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Exam 1 Quy

Exam 1 Quy - Version 040 Exam 1 quy(50970 This print-out...

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Version 040 – Exam 1 – quy – (50970) 1 This print-out should have 31 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0points If a photon’s wavelength is 663 μ m, what is its energy in Joules? 1. 3 . 00 × 10 25 J 2. 3 . 00 × 10 28 J 3. 3 . 00 × 10 22 J correct 4. 4 . 40 × 10 43 J 5. 4 . 40 × 10 40 J 6. 4 . 40 × 10 46 J Explanation: λ = 663 μ m c = 3 × 10 8 m/s h = 6 . 626 × 10 34 J · s. For a photon c = λν, so E = = hc λ where c is the speed of light and h is Planck’s constant. E = hc λ = ( 6 . 63 × 10 34 J · s )( 3 × 10 8 m / s ) × parenleftbigg 1 663 μ m parenrightbiggparenleftbigg 10 6 μ m 1 m parenrightbigg = 3 × 10 22 J 002 10.0points Which of the following valence-shell config- urations 4 s 4 p I) ↑↓ ↑↓ II) ↑↓ III) IV) ↑↓ could describe a neutral atom in its ground state? 1. I only 2. IV only correct 3. II only 4. None of the configurations 5. More than one of the configurations 6. III only Explanation: The atom with a 4 s 2 4 p 2 valence-shell con- figuration is germanium (Ge). The ground- state configuration is given by ↑↓ The other configurations represent excited states. 003 10.0points In a given atom, what is the largest possible number of 3 p electrons? 1. 18 2. 10 3. 2 4. 6 correct 5. 5 Explanation: The p sublevel has 3 orbitals, each of which can hold up to 2 electrons, so the p sublevel can hold up to 6 electrons. 004 10.0points Paired electrons in the same atom will differ because of their 1. location. 2. mass.

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Version 040 – Exam 1 – quy – (50970) 2 3. charge. 4. spin. correct Explanation: Paired electrons have similar quantum numbers; only the spin quantum number dis- tinguishes one from the other. 005 10.0points Which response identifies a possible ψ for the last-filled electron in a chloride ion? 1. ψ 2 , 1 , 2 2. ψ 3 , 3 , 1 3. ψ 2 , 0 , 0 4. ψ 3 , 1 , 1 correct 5. ψ 3 , 0 , 0 6. ψ 2 , 0 , 1 Explanation: The ψ are written in format ψ n,ℓ,m . The electronic configuration for the chloride ion is [Ne] 3 s 2 3 p 6 , so the last-filled electron is in 3 p . For the 3 p orbital, n = 3, = 1, and m can be - 1 , 0 , +1. (The m can be any of those values because the orbitals are degenerate, so may fill in any order.) 006 10.0points The optical spectrum of an atom can be used to distinguish it from all other kinds of atoms. 1. True correct 2. False Explanation: The optical spectrum comes from the en- ergies of the electrons in the atom, which in turn comes from the p + - e and e - e forces in the atom. Since each element differs in these forces, each element’s optical spectrum is unique. 007 10.0points The average speed of a helium atom at 25 C is 1 . 23 × 10 3 m / s. What is the average wave- length of a helium atom at this temperature? 1. 4 . 06 × 10 11 m 2. 2 . 03 × 10 11 m 3. 8 . 11 × 10 11 m correct 4. 4 . 15 × 10 12 m 5. 7 . 43 × 10 15 m Explanation: v = 1 . 23 × 10 3 m / s The mass of one He atom is mass He = 4 . 00 g / mol 6 . 022 × 10 23 atoms / mol = 6 . 64 × 10 24 g = 6 . 64 × 10 27 kg Using de Broglie’s relationship, λ = h p = h mv = 6 . 626 × 10 34 kg · m 2 / s (6 . 64 × 10 27
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Exam 1 Quy - Version 040 Exam 1 quy(50970 This print-out...

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