Exam #1 Practice PDF

EXAM # 1 PRACTICE Students Name PENN ID# EXAM INSTRUCTIONS There are 20 questions (on 8 pages) worth a total of 100 points This exam is closed-book/c...

EXAM # 1 PRACTICE Students Name PENN ID# EXAM INSTRUCTIONS There are 20 questions (on 8 pages) worth a total of 100 points This exam is closed-book/closed-notes. You must use a black/blue pen or pencil (no red or similarly colored pens). You must fill in your multiple-choice answers before time is called. It is unfair to get extra time when others have filled in their answers in the appropriate time frame. Where you are asked to briefly explain, please limit your answer to 2 – 3 sentence Show all work in spaces provided – the back of the exam is only to be used for scratch work Partial credit will be awarded for part III of this exam. Show ALL your work NEATLY!!! Please read the following statement carefully and sign below: I agree to abide by the provisions of the Code of Academic Integrity and I certify that I have complied with the Code of Academic Integrity in taking this examination. Compliance includes: The agreement to use my calculator ONLY as a CALCULATION aid The pledge that NO other electronic or wireless devices are used in any capacity, including calculators that can access any network. All answers submitted are my own work Signature: ___________________ Multiple Choice Answers [36 points] 1 5 9 2 6 10 3 7 11 4 8 12 You MAY NOT detach the front page from the exam. You MAY detach the reference page from the exam. 1 Part I: Multiple choice [42 points] 1. 1.00 oz of gold (density = 19.3 g/mL) can be hammered into a sheet that would cover a area. How thick would such a sheet be in centimeters? (1 oz= 28.350 g) A) 1.58 × 10-5 cm B) 4.82 × 10-4 cm C) 4.02 × 10-5 cm D) 6.33 × 104 cm E) 2.11 × 10-5 cm 2. How many significant figures should the answer to the following calculation have? -2 (1.4312 - 1.1 × 10 ) ÷ (1.0712 × 10-4) a) 4 b) 5 c) 2 d) 3 3. The temperature in the core of the warp drive of the starship Enterprise is supposedly 3 million (3.00 × 106) degrees Celsius. What is this in degrees Fahrenheit? 6 A) 5.40 × 10 °F 6 B) 2.99 × 10 °F 6 C) 1.67 × 10 °F 6 D) 3.27 × 10 °F 6 E) 8.13 × 10 °F 4. Which of these atoms has the greatest number of neutrons in its nucleus? a. Ni b. Co c. Fe d. Mn e. Si 5. What is the mass in grams of 1 atom of sulfur -24 A) 1.661 × 10 g -25 B) 1.931 × 10 g -23 C) 5.325 × 10 g -26 D) 5.179 × 10 g -23 E) 5.989 × 10 g 6. The natural abundance of calcium in the earth's crust is 3.4% by mass. How many calcium atoms are present in a 1.50 g sample of the earth's crust? 23 A) 6.6 × 10 atoms 22 B) 3.1 × 10 atoms 20 C) 7.7 × 10 atoms 22 D) 7.7 × 10 atoms 20 E) 5.1 × 10 atoms 2 7. A cation has 13 neutrons and 10 electrons. If it has a charge of +1, what is its correct symbol? a. b. c. d. d. 24 25 8. The three naturally occurring isotopes of magnesium are Mg (23.985042 u, 78.99%), Mg (24.985837, 26 26 10.00%), and Mg. What is the atomic mass of Mg? A) 25.98 u B) 48.67 u C) 23.94 u D) 26.43 u E) 24.31 u 9. The Bohr theory explains that an emission spectral line is: a. due to an electron losing energy but keeping the same values of its four quantum numbers b. due to an electron losing energy and changing orbits c. due to an interaction between electrons in two different principal orbits d. due to an electron gaining energy and changing orbits e. due to an increase in the principal quantum number n of an electron 10. What is the wavelength, in nm, associated with a 2000. kg truck traveling at a speed of 20 m/s, that is, considering the truck to be a "matter" wave? -29 A) 1.33 × 10 nm -29 B) 2.65 × 10 nm -29 C) 6.02 × 10 nm 3 D) 7.50 × 10 nm -29 E) 1.66 × 10 nm 11. An atomic orbital: I) describes a region of high electron density. II) describes a region in an atom where an electron