How do you balance C_2H_5OH(l) + O_2(g) -> CO_2(g) + H_2O(g)C2H5OH(l)+O2(g)CO2(g)+H2O(g) and determine the mass of CO_2CO2 produced from the combustion of 100.0 g ethanol?

1 Answer
Jul 10, 2018

C_2H_5OH +2O_2 -> 2CO_2 + 3H_2OC2H5OH+2O22CO2+3H2O

mass of CO_2CO2 = 191 g

Explanation:

Part 1: Balancing equation:

C_2H_5OH + O_2 -> CO_2 + H_2OC2H5OH+O2CO2+H2O

We'll do that by counting the number of atoms on the left and right hand side of the equation and get them to be the same.

L-- Atom--R
2 -- C -- 1
6 -- H -- 2
3 -- O -- 3

Looks like C and H are not balanced. Since there are 2 C on the left and only 1 C on the right, we'll add 2 in front of CO_2CO2 on the right.

C_2H_5OH + O_2 ->color(red) 2CO_2 + H_2OC2H5OH+O22CO2+H2O

Updating the atom counts on the right:
L-- Atom--R
2 -- C -- color(red)cancel(1)2
6 -- H -- 2
3 -- O -- color(red)cancel(3)5

Now that C is balanced, we'll move on to H. There are 6 H on the left and only 2 H on the right, we'll add 3 in front of H_2O on the right.

C_2H_5OH + O_2 -> 2CO_2 + color(red)3H_2O

Updating the atom counts on the right:
L-- Atom--R
2 -- C -- cancel(1)2
6 -- H -- color(red)cancel(2)6
3 -- O -- cancel(3)5

All that's left now is to balance O. We have 3 O on the left and 5 O on the right. If we add a 2 in front of O_2 on the left, we'll balance O:

C_2H_5OH + color(red)2O_2 -> 2CO_2 + 3H_2O

Updating the atom counts on the right:
L-- Atom--R
2 -- C -- cancel(1)2
6 -- H -- cancel(2)6
5color(red)cancel(3)-- O -- cancel(3)5

Part 2: Find mass CO_2 from mass ethanol, C_2H_5OH

The plan is to perform the following 3 steps calculations starting from "mass " C_2H_5OH to "mass "CO_2

"mass " C_2H_5OH ->" moles " C_2H_5OH -> " moles " CO_2 -> "mass "CO_2

  • Converting mole to mole will require the stoichiometric coefficient (numbers in front of balanced equation).
  • Converting from mass to mole of the same substance will require its molar mass.

In that case, we'll need to find the molar mass of

  • C_2H_5OH=2(12)+5(1)+16+1= 46 g/"mol"

  • CO_2=12+2(16)= 44 g/"mol"

Calculations can be set up this way. Notice how the units cancel each other out leaving "g "CO_2:
"mass of "CO_2=100" g " C_2H_5OH*(1" mol "C_2H_5OH)/(46" g " C_2H_5OH)*(2" mol "CO_2)/(1" mol "C_2H_5OH)*(44" g "CO_2)/(1" mol "CO_2)=191" g " CO_2