Ethanol, C2H5OH burns with oxygen in air to give carbon dioxide and water. What is the amount (in moles) of water produced from 0.51 mol C2H5OH? The equation is C2H5OH + 3O2 -----> 2CO2 + 3H2O.

Quick answer:

The amount of water produced from 0.51 moles C2H5OH is 1.53 moles of water.

Expert Answers

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This is an example of a combustion reaction.  To answer this you must first balance the equation.

The easiest way is to set up the reaction equation without any coefficients:

C2H6O + O2 -->  CO2  + HOH

Now start balancing, first with carbon, then with hydrogen and last the oxygen.

There are 2 carbons on the left  and 6 hydrogens so you add a coefficient of 2 in front of the CO2 and a 3 in front of the water.

C2H6O  +  O2 -->  2 CO2  +  3 HOH

Now count the number of oxygen on the product side and you get seven.  One oxygen came from the ethanol so you need 6 more from oxygen. Add a coefficient of 3 in front of the oxygen on the reactant side and your reaction is balanced.

C2H60  + 3 O2  -->  2 CO2  +  3 HOH

This shows you that for every mole of ethanol, you will get 3 moles of water.  So if you start with 0.51 moles of ethanol, you will produce 3 x .51 or 1.53 moles of water.

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