CHEM 1110 Principles of Chemistry I Sample Exam 2 Fall 2024 PDF

CHEM:1110 Principles of Chemistry I - Sample Exam 2 - Fall 24 Name___________________________________ MULTIPLE CHOICE. Choose the one item that best completes the statement or answers the question. 1) Bioluminecence is the emission of light by a living organism. Fireflies (lightning bugs)...

CHEM:1110 Principles of Chemistry I - Sample Exam 2 - Fall 24 Name___________________________________ MULTIPLE CHOICE. Choose the one item that best completes the statement or answers the question. 1) Bioluminecence is the emission of light by a living organism. Fireflies (lightning bugs) emit light from an excited state of the molecule oxyluciferin. The fluorescence emission spectrum for oxyluciferin is shown. Based on this emission spectrum, what color light will the human eye see emitted? A) red B) orange C) yellow D) green E) blue 1 2) Energy levels (shells) n = 1, n = 2, n = 3, and n = 4 for a molecule are shown. A sample of the molecule is irradiated with light at frequencies A, B, C, and D. Light is absorbed and the energy promotes transitions between the energy levels. Match the frequencies with the transitions between the shells. A) n = 1 to n = 4 D n = 1 to n = 3 A n = 1 to n = 2 B n = 1 to n = 1 C B) n = 1 to n = 4 C n = 1 to n = 3 B n = 1 to n = 2 A n = 1 to n = 1 D C) n = 1 to n = 4 A n = 1 to n = 3 B n = 1 to n = 2 C n = 1 to n = 1 D D) n = 1 to n = 4 B n = 1 to n = 3 C n = 1 to n = 2 A n = 1 to n = 1 D E) n = 1 to n = 4 D n = 1 to n = 3 C n = 1 to n = 2 B n = 1 to n = 1 A 2 3) Vitamin D is made in the skin on absorption of sunlight. What is the frequency of 303 nm photons? A) 9.09 x 1010 s-1 B) 1.0 x 1011 s-1 C) 9.90 x 1014 s-1 D) 9.09 x 101 s-1 E) 9.90 x 105 s-1 4) An electron cloud (gray oval) with two nuclei (white circles) and four electrons (dark circles) is sketched. Consider the following statements and identify the statement that is not correct. (a) Two electrons form one bond. In this sketch, two bonds form. (b) Electrostatic repulsion between the electrons is small because the electrons are far apart in the electron cloud. (c) The strongest attractive potential energy is between the four electrons and the two nuclei that forms the bond. (d) The precise location of the electrons is shown by the dark circles. (e) The electron cloud (gray oval) represents the greatest probability of where the electrons are located. A) (a) B) (b) C) (c) D) (d) E) (e) 3 5) The 2pz orbital shown below comes from the quantum mechanical model for an atom. Which of the following statements is not consistent with this model for an atom? A) There are two additional p orbitals in the second electron shell aligned in the x and y directions. B) We cannot measure the exact location and speed of an electron simultaneously. C) An electron in the 2pz orbital has higher energy than one in the 2s orbital. D) Electrons move around the nucleus in circles with fixed radii. E) The 2pz orbital can accommodate at most two electrons. 6) The radii of atoms vary across and down the periodic table. Consider the following elements. Mg B O Sr Order the elements from smallest to largest radius. A) B < O < Mg < Sr B) O < B < Mg < Sr C) O < Mg < B < Sr D) Sr < Mg < B < O E) Mg < O < B < Sr 4 7) The electron configuration for phosphorus P identifies that photoelectron spectroscopy (PES) will find the lowest energy electrons are in the 3p orbitals. What is the electron configuration for phosphorus? A) [Ne]3s13p4 B) [Ne]3p5 C) 1s22s22p63s23p6 D) 1s22s22p63s23p2 E) 1s22s22p63s23p3 8) What is the electron configuration of the Br3+ ion? A) [Ar]4s23d104p2 2 10 6 B) [Ar]4s 3d 4p C) [Ar]4s23d105s2 D) [Kr]5s2 E) [Ar]4s23d104p8 5  9) Photoelectron spectroscopy measures the ionization energy of all electrons in a sample. The photoelectron spectrum for an elemental sample is shown. What is the first ionization energy in MJ/mol and what is the element? A) 347, K B) 347, Na C) 0.42, K D) 347, Rb E) 0.42, Rb 10) In the periodic table, the 3d metals lie between scandium (Sc, Z = 21) and zinc (Zn, Z = 30). How many d-orbitals are in 3d metals? A) 1 B) 2 C) 5 D) 6 E) 10 6  11) Potential energy of bond formation varies with distance between the two nuclei as shown in the chart below. Which statement below correctly describes bond formation? A) When the potential energy is most negative because there are only attractive electrostatic interactions between the electrons and nuclei B) When the potential energy is most negative because attractive electrostatic interactions between the electrons and nuclei and repulsive interactions between the nuclei-nuclei and between electron-electron balance C) When the atoms are sufficiently well separated that all electrostatic interactions are minimized D) When interatomic distance is shortest because this maximizes overlap in the electron cloud and maximizes the potential energy E) The potential energy plot shows that no bonds are formed. 