Chapter 16

Distinguish between a complex reaction, a reaction mechanism, and an elementary step.

Suppose that a chemical reaction takes place in a two-step mechanism. Step 1 (fast) \(\mathrm{A}+\mathrm{B} \rightarrow \mathrm{C}\) Step \(2(\text { slow }) \mathrm{C}+\mathrm{D} \rightarrow \mathrm{E}\) Which step in the reaction mechanism is the ratedetermining step? Explain.

Dinitrogen pentoxide decomposes in chloroform at a rate of \(2.48 \times 10^{-4} \mathrm{mol} /(\mathrm{L} \cdot \mathrm{min})\) at a particular temperature according to the equation \(2 \mathrm{N}_{2} \mathrm{O}_{5} \rightarrow 4 \mathrm{NO}_{2}+\mathrm{O}_{2}\) The reaction is first order in \(\mathrm{N}_{2} \mathrm{O}_{5}\) . Given an initial concentration 0.400 \(\mathrm{mol} / \mathrm{L}\) , what is the rate constant for the reaction? What is the approximate \(\left[\mathrm{N}_{2} \mathrm{O}_{5}\right]\) after the reaction proceeds for 1.30 \(\mathrm{h}\) ?

Radioactive decay is first order in the decaying isotope. For example, strontium-90 contained in fallout from nuclear explosions decays to yttrium-90 and a beta particle. Write the rate law for the decay of strontium-90.

Evaluate the validity of this statement: You can determine the rate law for a chemical reaction by examining the mole ratio of reactants in the balanced equation. Explain your answer.

The concentration of Reactant A decreases from 0.400 \(\mathrm{mol} / \mathrm{L}\) at 0.00 \(\mathrm{min}\) to 0.384 \(\mathrm{mol} / \mathrm{L}\) at 4.00 \(\mathrm{min}\) . Calculate the average reaction rate during this time period. Express the rate in mol/(L. min).

If the concentration of a reaction product increases from 0.0882 \(\mathrm{mol} / \mathrm{L}\) to 0.1446 \(\mathrm{mol} / \mathrm{L}\) in 12.0 minutes, what is the average reaction rate during the time interval?

A two-step mechanism has been proposed for the decomposition of nitryl chloride \(\left(\mathrm{NO}_{2} \mathrm{CL}\right)\) Step \(1 : \mathrm{NO}_{2} \mathrm{Cl}(\mathrm{g}) \rightarrow \mathrm{NO}_{2}(\mathrm{g})+\mathrm{Cl}(\mathrm{g})\) Step \(2 : \mathrm{NO}_{2} \mathrm{Cl}(\mathrm{g})+\mathrm{Cl}(\mathrm{g}) \rightarrow \mathrm{NO}_{2}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{g})\) What is the overall reaction? Identify any intermediates in the reaction sequence, and explain why they are called intermediates

Automobile Engine The following reaction takes place in an automobile’s engine and exhaust system. $$\mathrm{NO}_{2}(\mathrm{g})+\mathrm{CO}(\mathrm{g}) \rightarrow \mathrm{NO}(\mathrm{g})+\mathrm{CO}_{2}(\mathrm{g})$$ The reaction's rate law at a particular temperature is Rate \(=0.50 \mathrm{L} /(\mathrm{mol} \cdot \mathrm{s})\left[\mathrm{NO}_{2}\right]^{2}\) . What is the reaction's initial, instantaneous rate when \(\left[\mathrm{NO}_{2}\right]=0.0048 \mathrm{mol} / \mathrm{L} ?\)

The concentrations in a chemical reaction are expressed in moles per liter and time is expressed in seconds. If the overall rate law is third-order, what are the units for the rate and the rate constant?

Apply the method of initial rates to determine the order of a chemical reaction with respect to Reactant \(X\) . Create a set of hypothetical experimental data that would lead you to conclude that the reaction is second order in \(X .\)

Formulate a rationale to explain how a complex chemical reaction might have more than one rate-determining elementary step.

Apply collision theory to explain two reasons why increasing the temperature of a reaction by 10 \(\mathrm{K}\) often doubles the reaction rate.

Hydrocarbons Heating cyclopropane \(\left(\mathrm{C}_{3} \mathrm{H}_{6}\right)\) converts it to propene \(\left(\mathrm{CH}_{2}=\mathrm{CHCH}_{3}\right) .\) The rate law is first order in cyclopropane. If the rate constant at a particular temperature is \(6.22 \times 10^{-4} \mathrm{s}^{1}\) and the concentration of cyclopropane is held at 0.0300 \(\mathrm{mol} / \mathrm{L}\) , what mass of propene is produced in 10.0 \(\mathrm{min}\) in a volume of 2.50 \(\mathrm{L} ?\)

For the following categories of elements, state the possible number(s) of electrons in their outermost orbitals in the ground state? (Chapter 5) a. \(\mathrm{p}\) -block elements b. nitrogen-group elements c. d-block elements d. noble-gas elements e. s-block elements

Classify each of the following elements as a metal, nonmetal, or metalloid. (Chapter 6) a. molybdenum b. bromine c. arsenic d. neon e. cerium

Balance the following equations. (Chapter 9) a. \(\operatorname{Sn}(s)+\mathrm{NaOH}(\mathrm{aq}) \rightarrow \mathrm{Na}_{2} \mathrm{SnO}_{2}+\mathrm{H}_{2}\) b. \(\mathrm{C}_{8} \mathrm{H}_{18}(1)+\mathrm{O}_{2}(\mathrm{g}) \rightarrow \mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(1)\) c. \(\mathrm{Al}(\mathrm{s})+\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \rightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})\)

What mass of iron(III) chloride is needed to prepare 1.00 \(\mathrm{L}\) of a 0.255 \(\mathrm{M}\) solution? (Chapter 14\()\)

\(\Delta H\) for a reaction is negative. Compare the energy of the products and the reactants. Is the reaction endothermic or exothermic? (Chapter 15\()\)

The rate law is rate \(=k[\text { phenolphthalein }] .\) If the rate constant for the reaction is \(1.0 \times 10^{-2} \mathrm{s}^{-1}\) , what is the instantaneous rate of reaction when the concentration of phenolphthalein is 0.0025\(M\) ?