The University of Sydney

Size: px

Start display at page:

Download "The University of Sydney"

Doreen Briggs
5 years ago
Views:

1 The University of Sydney SUPPLMNTRY OURS XMINTION /2005 GIV TH FOLLOWING INFORMTION IN LOK LTTRS FMILY NM OTHR NMS SI NUMR e-mil RSS (Use block letters) T The following examination is OPN OOK - you may use any reference sources and materials that you like, however, all the work presented must be your own. There is no time limit. When you have completed the paper, sign and date the declaration below, then submit it to the First Year nquiry Office at the School of hemistry between the hours of 0.00 am and 3.00 pm. Pages Max Gained Total 50 heck Total I declare that all of the work contained within is my own and that I have received no direct help from any person in the completion of this examination paper. Signed ate.

2 Supplementary ourse xamination Page of 8 pages ecember February 2005 The answers to the following 3 multiple choice questions should be indicated by clearly circling the letter next to the choice you make. ach question is worth mark. There is only one correct choice for each question. Negative marks will not be awarded for any question.. Which one of the following sets of quantum numbers is valid? n l m l s ½ ½ 3 0 +½ +½ 2 2 ½ 2. How many protons (p), neutrons (n) and electrons (e) are present in the 99 molybdenum isotope? 42 Mo 42 p 99 n 42 e 42 p 57 n 42 e 99 p 42 n 42 e 57 p 42 n 57 e 42 p 57 n 99 e 3. Which one of the following best describes the term nuclide? n atomic species distinguished by the composition of its nucleus. substituent particle of a nucleus. n energetic daughter product of a nuclear reaction. n atomic species distinguished only by the number of neutrons in its nucleus. n atomic species distinguished only by the charge of the nucleus. 4. Which one of the following statements concerning radioactive decay is true? The half-life of a radioactive isotope depends on the amount of radioactive material present. The activity of a radioactive isotope is inversely proportional to its decay constant. The half-life increases as more of the isotope decays. The activity of a radioactive isotope decays hyperbolically with time. The half-life is inversely proportional to the decay constant.

Supplementary ourse xamination Page 2 of 8 pages ecember 2004 - February 2005 5.

the wavefunction the square of the wave function the de roglie wavelength the reciprocal of the de

Which one of the following best describes an electronic wavefunction?

3 Supplementary ourse xamination Page 2 of 8 pages ecember February Which one of the following nuclides, with their decay processes given, could not be used for medical imaging? O 5 8 N e x-ray Ga 0 e 67 Zn m + γ Tc 99 Tc α Fr 20 t F 8 9 O e 6. Which of the following quantities is proportional to the electron density at a point? the wavefunction the square of the wave function the de roglie wavelength the reciprocal of the de roglie wavelength the Rydberg constant 7. Which one of the following best describes an electronic wavefunction? function of time describing radioactive decay. The set of solutions to the Schrödinger equation. function describing a wave in space that describes an electron. The function that describes molecular vibrations in time as a waving motion. The function describing the classical planetary orbit of an electron. 8. Which of the following is a lobe representation of a σ-bonding molecular orbital?

4 Supplementary ourse xamination Page 3 of 8 pages ecember February For which one of the following species is it possible to solve the wave equation analytically and obtain an equation for its electronic energy levels? He Li 2+ H 2 H He 0. Which of the following best describes Hund s rule? When atomic orbitals of equal energy are filled, the ground state electronic configuration is that with the most unoccupied orbitals. tomic orbitals should be filled from the lowest energy to the highest energy. When atomic orbitals of equal energy are filled, the ground state electronic configuration is that with the most unpaired electrons. lectrons in the same orbital must not have the same spin. nti-bonding orbitals possess a node between nuclei.. Which of the following best describes a 3p atomic orbital? function with 2 spherical nodes and planar node. function with spherical node and planar node. function with 2 spherical nodes and 2 planar nodes. function with 3 spherical nodes and 0 planar node. function with 3 spherical nodes and planar node. 2. Which one of the following diagrams best represents an n-type semi-conductor? (ark grey denotes filled electron energy levels, light grey denotes unfilled levels.) nergy 3. Which of the following best describes a p-type semiconductor? material with electrons in donor levels which may be thermally promoted to the conduction band. material with no band gap which conducts with little resistance. material with a sizeable band gap. material with empty acceptor levels to which electrons from the valence band may be thermally promoted. material with a very small intrinsic band gap.

5 Supplementary ourse xamination Page 4 of 8 pages ecember February 2005 In the spaces provided, explain the meaning of the following terms. You may use an example or diagram where appropriate. 6 (a) Pauli exclusion principle (b) conductance band (c) ionisation energy alculate the atomic mass of silicon from the isotope information provided. 2 Isotope Mass of isotope (a.m.u.) Relative abundance 28 Si % 29 Si % 30 Si % nswer:

6 Supplementary ourse xamination Page 5 of 8 pages ecember February 2005 alance the following nuclear reactions by identifying the missing nuclear particle or nuclide Fe 0 e 26-2 H + H 3 He 2 + N 7 + p 5 5 O 8 + alculate the molar activity of 3 H (in curie), given its half-life of 2.26 years. 3 nswer: The half life of 3 I is 8.06 days. alculate the activity, in q, of 2.0 g of pure 3 I. alculate the specific activity of 3 I in i mol. 3 nswer: q nswer: i mol

7 Supplementary ourse xamination Page 6 of 8 pages ecember February 2005 The ground state electron configuration of a sodium atom is [Ne] 3s and that of its first excited state is [Ne] 3s 0 3p. The intense yellow light (wavelength 590 nm) from a sodium street lamp arises when an electron drops from the first excited state to the ground state. alculate the energy associated with one photon of this yellow light. 4 nswer: The ionisation energy of ground state sodium is J per atom. alculate the energy required to ionise the 3p electron of an excited sodium atom. Give your answer in kj mol. nswer: Sketch the following wave functions as lobe representations. (a) a 2p atomic orbital (b) a π* molecular orbital 2

8 Supplementary ourse xamination Page 7 of 8 pages ecember February 2005 escribe how one of the following pieces of experimental evidence contributed to the development of quantum mechanics. photoelectric effect OR visible spectrum of hydrogen 3 Write down the ground state electron configurations of the following elements. Phosphorus is given as an example. 2 P s 2 2s 2 2p 6 3s 2 3p 3 Se K-shell x-ray emission (2p s) from an unknown element is of the same wavelength as the shortest x-rays observed as remsstrahlung when electrons are accelerated by 52.9 kev into a copper target. What is the name of the unknown element? 4 nswer:

9 Supplementary ourse xamination Page 8 of 8 pages ecember February is a reaction intermediate observed in flames, comets and circumstellar shells. 5 How many valence electrons are there in 2? omplete the calculated MO diagram for the ground state of 2 by inserting the appropriate number of valence electrons into the appropriate orbitals. energy (ev) σ π σ σ π -30 σ What is the bond order of 2? What is the longest wavelength of light that the ground state 2 + ion will absorb? Show working. nswer: THIS IS TH N OF TH XMINTION PPR.

Sample Exercise 6.1 Concepts of Wavelength and Frequency

Sample Exercise 6.1 Concepts of Wavelength and Frequency Two electromagnetic waves are represented in the margin. (a) Which wave has the higher frequency? (b) If one wave represents visible light and the