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Midterm

2011+Nov Midterm Exam.pdf

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Department
Chemistry
Course
Chemistry 1027A/B
Professor
Tom Haffie
Semester
Fall

Description
Chemistry 1100A Test # 2 November 12, 2011 Code 000 Page 1 1. A natural sample of element X contains two isotopes, the masses of which are 68.95 amu and 70.95 amu. The average atomic mass of this element is 69.75 amu. What is the percentage abundance of each of the two isotopes? The lighter isotope is listed first. A) 60, 40 B) 52, 48 C) 30, 70 D) 56, 44 E) 70, 30 2. The molecule shown is acetylsalicylic acid. For a 100 g sample of acetylsalicylic acid, which one of the following statements is correct ? (NA = 6.02 x 10 ) A) The sample contains 35.5% oxygen by mass. B) The sample contains 21 moles of atoms. C) The sample contains 3.34 x 10 23atoms. D) The sample contains 3.33 moles of hydrogen atoms. E) The sample contains more oxygen than carbon by mass. 3. For the reaction: A + 2 B + 3 C 2 D 2.00 moles of A are reacted with 3.00 moles of B and 5.00 moles of C. After the reaction goes to completion, which one of the following statements is correct? A) One-half of a mole of C remains unreacted. B) One mole of A remains unreacted. C) No A remains unreacted. D) Two-thirds of a mole of B has reacted. E) One-third of a mole of C remains unreacted. Chemistry 1100A Test # 2 November 12, 2011 Code 000 Page 2 4. All of the chloride in an aqueous solution of CaCl2 was precipitated completely as AgCl. If 0.715 g of AgCl is obtained from 25.0 mL of aqueous CaCl , what was 2 the molarity of the CaCl2solution? A) 0.100 B) 0.0250 C) 0.0500 D) 0.200 E) 0.400 5. What is the pH of a solution prepared by mixing 100 mL of 0.250 M HNO 3 with 150 mL of 0.100 M Ba(OH) ? 2 A) 12.30 B) 11.70 C) 1.70 D) 2.00 E) 7.00 Chemistry 1100A Test # 2 November 12, 2011 Code 000 Page 3 6. Which one of the following sets of quantum numbers is correct for a ground state, valence shell electron in tin, Sn? A) n = 5, l = 1, m l= −1, m = s½ B) n = 5, l = 0, m = l, m = +½s C) n = 4, l = 1, m = l1, m = -½ s D) n = 4, l = 2, m = l, m = -½s E) n = 5, l = 0, m = l, m = +½s 7. Which of the following statements is/are correct for an atom of antimony, Sb, in the ground state? i) It has three unpaired electrons ii) The highest energy electron is in a 5p orbital iii) The highest energy electron could have a value of m l of −2 2+ iv) It is isoelectronic with In A) i) and ii) only B) i), ii) and iv) only C) ii) and iv) only D) iii) and iv) only E) i), iii) and iv) only Chemistry 1100A Test # 2 November 12, 2011 Code 000 Page 4 8. Which one of the following species in the ground state has the greatest number of unpaired electrons? A) Mn 2+ B) Fe 2+ 3+ C) Cr 2+ D) Co 2+ E) Zn 9. Based on periodic trends, how many of the following statements is/are correct? i) The correct order for decreasing atomic radius is Ca > Mg > Na. ii) The correct order for decreasing first ionization energies is Rb > K > Na. 2− 2− 2− iii) In the ground state, O , S and Se are isoelectronic with each other. iv) CaO has a higher melting point than MgO. A) 0 B) 1 C) 2 D) 3 E) 4 10. Which one of the following statements best explains why atomic oxygen has a lower first ionization energy than atomic nitrogen? A) Oxygen has a pair of electrons in one p orbital, resulting in repulsion. B) Oxygen has more electrons than nitrogen. C) Oxygen has a larger effective nuclear charge than nitrogen. D) Nitrogen has a triple bond, so it is harder to ionize than oxygen. E) Nitrogen must gain more electrons than oxygen to obtain a full octet. Chemistry 1100A Test # 2 November 12, 2011 Code 000 Page 5 − 11. Which of the following statements concerning nitrate ion, NO 3 , is/are correct? i) It has an average bond order of 5/3. − ii) The best Lewis structure of NO ,3has at least one O atom with a formal charge of −1. iii) Three equivalent resonance structures can be drawn. A) ii) and iii) only B) i) and iii) only C) All statements are correct D) i) and ii) only E) iii) only 12. Consider the Lewis structure show below. Which one of the following elements could X be? A) I B) Se C) F D) N E) Si Chemistry 1100ATest # 2 November 12, 2011 Code 000 Page 6 13. Whic− one of the following is the best Lewis structure for the thiocyanate ion, SCN ? A) B) S C N C) D) 2- S C N E) 2− 14. Consider the oxalate io2,4C , which has a C – C bond. Which of the following statements concerning the best Lewis structure for this ion is/are correct? i) Two oxygen atoms each have a formal charge of −1. ii) There are only two equivalent resonance structures. iii) The average bond order of each carbon-oxygen bond is 3/2. A) i) and iii) only B) ii) only C) iii) only D) i) and ii) only E) ii) and iii) only Chemistry 1100A Test # 2 November 12, 2011 Code 000 Page 7 2― 15. The ion XO4 has a see-saw molecular geometry. What is a possible identity of X? A) Kr B) S C) Ne D) Si E) Br 16. How many of the following molecules are polar? PO 43− TeF 4 CCl 4 BrF 5 CH 3CH 3 A) 3 B) 1 C) 2 D) 0 E) 4 17. Which one of the following molecules contains a bond angle of 90°? A) XeF 4 B) CF + 3 C) SF 4 D) H O + 3 E
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