Kaplan MCAT General Chemistry Review

? = B[m²/(m²–2²)] = B[m²/(m²–n²)], where B = 364.56 nm, m > 2, is the wavelength, n is equal to 2.

The spectrum he used, which is now known as the Balmer series, is illustrated below:

The Rydberg equation is a more general version of this equation that applies to all possible energy level transitions in a hydrogen atom. Physicists used the Rydberg equation to detect other series of energy transitions in other regions of the light spectrum. One such series is the Lyman series, which accounts for transitions from excited states to n = 1, the ground state.

10. What is the proper electron configuration of hydrogen in its elemental state?

A. 1s⁰

B. 1s¹

C. 1s²

D. None of the above

11. If an electron is promoted from n = 2 to n = 5, as Balmer observed, which of the following possibilities BEST describes the source of the line spectra observed?

A. A photon is absorbed.

B. A photon is emitted.

C. An electron is absorbed.

D. An electron is emitted.

12. What region of the light spectrum corresponds to the characteristic emissions in the Balmer series?

A. UV

B. Visible

C. Infrared

D. X-ray

13. One Balmer spectral line, the n = 3 to n = 2 transition is a common reference point in astronomy for hydrogen gas emissions. The characteristic wavelength of this emission in the scientific literature is 656.3 nm. What color is this light emission?

A. Red

B. Blue-green

C. Violet

D. The emission is not in the visible spectrum.

14. What name BEST describes the absorption line spectrum pictured below?

A. Lyman series

B. Balmer series

C. Bohr series

D. None of the above

15. Suppose a scientist tried to obtain a Balmer series with a sample of deuterium. How would this sample change the appearance of the emissions in the line spectrum?

A. Fewer emission lines

B. More emission lines

C. Same number of emission lines with split peaks

D. Same number of emission lines without split peaks (that is, no change in appearance)

16. At high resolution, some of the emissions in the Balmer series appear as doublets. Which of the following BEST explains this result, which was not predicted by any of the models in the passage?

A. The models in the passage do not account for relativistic effects.

B. The models in the passage do not account for high wavelengths.

C. The models in the passage do not account for the atomic number.

D. The models in the passage do not account for other particles in the atom.

17. When n > 6, the Balmer series features violet light emissions at wavelengths outside the range of the visible spectrum. Which of the following BEST accounts for this finding?

A. Energy levels are narrower as n 1 and wider as n 8.

B. Energy levels are wider as n 1 and narrower as n 8.

C. Energy differences between levels are larger as n 1 and smaller as n 8.

D. Energy differences between levels are smaller as n 1 and larger as n 8.

QUESTIONS 18–22 ARE NOT BASED ON A DESCRIPTIVE PASSAGE.

18. Which of the following pairs of particles would be accelerated in a particle accelerator?

A. Gamma ray and neutron

B. Gamma ray and beta particle

C. Beta particle and neutron

D. Alpha and beta particles

19. What volume of 0.5 M KOH would be necessary to neutralize 15 mL of 1 M nitrous acid?

A. 15 mL

B. 30 mL

C. 45 mL

D. 60 mL

20. Why does high, but not low, pressure cause a deviation from the ideal gas law?

A. Higher pressure decreases the interatomic distance to the point where intermolecular forces reduce the volume below that predicted by the ideal gas equation.

B. Low pressure increases the atomic radius of a gas making it more stable whereas high pressure compresses the gas particles decreasing their stability.

C. Low pressure does cause a significant deviation from the ideal gas law because the increased interatomic distance means that no particles ever collide.

D. Low pressure does cause a significant deviation because a low pressure implies a reduction in temperature via Charles’ law, which increases the power of intermolecular forces.

21. What type of molecular geometry is NOT able to result in a nonpolar structure?

A. Bent

B. Diatomic covalent

C. Trigonal planar

D. Square planar

22. A parent and daughter nucleus are isotypes of the same element. Therefore, the ratio of alpha to beta decays that produced the daughter nucleus must be which of the following?

A. 2:3

B. 2:1

C. 1:2

D. 1:1

PASSAGE III (QUESTIONS 23–30)

Many new consumer electronics and electric cars utilize a type of rechargeable battery that extracts its power from the movement of a lithium ion (Li⁺) between the cathode and the anode of a galvanic cell. In most cases, the anode is composed of graphite, the cathode is composed of a CoO₂^- complex, and the electrolyte contains a lithium salt in an organic solvent. Following are the half-reactions, where Li_1-xCoO₂ is the simplest form of the chemical formula Li(CoO₂)_1/(1-x) (which represents a complex of one lithium ion with several metal oxide molecules):

LiCoO₂Li_1-xCoO₂ + xLi⁺ + xe^- (cathode)