When glucose undergoes fermentation, ethanol and carbon dioxide are formed. #"C"_6"H"_12"O"_6 -> 2"C"_2"H"_5"OH" + 2"CO"_2#. Calculate the mass of ethanol that could be obtained from 25 g of glucose?

1 Answer
Truong-Son N.
Jan 25, 2018

This is just asking for a theoretical yield, i.e. what could you make if the reaction had complete conversion of glucose to products.

You'd get #"13 g"# of ethanol... more exactly, #"12.79 g"#, but you only gave two sig figs.

The reaction coefficients can be related by the unit of mols, which you get from the molar mass.

#25 cancel("g C"_6"H"_12"O"_6) xx ("1 mol glucose")/(180.156 cancel"g glucose") = "0.1388 mols glucose"#

If you had #"1 mol"# of glucose, you would get #"2 mols ethanol"#. So since you have #"0.1388 mols"# of glucose, you get #"0.2775 mols ethanol"#.

#0.1388 cancel"mols glucose" xx ("2 mols ethanol")/(cancel"1 mol glucose") = "0.2775 mols ethanol"#

And this many mols has a mass of...

#0.2775 cancel("mols CH"_3"CH"_2"OH") xx ("46.07 g")/cancel("1 mol EtOH")#

#=# #color(blue)"13 g ethanol"#

to two sig figs.

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