Name Gas Unit Activity Gas Stoichiometry The purpose of this learning activity is four fold I Review and apply some basic chemical skills reaction stoichiometry II Practice problem solving in a small group III Make a new chemistry friend IV Learn how this class functions 1 Watch a short video clip When posed the question Where does most of the mass that makes up a tree come from originally What did the people in the video say If you d like to watch the whole video or other parts http www learner org vod vod window hteml pid 77 From the ground from water from the ground from nutrients in the soil Roughly 60 of the mass of a tree comes from cellulose Cellulose shown to the right is a polymer very large molecule composed of repeating units made from 1000 s of glucose monomers per cellulose molecule 2 The formula of the monomer unit glucose is C6H12O6 Look at the condensed structural formula of cellulose and try to circle one monomer unit See picture Trees make their own glucose via photosynthesis The glucose is used for energy to drive the biochemistry of the trees It is stored as starch It is also used for the structure of the tree trunk branches leaves etc and is linked together to form cellulose 3 During photosynthesis what compounds combine in the presence of sunlight to make glucose Water H2O and Carbon Dioxide CO2 4 Write the balanced chemical equation for the formation of glucose in the presence of sunlight Revised SH 6 17 13 LaBrake Vanden Bout 2013 Name 6CO2 6H2O C6H12O6 6O2 5 Based on this balanced chemical equation where does most of the mass of the tree come from Choose from the following a b c d nutrients in the ground water from the ground carbon dioxide from the air sunlight from the Sun 6 Assuming that 60 of the mass of a tree comes from cellulose and knowing that cellulose is made of glucose monomers and knowing the balanced equation for the production of glucose answer the following Using your stoichiometry skills determine the mass of carbon dioxide needed to make a 300 lb oak tree What mass of carbon dioxide is needed to make a 300 lb tree 1 lb 454 g a not enough information was given impossible to answer b 44 lbs c 184 lbs d 264 lbs Assuming 60 of the mass of the tree is cellulose 180 lbs of tree is from glucose which comes from CO2 Assume that the CO2 is chemically modified to become glucose via the photosynthesis reaction Reaction Equation 6CO2 6H2O C6H12O6 6O2 Given 180 lbs C6H12O6 Wanted lbs CO2 Conversion Path lbs C6H12O6 g C6H12O6 mol C6H12O6 mol CO2 g CO2 lbs CO2 Conversion factors 1 lb 454 g 180 g C6H12O6 1 mole C6H12O6 6 mole CO2 1 mole C6H12O6 44 g CO2 1 mole CO2 180 lbs C6H12O6 454 g C6H12O6 1 lb C6H12O6 1 mol C6H12O6 180 g C6H12O6 6 mole CO2 1 mole C6H12O6 44 g CO2 1 mole CO2 1 lb CO2 454 g CO2 264 lbs CO2 When you hear of people speaking of their carbon footprint they are talking about how much carbon they put in the environment not how much carbon dioxide they put in the environment Revised SH 6 17 13 LaBrake Vanden Bout 2013 Name 7 Carry this problem one step further and report how many lbs of carbon are taken from the air to form the 300 lb tree What mass of carbon is needed to make the 300 lb tree Assume that all the carbon in the tree comes from the carbon dioxide from the atmosphere a It is not possible to answer this question given this information b 27 lbs c 72 lbs d 180 lbs To answer this question just use the formula stoichiometry to get the mass of C in CO2 by dividing the molar mass of C by the molar mass of CO2 12gC 44gCO2 0 2727 or about 27 So about 27 of the mass of the compound comes from C Thus 27 times the mass of carbon dioxide CO2 will be the mass of carbon 0 27 264lbs 72 lbs Revised SH 6 17 13 LaBrake Vanden Bout 2013
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