CHEM 6A Lecture 14: CHEM W5 Lec 11/1/17

provided to determine AH rxn for the following reaction: urf (klimol) CH4(g) + 3 Cl2(g) → CHCI3() + 3 HCI(g) airrxn-? A)-151 kJ B)33SkJ C) +662kJ D) +117kJ E)-217 kJ A) 4.1 atm B) 5.0 atm c) 6.4 atm D)1.1 atm E) 2.3 atm kg) of the copper sample if the specific heat capacity of copper is 0 CH4(g) 75 CHCI3() -134 HCI(g) -92 8) What pressure will 14.0 g of CO exert in a 3.5 L container at 75 C? 9) A sample of copper absorbs 43.6 kJ of heat, resulting in a temperature rise of 50.0°C, determine the mass (in .385 J/g C A) 226 kg B) 0.235 kg C)6.64 kg D) 119kg E)5.10 kg 10) Which of the following processes is exothermic? A) the ionization of a melting snow atom B) the breaking of a boiling of water bond C) the boiling of water D) the condensation of water E) All of the above processes are exothermic 11) Calculate the energy of the red light emitted by a neon atom with a wavelength of 703.2 nm. B)4.27 x 10-19J C) 2.34 x 10-19J D)6.45 x 10-19J E) 2.83 x 10-19J A)3.54 × 10-19J 12) Identify the color of a flame test for potassium D) yellow A) violet B) red C) white E) blue 13) Which of the following statements is TRUE? A) The emission spectrum of a particular element is always the same and can be used to identify the element. B) Part of the Bohr model proposed that electrons in the hydrogen atom are located in "stationary states" or particular orbits around the nucleus. C) The uncertainty principle states that we can never know both the exact location and speed of an electron. D) An orbital is the volume in which we are most likely to find an electron. E) All of the above are true. 14) Calculate the wavelength of an electron (m-9.11 x 10-28 g) moving at 3.66 × 106 m/s. A)1.99 x 10-10m B)5.03 x 10-10 m C) 1.81×10-10 m D)5.52 × 10-9 m E) 2.76 × 10-9 m 15) Which of the following quantum numbers describes the shape of an orbital? A) principal quantum number B) magnetic quantum number C) spin quantum number D) Schrödinger quantum number E) angular momentum quantum number 16) Determine the energy change associated with the transition from n = 2 to n-5 in the hydrogen atom. A)-218×10-19J B)+654 × 10-19 J C) +4.58 x 10-19 J D)-1.53 x 10-19 J E) +3.76 × 10-19J 17) If two electrons in the same atom have the same value of I, they are A) in the same sublevel, but not necessarily in the same level. me level, but different sublevel. C) in the same orbital. D) in different levels and in different shaped orbitals. E) none of the above.

Physical Constants R-00821 L.atm rnol. K: 1 atm = 760 Torr; h-6626 x 10". Js; c-3.00 x 10e mis Multiple Choice Question-4 points each. Circle the correct choice. 1. How many orbitals are there in the n - 3 shell? )3 b)6 )9 d) 12 e) none of the preceding choices 2. Which of the following is not a valid set of four quantum numbers to describe an electron in an atom? 3. Which pair of elements would you expect to exhibit the most similar physical and chemical properties? a) As and Se b) Na and Cl c) As and Sb d) B and Be 4) The number of unpaired electrons in the ground state of an atom of Co is.. (A) one (B) three (C) five (D) seven (E) none of the preceding choices S. Which of the following processes is exothermic? a) lonization of a sodium atom b) Formation of gaseous chlorine atoms from Cl, (g) c) Breaking apart of NaC1 (s) into ions d)Addition of an electron to a chlorine atom 6. Which of the following bonds is the most polar? a) N-O b)O-F e) B-O d)S-o e) all are equally polar At what temperature (in C) will 25.0 g of carbon dioxide (at 1,00 atm) occupy 21.5 L? 188°C b) 461°C c) -263°C d)-270°C e)113°C How many times more rapidly will hydrogen (H2) gas effuse through a pinhole than will deuterium (D ) gas? Deuterium is an isotope of hydrogen with a molecular mass of 4.0 g/mole. (A) V2 (B) 2 (C)2v2 (D) 4 9. Which of the following arrangements from lowest to highest in first ionization energies is correct ? 10. In which of the following compounds obeys the octet rule? 1. The bright spectral lines observed in the emission spectrum of a flame or gas discharge tube are due to a) XeF b) BF, c) Cio d) so e) none of the preceding choicees a) the absorption of light at specific wavelengths b) the formation of an excited state of atoms c) the transition of an atom from an excited state to a lower energy state d) the change from anti-parallel to parallel electron spins in an atom 2. A one-liter container is filled with one mole of hydrogen at 25 °C. A second one-liter container is filled with one mole f oxygen at 25 °C. Comparing the pressure of the hydrogen to the oxygen, the ratio will be Fro n Bond Dissociation Enthalpies: AHD (CI-CI)-243 kJrnolAMD (F-F )一159 klinol; lculate the enthalpy, AH, for the chemical reaction: Cl: (g)+F: (g) 2CIF(R) )-147 kJ (b)-108 kJ (c)+171 kJ (d) +912 k AHD (CI F)-255 kJ mol ;

Abstract This physical chemistry laboratory exercise will have students work with provided emission spectra for several elements and data collected on the NIST Atomic Spectral Database. First, students will develop a method for calculating what wavelengths of visible light are associated with the most intense spectral lines in the provided visible emission spectra. Then, the NIST Atomic Spectral Database will be accessed in order to identify select properties associated with the four most intense spectral lines. Introduction The emission process can be described in two general parts. Initially, energy is absorbed by an atom, and its electrons can be moved into higher energy (excited) states from their ground state The excitedrelectrons then "relax" and drop back to their ground state. Energy lost during an electron's retaxation process is emitted as a photon. Recall that the energy of a photon is photon upper E lower Where Ephoton is the energy of the photon that is emitted when the emitter drops from an upper energy state to a lower energy state, h is Planck's constant, c is the speed of light, and v is the wavenumber. Remember that the length units should match for c and v This is a good time to revisit a few concepts. Atoms and molecules possess discrete energy levels their energy levels are quantized and not continuous. Using eq 7.1, it is possible to determine the energy associated with a specific excited state to ground state transition if we can determine the wavelength of emitted light. Also keep in mind that there are selection rules that limit the type of transitions we can expect to observe. All of these points are reflected in an elemental or ionic emission spectrum. The visible light spectrum falls within a fairly narrow range of wavelengths, from approximately 400 to 700 nm. Even so, discrete spectral lines are seen in each element's visible light emission spectrum. Each (take some time to reflect on why that would be), each element also has a unique emission spectrum. This provides a diagnostic tool for determining the composition of a sample. As an example, the elements present in celestial objects can be determined by the light that they produce line represents one possible transition. Since each element has unique energy levels Some of the transitions observed in this lab exercise involve d-orbitals. As such, a discussion regarding d-orbitals and related selection rules is necessary at this point. The first goal is to determine which character table should be used. Start by observing the shape and relative orientations of the d-orbitals. Refer to Figure 1 below