Use the data from Table 6.2 to calculate ΔH^∘ for the following reactions. On the basis of their

step 1 We really can't determine whether or not a reaction is spontaneous solely with the delta H value

Use the data from Table 6.2 to calculate ΔH^∘ for the...

Use the data from Table 6.2 to calculate $\Delta H^{\circ}$ for the following reactions. On the basis of their values of $\Delta H^{\circ},$ which are favored to occur spontaneously? (a) $\mathrm{CaO}(s)+\mathrm{CO}_{2}(g) \longrightarrow \mathrm{CaCO}_{3}(s)$ (b) $\mathrm{C}_{2} \mathrm{H}_{2}(g)+2 \mathrm{H}_{2}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g)$ (c) $3 \mathrm{CaO}(s)+2 \mathrm{Fe}(s) \longrightarrow 3 \mathrm{Ca}(s)+\mathrm{Fe}_{2} \mathrm{O}_{3}(s)$

Use the data from Table 6.2 to calculate $\Delta H^{\circ}$ for the following reactions. On the basis of their values of $\Delta H^{\circ},$ which are favored to occur spontaneously?
(a) $\mathrm{CaO}(s)+\mathrm{CO}_{2}(g) \longrightarrow \mathrm{CaCO}_{3}(s)$
(b) $\mathrm{C}_{2} \mathrm{H}_{2}(g)+2 \mathrm{H}_{2}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g)$
(c) $3 \mathrm{CaO}(s)+2 \mathrm{Fe}(s) \longrightarrow 3 \mathrm{Ca}(s)+\mathrm{Fe}_{2} \mathrm{O}_{3}(s)$

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Key Concepts

Reaction Enthalpy Calculation

This is the process of determining the enthalpy change of a chemical reaction by subtracting the sum of the standard enthalpies of formation of the reactants from that of the products. It is essential for assessing the energy profile of reactions.

Spontaneity and Exothermic Reactions

The energetics of a reaction, particularly whether it is exothermic (releases heat) or endothermic (absorbs heat), can provide insights into its tendency to occur spontaneously under standard conditions, although full spontaneity assessment also requires consideration of entropy and temperature effects.

Standard Enthalpy of Formation

This concept refers to the enthalpy change when one mole of a compound forms from its elements in their standard states. It serves as the fundamental basis for calculating reaction enthalpies, using tabulated values for individual substances, such as those provided in data tables like Table 6.2.

Hess's Law

Hess's Law is the principle that the total enthalpy change for a reaction is the same regardless of the pathway taken. It allows for the calculation of unknown reaction enthalpies by combining formation reactions, utilizing the additive properties of enthalpy changes.

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