is likely to be found. III) is a wave function resulting from specific values assigned to quantum numbers in wave equations. IV) describes a spherical region around a nucleus where an electron can be found. a. II only b. I and II c. II and III d. I, II, and III e. all are true 12. The possible values of the magnetic quantum number, mℓ , of a 3p electron are: a) 0, 1, 2 b) 2, 1, 0, -1, -2 c) 0 d) -1, 0, +1 e) +1, -1 3 13. To what uncertainty, in pm, can the position of an electron traveling at 1.89 × 105 m/s be measured if the uncertainty of the speed is 2.00%? a) 765 b) 654 4 c) 8.33 × 10 5 d) 1.53 × 10 4 e) 1.53 × 10 14. Which of the following have their valence electrons in the same shell? A) Li, N, F B) B, Si, As C) N, As, Bi D) He, Ne, F 15. If 1.00 g of an unknown molecular compound contains 8.35 x 1021 molecules, what is its molar mass? a. 44.0 g/mol b. 66.4 g/mol c. 72.1 g/mol d. 98.1 g/mol e. 132 g/mol 4  Part II: Short Answer Questions 16. [6 points] Periodic trends: 3+ + 3- a. Circle the species (atom/ion) that has the largest radius? Cl- Ar Sc K P b. Circle the element likely to have the largest second ionization energy: Na Mg Al Si 17. [8 points] Fill in the blanks: a. Assuming complete shielding by the core electrons, the effective nuclear charge for the valence electron/s in an atom of sodium is_____________ b. Use the basic rules for electron configuration to indicate the number of unpaired electrons in phosphorus. _____________________ c. The correct electron configuration for Br− is ______________________________. 192 d. The total number of neutrons in an Ir2+ is ________. 18. [5 points] List in order of increasing atomic size: F, Na, K, Mg, Ne. 19. [12 points] Please provide all quantum numbers required to specify each shell, subshell, or atomic orbital listed below. If the given shell, subshell, or atomic orbital does not exist, then please write ‘N/A’ in the ‘n’ column and leave the remaining ‘l’ and ‘ml’ spaces blank. (Hint: If a specific orientation is specified, only include 1 value of the orientation-specific quantum number. If no orientation is specified, then provide all possible values!) n l ml 𝟒𝒑 𝟓𝒇 𝟏𝟎𝒅𝒛𝟐 𝟑𝒅 5 Part III. Problems 20. [12 points] An electron bound to a hydrogenic atom undergoes a transition between a 2nd- and 4th-shell orbital. Radial distribution functions for these orbitals are given below, with the direction of the arrow denoting the direction of the electron’s transition. (a) Estimate the value of the most probable radius and most probable point (as appropriate for the information given by the plots above) for finding an electron in each orbital and identify the orbital. If multiple orientations are possible for the orbital, then select the orbital where at least one set of lobes are aligned along the x-axis. Lastly, please indicate the total number of radial and angular nodes for each orbital. Initial Wavefunction Final Wavefunction Orbital Number of radial nodes Number of angular nodes 23 [12 points] 14 karat (K) gold contains 58% Au by weight. a. How many moles of Au are found in a cube of 14K gold that is 0.660 mm on each side? Assume the density of 14K gold is 14.0 g/mL. b. How many atoms of gold in the 14K gold cube? 6 The blank pages that follow are for your own use -notes, calculations, etc- and will not be graded. You can also rip them off the exam and use them as scrap paper. If any of your final answers must written on the blank pages page, you must indicate so (including page #) under the relevant question/problem 7  USEFUL INFORMATION Metric conversions USEFUL EQUATIONS 5 ℎ 𝑅𝐻 𝐶 = (𝐹 − 32) KE = ½m2 𝜆= 𝐸𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 = −𝑍 2 9 𝑚𝑣 𝑛2 q1 q2 𝑐 1 1 K = C + 273.15 E=k 𝐸 = ℎ = ℎ 𝛥𝐸 = 𝐸𝑓 − 𝐸𝑖 = 𝑍 2 𝑅𝐻 ( 2 − 2 ) 𝑛𝑖 𝑛𝑓 r 𝜆 k= 8.99𝑥10 𝐽 ∙ 9 ℎ ∆𝑥(𝑚∆𝑣) = RH = 2.179  10 −18 J 𝑚/𝐶 2 4𝜋 8 9 10