How do you write an equation to represent "Azomethane (#C_2H_6N_2#) decomposes to form ethane (#C_2H_6#) and nitrogen gas"?

1 Answer
Apr 18, 2016


#"C"_ 2"H"_ 6"N"_ (2(g)) -> "C"_ 2"H"_ (6(g)) + "N"_(2(g))#


All you have to do here is make sure that the chemical equation that describes this decomposition reaction obeys the Law of mass conservation.

Azomethane, #"C"_2"H"_6"N"_2#, is said to decompose to form ethane, #"C"_2"H"_6#, and nitrogen gas. Let's assume for a second that you don't know the chemical formula of nitrogen gas.

You could write the chemical equation as

#"C"_ 2"H"_ 6"N"_ (2(g)) -> "C"_ 2"H"_(6(g)) + "nitrogen gas"#

Now, the Law of mass conservation states that all the atoms present on the reactants' side must also be present on the products' side.

Since matter cannot be created or destroyed in a chemical reaction, you know for a fact that each atom that took part in the reaction must now be a part of the products.

The reactants' side, which contains azomethane, will have

  • two atoms of carbon, #2 xx "C"#
  • six atoms of hydrogen, #6 xx "H"#
  • two atoms of nitrogen, #2 xx "N"#

This is exactly how many atoms you must end up with once the reaction is finished. As you can see, the reactants' side already contains

  • two atoms of carbon, #2 xx "C"#
  • six atoms of hydrogen, #6 xx "H"#

This means that nitrogen gas must contain #2# atoms of nitrogen, since you know that two atoms of nitrogen are needed to balance out what's on the reactants' side.

Since you're dealing with gaseous compounds, the chemical formula for nitrogen gas will be #"N"_2#, i.e. the two nitrogen atoms will be bonded together.

Therefore, the chemical reaction that describes this decomposition reaction will look like this

#color(green)(|bar(ul(color(white)(a/a)color(black)("C"_ 2"H"_ 6"N"_ (2(g)) -> "C"_ 2"H"_ (6(g)) + "N"_(2(g)))color(white)(a/a)|)))#