# For each of the following reactions, use the values listed in Appendix IIB calculate \Delta H ...

## Question:

For each of the following reactions, use the values listed in Appendix IIB calculate {eq}\Delta H rxn, \Delta S rxn and \Delta G rxn at 25 ^{\circ} C {/eq} and state whether the process is spontaneous or non-spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous? If so, should the temperature be raised or lowered from {eq}25 ^{\circ} C {/eq}?

a) CaCO3 (s) CaO (s) + CO2 (g)

spontaneity:

b) N2 (g) + O2 (g) 2 NO (g)

spontaneity:

c) 2 NH3 (g) N2H4 (g) + H2 (g)

## Gibb's Free Energy

Gibb's free energy of a reaction ({eq}\Delta G_{rxn} {/eq}) can be calculated many different ways. Under standard conditions, many of the Gibb's free energy of chemicals are tabulated and can be calculated directly. However, if the enthalpy and entropy of the reaction are known, Gibb's free energy of the reaction can be calculated by

$$\Delta G_{rxn} = \Delta H_{rxn} - T \Delta S_{rxn}$$

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The enthalpy and entropy of reaction are calculated from the tabulated values of the reactants and products, by subtracting the values of the...

Spontaneous Reactions & Gibbs Free Energy

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Chapter 12 / Lesson 8
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In this lesson, we will learn about spontaneous reactions and how we can use Gibbs free energy to predict them. We will remind ourselves about enthalpy and entropy and discuss the importance of temperature and spontaneity.