Enthalpy Practice Test - MCAT Physical

The formation of nitrous oxide is a 2-step process.

$N_{2} + O_{2} \rightarrow 2NO (step 1)$

$2NO + O_{2} \rightarrow 2NO_{2} (step 2)$

$N_{2} + 2O_{2} \rightarrow 2NO_{2} (overall reaction)$

The overall enthalpy of the reaction is +68kJ.

If the enthalpy change of step 1 is 180kJ, what is the enthalpy change of step 2?

Consider the following processes:

$A \rightarrow 2B + C + \Delta H_{1}$

$D\rightarrow B + C + \Delta H_{2}$

$D \rightarrow 2E + \Delta H_{3}$

Which for the following expresses $\Delta H$ for the process $A + C \rightarrow 4E$ ?