2009 Midterm - Chemistry 1024b Winter 2009 Midterm Exam...

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Chemistry 1024b, Winter 2009 Midterm Exam with Solutions Page 1 out of 9 1. What is the name of the compound with the formula NaClO 2 ? A) sodium hypochlorite; B) sodium chloride; C) sodium chlorite; D) sodium chlorate; E) sodium perchlorate. 2. What is the name of the compound with the formula N 2 O 4 ? A) nitric oxide; B) nitrous oxide; C) nitrogen dioxide; D) dinitrogen tetraoxide; E) nitrogen peroxide. 3. What is the chemical formula of iron (III) nitrate? A) Fe(NO 3 ) 2 ; B) Fe(NO 3 ) 3 ; C) Fe 2 (NO 3 ) 3 ; D) Fe(NO 2 ) 3 , E) Fe 2 (NO 2 ) 3 . 4. What is the number of neutrons in one atom of 58 Ni? A) 20; B) 30; C) 40; D) 58; E) 0. The mass number of 58 Ni is 58. The number of protons is 28 because the atomic number of Ni is 28. The nucleus contains of protons and neutrons. The number of neutrons is the total number of neutrons and protons minus the number of protons, or 58 - 28 = 30. 5. According to the periodic table, element chlorine has the atomic mass of 35.45 atomic mass units. What does it mean? A) one atom of chlorine has 18.45 neutrons; B) one atom of chlorine has 35.45 neutrons; C) one atom of chlorine has 19 neutrons and 17 protons but because of the mass defect the atomic mass of chlorine is 35.45; D) one atom of chlorine has 18 neutrons and 17 protons but because of the mass defect the atomic mass of chlorine is 35.45; E) there are several stable isotopes of chlorine, so an average atom of chlorine weighs 35.45 atomic mass units. 6. What is the number of electrons in the most abundant ion of potassium? A) 18; B) 19; C) 20; D) 39; E) 39.10. Potassium is in Group 1 of the periodic table. Elements of Group 1 form only single-charged positive ions, that is how they achieve the most stable electronic configuration of a nearest noble gas. The atomic number of potassium is 19, this means a neutral atom of potassium has 19 electrons. A single-charged positive ion has one electron less, that is, 18.
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Chemistry 1024b, Winter 2009 Midterm Exam with Solutions Page 2 out of 9 7. Indicate which of the following statements is correct: A) All isotopes of the same element have the same chemical properties; B) All isotopes of the same element have the same chemical properties; however, different isotopes of the same element may have slightly different chemical reactivities; C) Different isotopes of the same element have totally different chemical properties; D) All isotopes of the same element have the same chemical properties except those which are unstable. The unstable and stable isotopes have different chemical properties. E) Different isotopes of the same element may have different chemical properties; however, this is true only for heavy elements. 8. What is the mass of sulfur dioxide SO 2 that contains the same number of sulfur atoms as 24.00 g of iron (II) disulfide FeS 2 ? A) 12.81 g; B) 25.63 g; C) 51.26 g; D) 19.22 g; E) 38.44 g. The molecular mass of iron (II) disulfide is 119.99 amu, the molecular mass of sulfur dioxide is 64.07 amu. 24.00 g of it correspond to 24.00/119.99 = 0.2000 moles (4 significant figures).
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