
Kevin T. answered 05/20/21
UCLA Grad Looking to Teach Biology
Rearrange each individual chemical equation so that in the end, when you add up the equations, you end up with the desired equation: 2CO + 2NO --> 2CO2 + N2
Equation 1: 2CO + O2 --> 2CO2
Equation 2: N2 + O2 --> 2NO
In the final equation, there is no O2, so you flip the Equation 2 to cancel out the O2.
2CO + O2 --> 2CO2
2NO --> N2 + O2
--------------------------
2CO + 2NO --> 2CO2 + N2
Whenever you flip an equation, you flip the sign of its enthalpy value. So, delta H for Equation 2 would change from 180.6 to -180.6 kJ
Then, just add up the new enthalpy values: -566 + (-180) = -746.6 kJ