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Stoichiometry

This laboratory exercise covers stoichiometry calculations involving reactants and products quantities, along with percentage yield calculations and a heating curve lab experiment for understanding phase changes of water.

johncovington
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Stoichiometry

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  1. Stoichiometry Warm-up 5/2/11 H2(g) + O2(g) H2O(g) How many moles of oxygen are needed to react with 3.7 moles hydrogen gas? How many moles of water can be produced from 12.5 g of oxygen? How many grams of hydrogen are needed to produce 67.0 grams of water?

  2. Percent Yield 5/2/11 Actual yield X 100 theoretical yield

  3. Percent Yield 5/2/11 What is the percent yield if 13.1 g CaO is actually and the theoretical yield is 15.2 g? 13.1 X 100 = 15.2 86.2 %

  4. Percent Yield 5/2/11 If 50.0 g of silicon dioxide is heated with excess of carbon, 27.9 g of silicon carbide is produced. SiO2 (s)+ 3C (s) SiC (s) + 2CO(g) What is the percent yield?

  5. Percent Yield 5/2/11 If 15.0 g of nitrogen reacts 15.0 g of hydrogen, 10.5 g of ammonia is produced. N2 (g)+ H2(g) NH3(g) What is the percent yield in this reaction?

  6. The Heat is on 5/4/11 warm-up Let’s finish test if not What are the 3 equations you need for heat? Look in chapter 17 What temperature does water freeze and ice melt? What temperature does water boil and steam condense?

  7. Critical point – temp and pressure that distinction between gas and liquid stops • Critical point for water 374.4 oC at 217.7 atm • Critical point for CO2 31 oC at 73 atm

  8. Heating curve lab • Procedure: • With a partner scoop out enough ice to fill your beaker • Get a thermometer • Place thermometer in ice without it touching bottom of beaker, may have to use paperclip to balance on side • Make sure hot plate is on, do not touch. • Record initial temperature and every minute throughout the trial until water boils for 5 minutes. • Graph data with Temp on Y-axis and time on X

  9. Heating curve lab write up • Your lab report sheet should include: • The purpose of the lab • A complete heating curve for your groups data • Construct a cooling curve of your data (#2 &3 on graph paper) • Draw the molecules at each of the different intervals of the process from solid to vapor. See pg 41 • Explain what heat energy was doing at interval of no temp change. • Why is it important to constantly stir the water during the lab? • When was our system in physical equilibria throughout the lab?

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