MC Part 2

2NO_2(g) + F_2(g) → 2NO₂F_(g)

The rate law for the reaction represented by the equation above is rate = k[NO₂][F₂]. Which of the following could be the first elementary step of a two-step mechanism for the reaction if the first step is slow and the second step is fast?

• F_2(g) → 2F_(g)

• NO_2(g) + F_2(g) → NO₂F_(g) + F_(g)

• NO_2(g) + F_(g) → NO₂F_(g)

• 2NO_2(g) + F_2(g) → 2NO₂F_(g)

Which of the following Lewis electron-dot diagrams represents the molecule that contains the smallest bond angles?

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• 
• 
• 

A mixture containing equal numbers of moles of ethyl acetate and butyl acetate was separated using distillation. Based on the diagrams shown, which of the following identifies the substance that would be initially present in higher concentrations in the distillate and correctly explains why that occurs?

• Ethyl acetate, because it has fewer C-C bonds to break

• Ethyl acetate, because it has a shorter carbon chain and weaker LDF's

• Butyl acetate, because it has more C-C bonds to break

• Butyl acetate, because it has longer carbon chain and weaker dipole-dipole

C₂₅H₃₀N₃⁺_(aq) + OH^-_(aq) → C₂₅H₃₀N₃OH_(aq)

Violet--------------------------colorless

The reaction between C₂₅H₃₀N₃⁺ and OH^-, as represented above, is first order with respect to C₂₅H₃₀N₃⁺ in the presence of excess OH^-. A 10.0mL sample of 0.10M NaOH(aq) is mixed with a 10.0mL sample of 2.5x10^-5M C₂₅H₃₀N₃⁺. A 5.0mL sample of the mixture is quickly transferred to a clean cuvette and placed in a spectrophotometer, and the progress of the reaction is measured. The data are given in the table.

Approximately how long did it take for 75 percent of the initial amount of C₂₅H₃₀N₃⁺ to react?

• 75s

• 225s

• 300s

• 600s

C₂₅H₃₀N₃⁺_(aq) + OH^-_(aq) → C₂₅H₃₀N₃OH_(aq)

Violet--------------------------colorless

The reaction between C₂₅H₃₀N₃⁺ and OH^-, as represented above, is first order with respect to C₂₅H₃₀N₃⁺ in the presence of excess OH^-. A 10.0mL sample of 0.10M NaOH(aq) is mixed with a 10.0mL sample of 2.5x10^-5M C₂₅H₃₀N₃⁺. A 5.0mL sample of the mixture is quickly transferred to a clean cuvette and placed in a spectrophotometer, and the progress of the reaction is measured.

What would be the effect on the reaction rate if the solution of C₂₅H₃₀N₃⁺ is diluted by a factor of two?

• It would be higher

• It would be lower

• It would not change

• It would initially be higher but then rapidly decrease

C₂₅H₃₀N₃⁺_(aq) + OH^-_(aq) → C₂₅H₃₀N₃OH_(aq)

Violet--------------------------colorless

To choose a wavelength to analyze the progress of the reaction above, a student records the absorbance spectra of both C₂₅H₃₀N₃⁺ and C₂₅H₃₀N₃OH in the range of 200-800nm. The two spectra are presented on the graph.

The student wants to use the spectrophotometer to measure [C₂₅H₃₀N₃⁺] with the greatest sensitivity as the reaction progresses. Which of the following indicates the best wavelength setting and explains why it is best?

• 205nm, because the colorless form of the molecule will absorb most

• 205nm, because both forms of the molecule will absorb best here

• 590nm, because only the violet form of the molecule will absorb best here

• 590nm, as this wavelength falls in the violet region of the visible light

CO_(g) + H₂O_(g) ↔ CO_2(g) + H_2(g) K_c = 1.5x10³

A 2.0mol sample of CO(g) and a 2.0mol sample of H2O(g) are introduced into a previously evacuated 100.L rigid container, and the temperature is held constant as the reaction represented above reaches equilibrium. Which of the following is true at equilibrium?

• [H₂O] > [CO] and [CO₂] > [H₂]

• [H₂O] > [H₂]

• [H₂O] > [H₂]

• [H₂O] = [CO] = [CO₂] = [H₂]

A 1.0L solution of AgNO_3(aq) and Pb(NO₃)_2(aq) has a Ag⁺ concentration of 0.020M and a Pb²⁺ concentration of 0.0010M. a 0.0010 mol sample of K₂SO_4(s) is added to the solution. Based on the information in the table, which of the following will occur? (Assume that the volume change of the solution is negligible)

• No precipitate will form

• Only Ag₂SO_4(s) will precipitate

• Only PbSO_4(s) will precipitate

• Both Ag₂SO_4(s) and PbSO_4(s) will precipitate

The pH of a 0.01M HNO_2(aq) solution is in which of the following ranges? (For HNO_2(aq), Ka=4.0x10^-4)

• Between 1 and 2

• Between 2 and 3

• Between 4 and 5

• Between 6 and 7

The photoelectron spectra of the 1s electrons of two isoelectronic species, Ca²⁺ and Ar, are shown in the table. Which of the following correctly identifies the species associated with peak X and provides a valid justification?

• Ar, because it has completely filled energy levels

• Ar, because its radius is smaller than the radius of Ca²⁺

• Ca²⁺, because its nuclear mass is greater than that of Ar

• Ca²⁺, because its nucleus has two more protons than the nucleus of Ar has