Chapter 15: Problem 2
Why are reaction rates important (both practically and theoretically)?
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chapter 15: Problem 2
Why are reaction rates important (both practically and theoretically)?
These are the key concepts you need to understand to accurately answer the question.
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Get started for freeWhy is the reaction rate for reactants defined as the negative of the change in reactant concentration with respect to time, whereas for products it is defined as the change in reactant concentration with re- spect to time (with a positive sign)?
The desorption of a single molecular layer of \(n\) -butane from a single crystal of aluminum oxide is found to be first order with a rate constant of 0.128\(/ \mathrm{s}\) at 150 \(\mathrm{K}\) . \begin{equation} \begin{array}{l}{\text { a. What is the haff-life of the desorption reaction? }} \\ {\text { b. If the surface is initially completely covered with } n \text { -butane at }} \\ {150 \mathrm{K}, \text { how long will it take for } 25 \% \text { of the molecules to desorb? For }} \\ {50 \% \text { to desorb? }}\\\\{\text { c. If the surface is initially completely covered, what fraction will remain }} \\ {\text { covered after } 10 \text { s? After } 20 \mathrm{s?}}\end{array} \end{equation}
What are the units of \(k\) for each type of reaction? \begin{equation} \begin{array}{l}{\text { a. first-order reaction }} \\ {\text { b. second- order reaction }} \\ {\text { c. } \text { zero-order reaction }}\end{array} \end{equation}
The half-life for the radioactive decay of \(\mathrm{C}-14\) is 5730 years and is inde- pendent of the initial concentration. How long does it take for 25\(\%\) of the C-14 atoms in a sample of \(C-14\) to decay? If a sample of C-14 initially contains 1.5 mmol of C-14, how many millimoles are left after 2255 years?
The energy of activation for the decomposition of 2 mol of \(\mathrm{HI}\) to \(\mathrm{H}_{2}\) and \(\mathrm{I}_{2}\) in the gas phase is 185 \(\mathrm{kJ}\) . The heat of formation of \(\mathrm{HI}(g)\) from \(\mathrm{H}_{2}(g)\) and \(\mathrm{I}_{2}(g)\) is \(-5.68 \mathrm{kJ} / \mathrm{mol} .\) Find the energy of activation for the reaction of 1 \(\mathrm{mol}\) of \(\mathrm{H}_{2}\) and 1 \(\mathrm{mol}\) of \(\mathrm{I}_{2}\) to form 2 mol of HI in the gas phase.
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