Chapter 14: Problem 3
What are the advantages of measuring the initial rate of a reaction?
Chapter 14: Problem 3
What are the advantages of measuring the initial rate of a reaction?
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Get started for freeA quantity of \(6 \mathrm{~g}\) of granulated \(\mathrm{Zn}\) is added to a solution of \(2 M \mathrm{HCl}\) in a beaker at room temperature. Hydrogen gas is generated. For each of the following changes (at constant volume of the acid) state whether the rate of hydrogen gas evolution will be increased, decreased, or unchanged: (a) \(6 \mathrm{~g}\) of powdered \(\mathrm{Zn}\) is used; \((\mathrm{b}) 4 \mathrm{~g}\) of granulated \(\mathrm{Zn}\) is used; \((\mathrm{c})\) \(2 M\) acetic acid is used instead of \(2 M \mathrm{HCl} ;\) d) temperature is raised to \(40^{\circ} \mathrm{C}\).
(a) What can you deduce about the activation energy of a reaction if its rate constant changes significantly with a small change in temperature? (b) If a bimolecular reaction occurs every time an A and a B molecule collide, what can you say about the orientation factor and activation energy of the reaction?
Sketch a potential-energy-versus-reaction-progress plot for the following reactions: $$ \begin{array}{l} \text { (a) } \mathrm{S}(s)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{SO}_{2}(g) \\ \Delta H^{\circ}=-296.06 \mathrm{~kJ} / \mathrm{mol} \\ \text { (b) } \mathrm{Cl}_{2}(g) \longrightarrow \mathrm{Cl}(g)+\mathrm{Cl}(g) \\\ \Delta H^{\circ}=242.7 \mathrm{~kJ} / \mathrm{mol} \end{array} $$
In recent years ozone in the stratosphere has been depleted at an alarmingly fast rate by chlorofluorocarbons (CFCs). A CFC molecule such as \(\mathrm{CFCl}_{3}\) is first decomposed by UV radiation: $$ \mathrm{CFCl}_{3} \longrightarrow \mathrm{CFCl}_{2}+\mathrm{Cl} $$ The chlorine radical then reacts with ozone as follows: $$ \begin{array}{c} \mathrm{Cl}+\mathrm{O}_{3} \longrightarrow \mathrm{ClO}+\mathrm{O}_{2} \\ \mathrm{ClO}+\mathrm{O} \longrightarrow \mathrm{Cl}+\mathrm{O}_{2} \end{array} $$ (a) Write the overall reaction for the last two steps. (b) What are the roles of \(\mathrm{Cl}\) and \(\mathrm{ClO} ?\) (c) Why is the fluorine radical not important in this mechanism? (d) One suggestion to reduce the concentration of chlorine radicals is to add hydrocarbons such as ethane \(\left(\mathrm{C}_{2} \mathrm{H}_{6}\right)\) to the stratosphere. How will this Work?
Explain why termolecular reactions are rare.
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