How many moles of oxygen must be used for the complete combustion of 203.383 moles of ethanol (C2H5OH)?

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The first step to solving this problem is to write and balance the equation. When a hydrocarbon combusts completely with oxygen, the products are carbon dioxide and water:

`C_2H_5OH + 3 O_2 -gt 2 CO_2 + 3 H_2O`

The coeffcients used to balance a chemical equation represent the moles of the substances. Since oxygen has a coefficient of 3 and ethanol has a coefficient of 1, we know that three moles of O2 are required for every mole of ethanol that reacts, or we can say that the mole ratio of O2 to C2H5OH is 3:1. To find the number of moles of oxygen, multiply the given number of moles of ethanol by this mole ratio:

203.383 moles C2H5OH x (3 moles O2)/(1 mole C2H5OH) = 610.149 moles O2

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