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Chapter 4: Problem 4

The concept of chemical equilibrium is very important. Which one of the following statements is the most correct way to think about equilibrium? (a) If a system is at equilibrium, nothing is happening. (b) If a system is at equilibrium, the rate of the forward reaction is equal to the rate of the back reaction. (c) If a system is at equilibrium, the product concentration is changing over time. [Section 4.1\(]\)

Short Answer

Expert verified
The most correct statement about chemical equilibrium is: \( (b) \) If a system is at equilibrium, the rate of the forward reaction is equal to the rate of the back reaction.

Step by step solution

01

(a) If a system is at equilibrium, nothing is happening.

A common misconception is that at equilibrium, the reaction stops. In reality, a system at equilibrium is still dynamic, meaning the forward and reverse reactions continue to occur, but at the same rate. This statement is not the most correct.
02

(b) If a system is at equilibrium, the rate of the forward reaction is equal to the rate of the back reaction.

Chemical equilibrium occurs when the rate of the forward reaction is equal to the rate of the reverse reaction. This means that the concentrations of the reactants and products remain constant over time, and the overall reaction appears to have stopped. However, the forward and reverse reactions are still occurring at the same rate. This statement correctly describes the concept of chemical equilibrium.
03

(c) If a system is at equilibrium, the product concentration is changing over time.

If a system is at equilibrium, the concentrations of reactants and products remain constant, because the forward and reverse reactions are occurring at the same rate. Therefore, this statement is not accurate. Based on the analysis above, the most correct statement about chemical equilibrium is:
04

Most correct statement:

(b) If a system is at equilibrium, the rate of the forward reaction is equal to the rate of the back reaction.

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Most popular questions from this chapter

Ignoring protolysis reactions, indicate the concentration of each ion or molecule present in the following solu- tions: (a) \(0.35 \mathrm{MK}_{3} \mathrm{PO}_{4},\) (b) $5 \times 10^{-4} \mathrm{MCuCl}_{2},(\mathbf{c}) 0.0184$ \(\mathrm{MCH}_{3} \mathrm{CH}_{2} \mathrm{OH}(\mathbf{d})\) a mixture of $35.0 \mathrm{~mL}\( of \)0.010 \mathrm{MNa}_{2} \mathrm{CO}_{3}$ and \(50.0 \mathrm{~mL}\) of \(0.200 \mathrm{MK}_{2} \mathrm{SO}_{4}\). Assume the volumes are additive.

Some sulfuric acid is spilled on a lab bench. You can neutralize the acid by sprinkling sodium bicarbonate on it and then mopping up the resulting solution. The sodium bicarbonate reacts with sulfuric acid according to: $$ \begin{aligned} 2 \mathrm{NaHCO}_{3}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+& \\ & 2 \mathrm{H}_{2} \mathrm{O}(l)+2 \mathrm{CO}_{2}(g) \end{aligned} $$ Sodium bicarbonate is added until the fizzing due to the formation of \(\mathrm{CO}_{2}(g)\) stops. If \(27 \mathrm{~mL}\) of $6.0 \mathrm{MH}_{2} \mathrm{SO}_{4}\( was spilled, what is the minimum mass of \)\mathrm{NaHCO}_{3}$ that must be added to the spill to neutralize the acid?

The arsenic in a \(1.22-g\) sample of a pesticide was converted to \(\mathrm{AsO}_{4}^{3-}\) by suitable chemical treatment. It was then titrated using \(\mathrm{Ag}^{+}\) to form \(\mathrm{Ag}_{3} \mathrm{AsO}_{4}\) as a precipitate. (a) What is the oxidation state of As in $\mathrm{AsO}_{4}{ }^{3-} ?(\mathbf{b})\( Name \)\mathrm{Ag}_{3} \mathrm{AsO}_{4}$ by analogy to the corresponding compound containing phosphorus in place of arsenic. (c) If it took \(25.0 \mathrm{~mL}\) of \(0.102 \mathrm{MAg}^{+}\) to reach the equivalence point in this titration, what is the mass percentage of arsenic in the pesticide?

As \(\mathrm{K}_{2} \mathrm{O}\) dissolves in water, the oxide ion reacts with water molecules to form hydroxide ions. (a) Write the molecular and net ionic equations for this reaction. (b) Based on the definitions of acid and base, what ion is the base in this reaction? (c) What is the acid in the reaction? (d) What is the spectator ion in the reaction?

Federal regulations set an upper limit of 50 parts per million (ppm) of \(\mathrm{NH}_{3}\) in the air in a work environment [that is, 50 molecules of \(\mathrm{NH}_{3}(g)\) for every million molecules in the air]. Air from a manufacturing operation was drawn through a solution containing $1.00 \times 10^{2} \mathrm{~mL}\( of \)0.0105 \mathrm{MHCl} .\( The \)\mathrm{NH}_{3}$ reacts with HCl according to: $$ \mathrm{NH}_{3}(a q)+\mathrm{HCl}(a q) \longrightarrow \mathrm{NH}_{4} \mathrm{Cl}(a q) $$ After drawing air through the acid solution for \(10.0 \mathrm{~min}\) at a rate of \(10.0 \mathrm{~L} / \mathrm{min},\) the acid was titrated. The remaining acid needed \(13.1 \mathrm{~mL}\) of \(0.0588 \mathrm{M} \mathrm{NaOH}\) to reach the equivalence point. (a) How many grams of \(\mathrm{NH}_{3}\) were drawn into the acid solution? (b) How many ppm of \(\mathrm{NH}_{3}\) were in the air? (Air has a density of \(1.20 \mathrm{~g} / \mathrm{L}\) and an average molar mass of \(29.0 \mathrm{~g} / \mathrm{mol}\) under the conditions of the experiment.) (c) Is this manufacturer in compliance with regulations?
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