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Chapter 17: Problem 42

A student placed \(1 \mathrm{~g}\) of each of three compounds A, B, and C in a container and found that after 1 week no change had occurred. Offer some possible explanations for the fact that no reactions took place. Assume that \(\mathrm{A}, \mathrm{B},\) and \(\mathrm{C}\) are totally miscible liquids.

Short Answer

Expert verified
No reaction occurred, possibly due to one or more of these reasons: 1) Compounds A, B and C do not chemically interact with each other, 2) The energy was too low to provide the necessary activation energy for reaction, 3) A needed catalyst was absent, or 4) A specific condition such as temperature, pressure or light was missing.

Step by step solution

01

Understand the Situation

First, understand that three substances A, B, and C are mixed together in a container and they are left for a week. After that time period, no changes were observed. Even though these substances are completely miscible, no reactions occur.
02

Recall the essentials for a Chemical Reaction to occur

Recall that for a chemical reaction to occur, substances need to react with each other to form new products. These reactions take place when the reacting substances' molecules collide with sufficient energy and proper orientation.
03

Contemplate about lack of chemical reaction

Given that no reaction occurred, it is possible that one of the conditions necessary for a chemical reaction didn't take place. On one hand, it can be presumed that compounds A, B and C do not react with each other. On the other hand, it may be possible that the reaction does occur, but not at the conditions provided in the situation.
04

Consider potential specific reasons

Each compound may be unreactive or chemically inert; similar to noble gases or substances like graphite and glass. Another potential reason could be that the energy of the system was too low to provide the activation energy necessary for the reaction. Possibly, a catalyst is required to decrease the activation energy of the reaction, and without it, the reaction did not take place. Alternatively, a specific condition could be lacking like a certain temperature or pressure, pH level, or even certain kind of light that might be necessary to provoke the reaction.

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Most popular questions from this chapter

Calculate \(\Delta G^{\circ}\) for the following reactions at \(25^{\circ} \mathrm{C}\) : (a) \(2 \mathrm{Mg}(s)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{MgO}(s)\) (b) \(2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{SO}_{3}(g)\) (c) \(2 \mathrm{C}_{2} \mathrm{H}_{6}(g)+7 \mathrm{O}_{2}(g) \longrightarrow\) $$ 4 \mathrm{CO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(l) $$ See Appendix 2 for thermodynamic data.

Predict whether the entropy change is positive or negative for each of these reactions: (a) \(\mathrm{Zn}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{ZnCl}_{2}(a q)+\mathrm{H}_{2}(g)\) (b) \(\mathrm{O}(g)+\mathrm{O}(g) \longrightarrow \mathrm{O}_{2}(g)\) (c) \(\mathrm{NH}_{4} \mathrm{NO}_{3}(s) \longrightarrow \mathrm{N}_{2} \mathrm{O}(g)+2 \mathrm{H}_{2} \mathrm{O}(g)\) (d) \(2 \mathrm{H}_{2} \mathrm{O}_{2}(l) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{O}_{2}(g)\)

Use the following data to determine the normal boiling point, in kelvins, of mercury. What assumptions must you make in order to do the calculation? $$ \begin{aligned} \mathrm{Hg}(l): & \Delta H_{\mathrm{f}}^{\circ} &=0 \text { (by definition) } \\\ & S^{\circ} &=77.4 \mathrm{~J} / \mathrm{K} \cdot \mathrm{mol} \\ \mathrm{Hg}(g): & \Delta H_{\mathrm{f}}^{\circ} &=60.78 \mathrm{~kJ} / \mathrm{mol} \\ & S^{\circ} &=174.7 \mathrm{~J} / \mathrm{K} \cdot \mathrm{mol} \end{aligned} $$

Explain what is meant by a spontaneous process. Give two examples each of spontaneous and nonspontaneous processes.

In each of the following reactions, there is one species for which the standard entropy value is not listed in Appendix \(2 .\) Determine the \(S^{\circ}\) for that species. (a) The \(\Delta S_{\mathrm{rxn}}^{\circ}\) for the reaction \(\mathrm{Na}(s) \longrightarrow \mathrm{Na}(l)\) is \(48.64 \mathrm{~J} / \mathrm{K}\) mol. (b) The \(\Delta S_{\mathrm{rxn}}^{\circ}\) for the reaction \(2 \mathrm{~S}\) (monoclinic) \(+\) \(\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{S}_{2} \mathrm{Cl}_{2}(g)\) is \(43.4 \mathrm{~J} / \mathrm{K} \cdot \mathrm{mol} .\) (c) The \(\Delta S_{\mathrm{rxn}}^{\circ}\) for the reaction \(\mathrm{FeCl}_{2}(s) \longrightarrow \mathrm{Fe}^{2+}(a q)+2 \mathrm{Cl}^{-}(a q)\) is \(-118.3 \mathrm{~J} / \mathrm{K} \cdot \mathrm{mol}\)
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