Determine whether the reactions listed below are...

Determine whether the reactions listed below are entropy-favored or disfavored under standard conditions. Predict how an increase in temperature will affect the value of $\Delta_{\tau} G^{\circ}$ (a) $\mathrm{I}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{I}(\mathrm{g})$ (b) $2 \mathrm{SO}_{2}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{SO}_{3}(\mathrm{g})$ (c) $\mathrm{SiCl}_{4}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(\ell) \rightarrow \mathrm{SiO}_{2}(\mathrm{s})+4 \mathrm{HCl}(\mathrm{g})$ (d) $\mathrm{P}_{4}(\mathrm{s}, \text { white })+6 \mathrm{H}_{2}(\mathrm{g}) \rightarrow 4 \mathrm{PH}_{3}(\mathrm{g})$

Determine whether the reactions listed below are entropy-favored or disfavored under standard conditions. Predict how an increase in temperature will affect the value of $\Delta_{\tau} G^{\circ}$
(a) $\mathrm{I}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{I}(\mathrm{g})$
(b) $2 \mathrm{SO}_{2}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{SO}_{3}(\mathrm{g})$
(c) $\mathrm{SiCl}_{4}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(\ell) \rightarrow \mathrm{SiO}_{2}(\mathrm{s})+4 \mathrm{HCl}(\mathrm{g})$
(d) $\mathrm{P}_{4}(\mathrm{s}, \text { white })+6 \mathrm{H}_{2}(\mathrm{g}) \rightarrow 4 \mathrm{PH}_{3}(\mathrm{g})$

Key Concepts

Gibbs Free Energy

Gibbs free energy (?G) is a thermodynamic potential that indicates the spontaneity of a process at constant pressure and temperature. It is defined by the equation ?G = ?H - T?S, where ?H represents the enthalpy change and ?S the entropy change. A negative ?G suggests a favored reaction under given conditions, while a positive ?G implies that the reaction is non-spontaneous.

Entropy

Entropy (S) is a measure of the disorder or randomness in a system. In reactions, changes in the number of gas molecules, phase changes, or dissociation processes can significantly influence the entropy. An increase in the number of gaseous species or a transition from a more ordered to a less ordered state generally leads to an increase in entropy, which can drive a reaction towards spontaneity.

Temperature Effect on Reaction Spontaneity

Temperature plays a critical role in the value of ?G due to the T?S term in the free energy equation. For reactions with a positive ?S (entropy favored), an increase in temperature will make ?G even more negative, potentially favoring the reaction further. Conversely, if ?S is negative (entropy disfavored), higher temperatures can result in more positive ?G values, making the reaction less spontaneous.

Standard Conditions in Thermodynamics

Standard conditions provide a baseline for comparing thermodynamic data, typically set at 1 atm pressure and 298 K temperature (25°C). This framework allows chemists to calculate and compare values for ?H, ?S, and ?G across reactions, and to predict the effect of changing conditions such as temperature on the spontaneity of reactions.

Transcript

Please give Ace some feedback