Question

Hess's law states that "the heat released or absorbed in a chemical process is the same whether the process takes place in one or in several steps."

It is important to recall the following rules:

When two reactions are added, their enthalpy values are added.

When a reaction is reversed, the sign of its enthalpy value changes.

When the coefficients of a reaction are multiplied by a factor, the enthalpy value is multiplied by that same factor.

Part A

Calculate the enthalpy of the reaction

2NO(g)+O2(g)→2NO2(g)

given the following reactions and enthalpies of formation:

12N2(g)+O2(g)→NO2(g),   ΔH∘A=33.2 kJ

12N2(g)+12O2(g)→NO(g),  ΔH∘B=90.2 kJ

Express your answer with the appropriate units.

View Available Hint(s)

ΔH∘ =

nothingnothing

Submit

Part B

Calculate the enthalpy of the reaction

4B(s)+3O2(g)→2B2O3(s)

given the following pertinent information:

B2O3(s)+3H2O(g)→3O2(g)+B2H6(g),    ΔH∘A=+2035 kJ

2B(s)+3H2(g)→B2H6(g),                            ΔH∘B=+36 kJ

H2(g)+12O2(g)→H2O(l),                ΔH∘C=−285 kJ

H2O(l)→H2O(g),                                          ΔH∘D=+44 kJ

Express your answer with the appropriate units.

View Available Hint(s)

ΔH∘ =

nothingnothing

Submit

Answer 1