Ethanol (C2H6O) undergoes a combustion reaction with oxygen gas to form two products, one of which is water. How many mL of ethanol would be needed to produce 0.0034 L of H2O?

Answer 1

Write the correctly balanced chemical equation:

C2H6O +3O2 ==> 2CO2 + 3H2O

To answer the question about how many ml of ethanol are needed to produce 0.0034 L (3.4 ml) of water, we either need additional information (such as densities, pressure, temperature, etc), or we can make certain assumptions. If we assume a density of H2O of 1.0 g/ml, then we can find moles of H2O produced.

3.4 ml H2O x 1 g/ml x 1 mole/18 g = 0.189 moles H2O

From the balanced equation, we can find moles C2H6O needed:

moles C2H6O = 0.189 moles H2O x 1 mole C2H6O/3 moles H2O = 0.063 moles C2H6O needed

mass of C2H6O needed = 0.063 moles x 46.07 g/mole = 2.90 g

If we assume a density of 0.789 g/ml for ethanol, then 2.90 g x 1 ml/0.789 g = 3.68 mls C2H6O needed

If all reactants and products are in the gas phase, we need to know the temperature and the pressure under which the reaction takes place. Then one can use the ideal gas law, PV = nRT to find moles of water, moles of ethanol and volume of ethanol.