.What are the units for molar mass? Stoichiometry - Mass to Moles: moles x molar mass - Moles to Mass: mass ÷ molar mass - Moles of X to Moles of Y: moles x mole ratio Pre-Lab Practice: Moles Mass 1. How many grams are in 2 moles of H2O? 2. How many grams are in 3 moles of CH4? 3. How many grams are in 5 moles of HF? Aspirin Lab How do you compare bottled water to water from EPIC’s water fountains? How can we determine what’s good and what’s bad? Lab Question Are brand name commercial prescription drugs better than homemade prescription drugs? While you wait… Start you lab report using your Lab Report Format sheet…. -Purpose: What are we determining and how? -Hypothesis: Which do you believe is more pure and why? Theoretical Yield C7H6O3(s) + C4H6O3(aq) C9H8O4(s) + C2H4O2(aq) How much did we start with? Molar Masses? Mole Ratio? Lets climb up & down the mole hill… Percent Yield & Percent Error Percent Yield: How much product you obtained Percent yield = (actual yield ÷ theoretical yield) x 100% Percent Error: How accurate you were Percent error = | actual yield – theoretical yield | x 100 % theoretical yield Conclusion Restate the purpose Explain your hypothesis (accepted or rejected?) Results – use your results to answer the purpose! Unknown – what were some unexpected errors that occurred? If your percent yield was not 100%, then why? New – what can you change if you were to perform this lab again? Climbing the Mole Hill Let’s Put it all together: 2H2O2(aq) 2H2O(l) + O2(g) 1. If you start with 6 grams of H2O2, how many grams of O2 will you produce? 2. If you produce 36 grams of H2O, how many grams of H2O2 did you start with?