High School

Which of the following statements regarding the freezing and boiling points of these solutions are correct?

Solution I: 0.240 mol naphthalene in 2.45 mol of chloroform (M.W. = 119.4 g/mol)
Solution II: 1.50 g NaCl (M.W. = 58.44 g/mol) in 250 g of water
Solution III: 2.04 g KBr (M.W. = 119.0 g/mol) and 4.82 g glucose in 188 g of water

A. The freezing point of Solution I is -67.3 °C
B. The boiling point of Solution II is 100.1 °C
C. The freezing point of Solution III is -0.6 °C
D. The boiling point of Solution III is 100.2 °C
E. None of the above is correct

Which of the following descriptions about the atomic spectrum of the hydrogen atom are correct?

A. The atomic spectrum of the hydrogen atom is a continuous spectrum.
B. The energy required to remove the electron from a ground state hydrogen atom is \(2.178 \times 10^{18}\) J.
C. The first excitation means to move an electron from \(n=1\) to \(n=2\).
D. Transition from \(2p\) to \(1s\) emits a photon of wavelength 102 nm.
E. Transition of an electron from \(3p\) to \(1s\) releases more energy than a transition from \(3s\) to \(1s\).

Answer :

A. The freezing point of Solution I is -67.3 °C. This statement cannot be determined without knowing the freezing point depression constant of chloroform as the naphthalene will lower the freezing point of the solution.

B. The boiling point of Solution II is 100.1 °C. Correct. The boiling point of a solution is elevated due to the presence of a non-volatile solute like NaCl.

C. The freezing point of Solution III is -0.6 °C. This statement cannot be determined without knowing the freezing point depression constants of KBr and glucose in water.

D. The boiling point of Solution III is 100.2 °C. This statement cannot be determined without knowing the boiling point elevation constants of KBr and glucose in water.

E. None of the above is correct. This answer choice could be correct depending on the missing data.

For the atomic spectrum of hydrogen:

A. The atomic spectrum of hydrogen atom is a continuous spectrum. False. The atomic spectrum of hydrogen is a discrete line spectrum.

B. The energy required to remove the electron from a ground state hydrogen atom is 2.178 x 10^-18 J. True. This value is known as the ionization energy or the Rydberg constant.

C. The first excitation means to move an electron from n=1 to n = 2. True. The first excited state corresponds to an electron transition from the first energy level to the second energy level.

D. Transition from 2 to 1s emits a photon of wavelength 102 nm. False. This transition would emit a photon in the ultraviolet region, not 102 nm.

E. Transition of electron from 3p to 1s releases more energy than transition from 3p to 1s.True. The transition from a higher energy level to a lower energy level releases more energy than the reverse transition.

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