On the basis of your experience, predict which of the...

On the basis of your experience, predict which of the following reactions are spontaneous. (a) $\mathrm{Zn}(s)+2 \mathrm{H}^{+}(a q) \longrightarrow \mathrm{Zn}^{2+}(a q)+\mathrm{H}_{2}(g)$ (b) $\mathrm{CaCO}_{3}(s)+2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{Ca}(\mathrm{OH})_{2}(s)+\mathrm{H}_{2} \mathrm{CO}_{3}(a q)$ (c) $\mathrm{CH}_{4}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(g)$ (d) $\mathrm{Ag}^{+}(a q)+\mathrm{Cl}^{-}(a q) \longrightarrow \mathrm{AgCl}(s)$

On the basis of your experience, predict which of the following reactions are spontaneous.
(a) $\mathrm{Zn}(s)+2 \mathrm{H}^{+}(a q) \longrightarrow \mathrm{Zn}^{2+}(a q)+\mathrm{H}_{2}(g)$
(b) $\mathrm{CaCO}_{3}(s)+2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{Ca}(\mathrm{OH})_{2}(s)+\mathrm{H}_{2} \mathrm{CO}_{3}(a q)$
(c) $\mathrm{CH}_{4}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(g)$
(d) $\mathrm{Ag}^{+}(a q)+\mathrm{Cl}^{-}(a q) \longrightarrow \mathrm{AgCl}(s)$

Key Concepts

Spontaneity and Gibbs Free Energy

This concept refers to the tendency of a chemical reaction to occur without external intervention. It is determined by the Gibbs free energy change (?G), where a negative value indicates a spontaneous process. ?G depends on both the enthalpy change (?H) and the entropy change (?S) of the reaction, making it a fundamental tool in predicting reaction behavior under given conditions.

Redox Reactions

Redox reactions involve the transfer of electrons between chemical species, resulting in changes in the oxidation states of the elements involved. Predicting the spontaneity of these reactions often uses the standard electrode potentials, which indicate the tendency of a species to be oxidized or reduced. This is crucial for understanding and forecasting how such reactions proceed.

Precipitation Reactions

Precipitation reactions occur when ions in solution combine to form an insoluble solid, known as the precipitate. The formation of the precipitate is driven by the reduction in free energy as the solute species exit the solution, with the solubility product (Ksp) playing a key role in determining the conditions under which the reaction is spontaneous.

Combustion Reactions

Combustion reactions are highly exothermic processes that typically involve a fuel reacting with oxygen to produce heat, light, and combustion products like CO2 and H2O. The significant release of energy and the increase in overall entropy often drive these reactions to be spontaneous under appropriate conditions.

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