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Chapter 16: Q16.5 CYL (page 895)

Calculate the standard entropy change for the following process:

\({{\bf{H}}_{\bf{2}}}{\bf{(g) + }}{{\bf{C}}_{\bf{2}}}{{\bf{H}}_{\bf{4}}}{\bf{(g)}} \to {{\bf{C}}_{\bf{2}}}{{\bf{H}}_{\bf{6}}}{\bf{(g)}}\)

Short Answer

Expert verified

The standard entropy change for above process is \( - 120.66\;{\rm{J}}/{\rm{Kmol}}\)

Step by step solution

01

Define enthalpy of the reaction

  • Enthalpy change is defined as the difference in enthalpies of all the product and the reactants each multiplied with their respective number of moles. It is represented as
  • The equation used to calculate enthalpy change is of a reaction is:
  • \(\Delta {H_{rxn}} = \sum {\left[ {n \times \Delta {H_{f({\rm{ product }})}}} \right]} - \sum {\left[ {n \times \Delta {H_{f({\rm{ reactant }})}}} \right]} \)
02

Determine the enthalpy of the reaction.

\({{\rm{H}}_{2(\;{\rm{g}})}} + {{\rm{C}}_2}{{\rm{H}}_{4(\;{\rm{g}})}} \cdots {{\rm{C}}_2}{{\rm{H}}_{6(\;{\rm{g}})}}\)

\(\Delta {S_{{\rm{rxn }}}} = \Delta {S_{{\rm{Product }}}} - \Delta {S_{{\rm{Reactant }}}}\)

\(\Delta {\rm{S}}\)of \({{\rm{H}}_{2(\;{\rm{g}})}} = 130.7\;{\rm{J}}/{\rm{K}} \cdot \) mole

\(\Delta S\)of \({{\rm{C}}_2}{{\rm{H}}_{4(\;{\rm{g}})}} = 219.56\;{\rm{J}}/{\rm{K}} \cdot \) mole

\(\Delta {\rm{S}}\)of \({{\rm{C}}_2}{{\rm{H}}_{6(\;{\rm{g}})}} = 229.6\;{\rm{J}}/{\rm{K}} \cdot \) mole

\(\Delta {S_{{\rm{rxn }}}} = \Delta {S_{{\rm{Product }}}} - \Delta {S_{{\rm{Reactant }}}}\)

\( = \left\{ 1 \right.\)mole \( \times \Delta S\) of \(\left. {{C_2}{H_{6(g)}}} \right\} - \left\{ 1 \right.\) mole \( \times \Delta S\) of \({H_{2(g)}} + 1\) mole \( \times \Delta S\) of \(\left. {{C_2}{H_{4(g)}}} \right\}\)

\( = \{ 229.6\;{\rm{J}}/{\rm{K}}\} - \{ 130.7\;{\rm{J}}/{\rm{K}} + 219.56\;{\rm{J}}/{\rm{K}}\} \)

\( = - 120.66\;{\rm{J}}/{\rm{K}}\)

\(\Delta {S_{{\rm{rxn}}}} = - 120.66\;{\rm{J}}/{\rm{K}}\)

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Most popular questions from this chapter

What happens to \({\bf{\Delta G}}_{{\bf{298}}}^{\bf{^\circ }}\) (becomes more negative or more positive) for the following chemical reactions when the partial pressure of oxygen is increased?

(a) \({\bf{S(s) + }}{{\bf{O}}_{\bf{2}}}{\bf{(g)}} \to {\bf{S}}{{\bf{O}}_{\bf{2}}}{\bf{(g)}}\)

(b) \({\bf{2S}}{{\bf{O}}_{\bf{2}}}{\bf{(g) + }}{{\bf{O}}_{\bf{2}}}{\bf{(g)}} \to {\bf{S}}{{\bf{O}}_{\bf{3}}}{\bf{(g)}}\)

(c) \({\bf{HgO(s)}} \to {\bf{Hg(l) + }}{{\bf{O}}_{\bf{2}}}{\bf{(g)}}\)

Many plastic materials are organic polymers that contain carbon and hydrogen. The oxidation of these plastics in air to form carbon dioxide and water is a spontaneous process; however, plastic materials tend to persist in the environment. Explain.

Use the thermodynamic data provided in Appendix G to calculate the equilibrium constant for the dissociation of dinitrogen tetraoxide at 25 °C.

Describe how matter and/or energy is redistributed when you empty a canister of compressed air into a room.

Without doing a numerical calculation, determine which of the following will reduce the free energy change for the reaction, that is, make it less positive or more negative, when the temperature is increased. Explain.

(a) \({{\bf{N}}_{\bf{2}}}{\bf{(g) + 3}}{{\bf{H}}_{\bf{2}}}{\bf{(g)}} \to {\bf{2N}}{{\bf{H}}_{\bf{3}}}{\bf{(g)}}\)

(b) \({\bf{HCl(g) + N}}{{\bf{H}}_{\bf{3}}}{\bf{(g)}} \to {\bf{N}}{{\bf{H}}_{\bf{4}}}{\bf{Cl(s)}}\)

(c) \({\left( {{\bf{N}}{{\bf{H}}_{\bf{4}}}} \right)_{\bf{2}}}{\bf{C}}{{\bf{r}}_{\bf{2}}}{{\bf{O}}_{\bf{7}}}{\bf{(s)}} \to {\bf{C}}{{\bf{r}}_{\bf{2}}}{{\bf{O}}_{\bf{3}}}{\bf{(s) + 4}}{{\bf{H}}_{\bf{2}}}{\bf{O(g) + }}{{\bf{N}}_{\bf{2}}}{\bf{(g)}}\)

(d) \({\bf{2Fe(s) + 3}}{{\bf{O}}_{\bf{2}}}{\bf{(g)}} \to {\bf{F}}{{\bf{e}}_{\bf{2}}}{{\bf{O}}_{\bf{3}}}{\bf{(s)}}\)
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