Use Table 16.1 to calculate ΔS^∘ for each of the following reactions. (a) 2 Cl^-(a q)+I2(s) ⟶Cl2

step 1 So the standard entropy change can be calculated using the following equation. Delta S -naut is

Use Table 16.1 to calculate ΔS^∘ for each of the following...

Use Table 16.1 to calculate $\Delta S^{\circ}$ for each of the following reactions. (a) $2 \mathrm{Cl}^{-}(a q)+\mathrm{I}_{2}(s) \longrightarrow \mathrm{Cl}_{2}(g)+2 \mathrm{I}^{-}(a q)$ (b) $\mathrm{SO}_{4}^{2-}(a q)+4 \mathrm{H}^{+}(a q)+\mathrm{Cd}(s) \longrightarrow$ $$\begin{array}{l}\mathrm{Cd}^{2+}(a q)+\mathrm{SO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l) \\\text { (c) } 2\mathrm{Br}^{-}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{Br}_{2}(l)+\mathrm{H}_{2}(g)+2\mathrm{OH}^{-}(a q)\end{array}$$

Use Table 16.1 to calculate $\Delta S^{\circ}$ for each of the following reactions.
(a) $2 \mathrm{Cl}^{-}(a q)+\mathrm{I}_{2}(s) \longrightarrow \mathrm{Cl}_{2}(g)+2 \mathrm{I}^{-}(a q)$
(b) $\mathrm{SO}_{4}^{2-}(a q)+4 \mathrm{H}^{+}(a q)+\mathrm{Cd}(s) \longrightarrow$
$$\begin{array}{l}\mathrm{Cd}^{2+}(a q)+\mathrm{SO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l) \\\text { (c) } 2\mathrm{Br}^{-}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{Br}_{2}(l)+\mathrm{H}_{2}(g)+2\mathrm{OH}^{-}(a q)\end{array}$$

Key Concepts

Standard Entropy

Standard entropy refers to the absolute entropy value of a substance at a specified temperature (commonly 298 K) and pressure (typically 1 atm), as measured under standard conditions. These values, given in units such as joules per mole per Kelvin (J/mol·K), represent the degree of randomness or disorder present in the substance and are tabulated in thermodynamic data tables.

Standard Reaction Entropy Change

The standard reaction entropy change, ?S°, is calculated by taking the difference between the sum of the standard molar entropies of the products and that of the reactants, each multiplied by their respective stoichiometric coefficients. This concept is crucial for understanding the direction and feasibility of chemical reactions in terms of disorder and energy dispersion.

Thermodynamic Data Tables

Thermodynamic data tables, like the referenced Table 16.1, provide standard-state values such as enthalpy, entropy, and Gibbs free energy for various substances. These tables are essential tools in physical chemistry for performing accurate thermodynamic calculations including the determination of ?S° for chemical reactions.

Standard States

The concept of standard states refers to the set of conditions (typically 1 atm pressure and 298 K temperature) under which thermodynamic properties are measured and tabulated. Understanding standard states is necessary to ensure consistency when applying data from thermodynamic tables to calculate reaction entropy changes.

Stoichiometry in Thermodynamic Calculations

Stoichiometry plays a vital role in thermodynamic calculations where each chemical species’ contribution to the overall entropy change is weighted according to its coefficient in the balanced chemical equation. This systematic approach ensures that the calculated entropy change accurately reflects the proportions of substances involved in the reaction.

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