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exam 1 jrs

exam 1 jrs - Version 106 Exam One Shear Shear(52375 This...

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Version 106 – Exam One: Shear – Shear – (52375) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points In general, atomic size tends to increase 1. from bottom to top and from left to right on the periodic table. 2. from bottom to top and from right to left on the periodic table. 3. There is no relationship between the size of an atom and its position on the periodic table. 4. from top to bottom and from right to left on the periodic table. correct 5. from top to bottom and from left to right on the periodic table. Explanation: Atomic sizes are largest in the bottom left- hand corner and smallest in the top right-hand corner of the periodic table. 002 12.0 points The molecular formula for ethyl chloride (C 2 H 5 Cl). What is the molecular weight of ethyl chloride? 1. 34.0 grams/mol 2. 8 grams/mol 3. 69.5 grams/mol 4. 64.5 grams/mol correct 5. 48.5 grams/mol Explanation: The formula weight of a compound is based on the atomic weights of the elements in the compound. Each mole of C 2 H 5 Cl contains 2 mol of C, 5 mol of H, and 1 mol of Cl. We know the atomic masses of each of these elements from the periodic table. Using these atomic masses we calculate the grams of each of these elements in one mole of C 2 H 5 Cl: m C = 2 mol C × 12 . 01 g C 1 mol C = 24 . 02 g C m H = 5 mol H × 1 . 01 g H 1 mol H = 5 . 05 g H m Cl = 1 mol Cl × 35 . 45 g Cl 1 mol Cl = 35 . 45 g Cl To get the mass of one mole of C 2 H 5 Cl we add the masses of the component parts. This is the formula weight: FW C 2 H 5 Cl = 24 . 02 g + 5 . 05 g + 35 . 45 g = 64 . 52 g C 2 H 5 Cl mol C 2 H 5 Cl 003 10.0 points The ground state electron configuration of the silver atom is [Kr] 5 s 1 4 d 10 instead of [Kr] 5 s 2 4 d 9 . The observation can be explained (theoretically) by the fact that 1. an enhanced stability is associated with filled sets of equivalent orbitals. correct 2. the 4 d subenergy level has higher energy than the 5 s subenergy level. 3. the 4 d subenergy level always has 10 elec- trons. 4. only one electron can occupy a 5 s or- bital. 5. the magnetism measurement shows one unpaired electron. Explanation: 004 10.0 points Which of the following is a chemical property of sulfur? 1. density of 2.07 g/ml

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Version 106 – Exam One: Shear – Shear – (52375) 2 2. melts at 119 C 3. burns in air correct 4. dissolves in carbon disulfide Explanation: Burning in air as opposed to melting or dis- solving shows a change it undergoes in chem- ical composition. Melting and dissolving are physical properties not chemical. 005 10.0 points The number of unpaired electrons in a neutral atom of titanium (Ti) is 1. 1. 2. 2. correct 3. 3. 4. none 5. 4. Explanation: Titanium’s electronic configuration is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 2 All of the orbitals before 3 d are completely filled, so no unpaired electrons exist in them.
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