12) Hydrogen cyanide is a toxic gas that smells of bitter almonds. What is the molecular geometry of HCN? A) bent B) trigonal planar C) linear D) tetrahedral E) trigonal pyramidal 7 13) Urea, also known as carbamide, has molecular formula CH4N2O. From mass spectrometry (MS), the molar mass is 60.06 g mol-1. Which molecular structure best fits the IR spectrum below? A) B) C) D) 8 14) Dopamine is a neurotransmitter. Select the list of functional groups contained in dopamine. A) phenyl, aldehyde, alcohol B) alcohol, phenyl, amine C) amine, carboxylic acid, aldehyde D) carboxylic acid, amine, alcohol E) amine, ether, phenyl 15) How many resonance structures are there for nitrate anion NO3-? A) zero B) one C) two D) three E) four 16) Which of the following statetments are true about the C-O bond in the carbonate ion CO32-? I. There are multiple resonance structures for CO32-. II. The C-O bond in CO32- is longer than a double bond and shorter than a single bond. III. The C-O bond in CO32- is stronger than a single bond and weaker than a double bond. IV. The C-O bond in CO32- is constantly changing between a single bond and a double bond due to resonances. V. The three C-O bonds in CO32- have different lengths. A) I, II, III, IV and V B) I, II, III, and IV only C) I, II and III only D) I and V only E) V only 9 17) Air is about 76 % nitrogen by mass. Nitrogen is nonreactive because the triple bond in N2 is not easily broken. The bond energy of the N2 triple bond is 945 kJ mol-1. What is the correspondin g wavelength (nm) of a photon with enough energy to break one N 2 bond? A) 0.157 nm B) 1.27 x 10-4 nm C) 9.45 x 105 nm D) 127 nm E) 1.27 x 105 nm 18) What is the molecular geometry of the hydronium ion H3O + ? A) trigonal pyramid B) trigonal planar C) bent D) linear E) tetrahedral 19) What is the bond angle in SiH4 ? A) 109.5 ° B) 180.0 ° C) < 190 ° D) 90.0 ° E) 120.0 ° 10 20) A student carried out a complexometric titration to determine the hardness (expressed in ppm of CaCO3) of the tap water in the lab. The student used 0.00480 M EDTA solution to titrate 50.0 mL of the tap water. Based on the data recorded below, what is the volume of EDTA solution used to reach the equivalence point? (density of tap water = 1.00 g/mL; molar mol mass of CaCO3 = 100. g/mol; M = ) L Moles of CaCO3 in 50 mL water sample = 4.05 x 10- 5 Tap water hardness in ppm of CaCO3 = 81.0 A) 2.03 mL B) 4.22 mL C) 4.80 mL D) 8.44 mL E) 12.6 mL 21) Which of the following molecules cannot absorb infrared (IR) radiation and why? CO2, N2, H2O, CF4 A) CO2, because double bonds do not absorb in the IR region. B) N2, because the dipole moment of the molecule does not change during its vibration. C) H2O, because the dipole moment of the molecule does not change during any of its vibrations. D) CF4, becauseCF4 is a nonpolar molecule. E) CO2, because the dipole moment of the molecule does not change during any of its vibrations. 11 22) Which bond in the lanthionine molecule is the most polar? A) C-O bond B) O-H bond C) C-C bond D) N-H bond E) C-N bond 23) Rank the polarities of the following molecules: HF, HCl, HBr, and HI. A) HBr > HI > HCl > HF B) HI = HBr = HCl = HF C) HF > HCl > HBr > HI D) HI > HBr > HCl > HF E) All molecules are nonpolar. 24) Which of the following molecules is a nonpolar molecule? A) B) 12  C) D) E) 25) How many moles of OH- are in a 0.62M NaOH solution with a volume of 8 µL? A) 5.0 x10-6 moles OH- B) 7.8 x10-2 moles OH- C) 5.0 x106 moles OH- D) 1.3 x102 moles OH- 13 Answer Key Testname: CHEM1110_F23_SAMPLE EXAM 2 V2 1) E 2) B 3) C 4) D 5) D 6) B 7) E 8) A 9) C 10) C 11) B 12) C 13) C 14) B 15) D 16) C 17) D 18) A 19) A 20) D 21) B 22) B 23) C 24) D 25) A 14 Clearly Print your name (as it appears in MyUI) and your ID number: Full Name as it appears on MyUI:__________________________________ ID#_________________________ Chem 1110 – Principles of Chemistry I Sample Exam #2: Free Response Write your answers in the spaces provided on the front side only. Please write clearly and neatly. 23) Many compounds are found on human breath. The empirical formula of the most common is C5H8. Mass spectrometry (MS) and infrared spectroscopy (IR) spectra are shown. Other types of spectroscopy determine that one carbon is bonded to three carbons but no hydrogens. A) Identify a compound consistent with the data. Draw the structure in the box showing all atoms, bonds and lone pairs (if any). B) Explain your reasoning to determine the structure. Frame your answer in terms of the available spectroscopy data. Be clear and specific. Please print clearly. Writing on the back will not be graded.