Chapter 5, Problem 5.28NP

Interpretation Introduction

Interpretation:

The entropy changes; ΔS, ΔS_surr and ΔS_universe at T = 298 K for the following reaction needs to be calculated

  $2\text{ 2Glycine(s) }\to {\text{ Glycylglycine(s) + H}}_{\text{2}}\text{O(l)}$

Concept Introduction:

The standard enthalpy change for a reaction ${\text{ΔH}}_{\text{R}}^{\text{0}}$ measured at 298 K and 1 atm is given in terms of the difference in the standard enthalpy of formation of the products and that of reactants.

  ${\text{ΔH}}_{\text{R}}^{\text{0}}\text{ = }{\displaystyle \sum {\text{n}}_{\text{p}}{\text{ΔH}}_{\text{f}}^{\text{0}}}\text{(products) - }{\displaystyle \sum {\text{n}}_{\text{r}}{\text{ΔH}}_{\text{f}}^{\text{0}}}\text{(reactants) ------(1)}$

Here,

n_p and n_r are the number of moles of the products and reactants

The standard entropy change for a reaction ${\text{ΔS}}_{\text{R}}^{\text{0}}$ measured at 298 K and 1 atm is given in terms of the difference in the standard entropy of formation of the products and that of reactants.

  ${\text{ΔS}}_{\text{R}}^{\text{0}}\text{ = }{\displaystyle \sum {\text{n}}_{\text{p}}{\text{S}}_{\text{f}}^{\text{0}}}\text{(products) - }{\displaystyle \sum {\text{n}}_{\text{r}}{\text{S}}_{\text{f}}^{\text{0}}}\text{(reactants) ------(2)}$

The entropy change of the universe is the sum of the entropy changes of the system and surroundings

  ${\text{ΔS}}_{\text{universe}}{\text{= ΔS}}_{\text{system}}{\text{+ ΔS}}_{\text{surr}}\text{ ------(3)}$