Question

given the following data:
enthalpy of formation for various
nitrogen oxide compounds
using hesss law, the enthalpy of reaction for the following equation: n₂o(g) + no₂(g) → 3no(g) is calculated to be
record your 3 - digit answer. include sign in the first box only; do not include units in second box.

Explanation:

Step1: Write the enthalpy of formation values

Given: $\Delta H_f(N_2O)=81.7\ kJ/mol$, $\Delta H_f(NO_2)=33.2\ kJ/mol$, $\Delta H_f(NO)=91.3\ kJ/mol$

Step2: Apply Hess's Law formula

Hess's Law formula for $\Delta H_{rxn}=\sum n\Delta H_f(products)-\sum m\Delta H_f(reactants)$
For the reaction $N_2O(g)+NO_2(g)\to3NO(g)$
$\Delta H_{rxn}=[3\times\Delta H_f(NO)]-[\Delta H_f(N_2O)+\Delta H_f(NO_2)]$
Substitute the values:
$\Delta H_{rxn}=(3\times91.3)-(81.7 + 33.2)$
$=273.9-(114.9)$
$=159$

Answer:

159