Chemical Reactions and Equations

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Questions and Answers

Consider a closed system containing initially only diatomic hydrogen and oxygen gases. Under what precise conditions, considering temperature, pressure, and the presence of specific catalysts, will the reaction $2H_2(g) + O_2(g) \rightleftharpoons 2H_2O(g)$ proceed such that the equilibrium mixture contains no detectable unreacted oxygen, assuming ideal gas behavior and perfect mixing?

Under standard conditions ($298 \mathrm{K}$, $1 \mathrm{atm}$) with a platinum catalyst; the reaction will invariably proceed to completion due to thermodynamic favorability.
With a stoichiometric excess of hydrogen at moderate temperatures ($500-700 \mathrm{K}$) and optimized pressure using a palladium catalyst, followed by immediate product removal to shift equilibrium. (correct)
At extremely high temperatures ($>2000 \mathrm{K}$) and pressures ($>100 \mathrm{atm}$) in the absence of any catalyst to overcome kinetic barriers, ensuring all oxygen is consumed.
Under cryogenic conditions (near absolute zero) to suppress the reverse reaction, combined with intense UV irradiation to initiate homolytic cleavage of $O_2$ and subsequent rapid reaction with $H_2$.

Given the reaction $AgNO_3(aq) + NaCl(aq) \rightarrow AgCl(s) + NaNO_3(aq)$, under what non-standard conditions (i.e., deviating from $25^\circ C$ and 1 atm) would the apparent equilibrium constant ($K_{app}$) be most significantly affected, considering activity coefficients and complex ion formation?

High ionic strength solutions (e.g., $1 M$ $KNO_3$) where the Debye-Hckel theory accurately predicts activity coefficient changes, leading to a predictable shift in $K_{app}$.
Supercooled solutions far below the freezing point of water, drastically reducing ion mobility and thus slowing down both the forward and reverse reaction rates equally, leaving $K_{app}$ unchanged.
Extremely dilute solutions ($<10^{-6} M$), where ion pairing is negligible and activity coefficients approach unity, thereby minimizing deviations from ideality.
Solutions with a significant concentration of ammonia ($NH_3$), facilitating the formation of silver ammine complexes ($[Ag(NH_3)_2]^+$), thereby increasing the apparent solubility of $AgCl$. (correct)

In the context of redox reactions, consider a scenario where elemental iron ($Fe$) is immersed in a copper sulfate ($CuSO_4$) solution. What specific alteration to the solution's propertiesbeyond simple concentration changeswould most effectively suppress the spontaneous displacement reaction, $Fe(s) + CuSO_4(aq) \rightarrow FeSO_4(aq) + Cu(s)$, based on electrochemical principles?

Saturating the solution with an inert salt (e.g., $Na_2SO_4$) to increase the ionic strength, minimizing the activity coefficients of the redox-active ions and thus inhibiting electron transfer.
Increasing the temperature to near boiling, thereby enhancing the kinetic energy of the ions and favoring the reverse reaction due to Le Chatelier's principle.
Applying an external potential using a potentiostat to maintain the iron electrode at a more positive potential than its standard reduction potential, effectively reversing the driving force of the reaction. (correct)
Introducing a strong chelating agent (e.g., EDTA) that selectively binds with $Fe^{2+}$ ions, significantly lowering their concentration in solution and shifting the equilibrium to favor the reactants.

Given the balanced chemical equation $2H_2 + O_2 \rightarrow 2H_2O$, performed under non-ideal conditions where the activity coefficients of the reactants and products deviate significantly from unity, how would one accurately determine the Gibbs Free Energy change ($\Delta G$) for this reaction at a specific non-standard state, accounting for these non-idealities?

<p>Use empirical relationships (e.g., Guggenheim or Davies equations) to estimate activity coefficients at the given ionic strength and temperature, then adjust the chemical potentials of each species accordingly before calculating $\Delta G$. (D)</p> Signup and view all the answers

Consider a complex reaction mechanism involving multiple elementary steps, where the rate-determining step exhibits a significant kinetic isotope effect (KIE) when deuterium ($D$) is substituted for protium ($H$). How would this KIE quantitatively impact the observed overall reaction rate, and what specific experimental technique could unequivocally confirm that the measured KIE corresponds exclusively to the rate-determining step?

<p>The overall reaction rate would be reduced by a factor roughly corresponding to the zero-point energy difference between C-H and C-D bonds in the rate-determining step, verifiable through computational chemistry calculations and site-selective mutagenesis. (A)</p> Signup and view all the answers

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Flashcards

Chemical Reaction

Transformation of reactants into products with a change in composition.

Balanced Chemical Equation

An equation with equal numbers of each atom on both sides, obeying mass conservation.

Redox Reaction

A reaction involving the transfer of electrons between two substances.

Displacement Reaction

A reaction where one element replaces another in a compound.

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Example of a Redox Reaction

H + Cl → 2HCl demonstrates electron transfer.

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Study Notes

Chemical Reactions and Equations

A chemical reaction is a process where reactants change into products with a change in chemical composition. Example: 2H₂ + O₂ → 2H₂O (Formation of water).
A balanced chemical equation ensures the law of conservation of mass is followed. It has an equal number of atoms of each element on both sides of the equation.
Redox reactions involve a transfer of electrons. An example of a redox reaction is: H₂ + Cl₂ → 2HCl.
Displacement reactions involve one element replacing another in a compound. Example: Fe + CuSO₄ → FeSO₄ + Cu.