One way to measure the \"greenness\" of a reaction is to calculate atom economy.

Question

One way to measure the "greenness" of a reaction is to calculate atom economy. Atom economy = (grams desired product / grams or all products and byproducts) Times 100 The combustion of ethanol can be used to fuel a car. Write a balanced chemical equation for the combustion of ethanol. Be sure to specify the phases for each compound. What is the Delta Hrxn in kJ? Calculate the atom economy for the reaction using the following scenarios. CO2 is considered the desired product H2O is considered the desired product Both CO2 and H2O are considered waste. Which number most accurately reports atom economy for the reaction? Explain your reasoning.

Explanation / Answer

Chemical equation - 1)C2H5OH (l) + 3 O2 (g) ? 2 CO2 (g) + 3 H2O (g) 2)?Hrxn = -1371 kJ/mol 3a) ans = (grams of CO2 )/(grams ofC2H5OH + grams of O2 + grams of CO2 + grams of H2O)*100 = 2*44*100/(46 + 32 + 2*44 + 3*18) = 40% b)ans = (grams of H2O )/(grams ofC2H5OH + grams of O2 + grams of CO2 + grams of H2O)*100 = 3*18*100/(46 + 32 + 2*44 + 3*18)= 24.54 % c) ans= (grams of CO2 + grams of H20)/(grams ofC2H5OH + grams of O2 + grams of CO2 + grams of H2O)*100 = (2*44 + 3*18)*100/(46 + 32 + 2*44 + 3*18) = 64.54 % d) The number which represents the most accurate atomic efficiency is the one which is calculated with the most desired product. So if the desired oproduct is CO2 then the first number represents it accurately. if its H2O then thesecond and if both are the desired products then the last number accurately represents the atomic efficiency . Please rate

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