Exam 2-solutions

Exam 2-solutions - Version 292 – Exam 2 – mccord –...

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Unformatted text preview: Version 292 – Exam 2 – mccord – (51600) 1 This print-out should have 35 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 3.0 points Which of the following is the best represen- tation of the compound potassium sulfide? 1. None is appropriate because potassium sulfide is a covalent compound. 2. K 2+ , bracketleftbigg S b b b b b b b b bracketrightbigg 2 − 3. 2 K + , bracketleftbigg S b b b b b b b b bracketrightbigg 2 − correct 4. K 2+ , 2 bracketleftbigg S b b b b b b b b bracketrightbigg − 5. 3 K 2+ , 2 bracketleftbigg S b b b b b b b b bracketrightbigg 3 − 6. K + , bracketleftbigg S b b b b b b b b bracketrightbigg − Explanation: The best drawing will show the valence elec- trons, the charges, and the appropriate ratio of ions for K 2 S. 002 3.0 points Which of the following best describes the range of atomic radii? 1. 10 to 30 ˚ A 2. 1 to 100 ˚ A 3. 5 to 10 ˚ A 4. 0.05 to 1 ˚ A 5. 1 to 15 ˚ A 6. 0.4 to 3 ˚ A correct Explanation: Atomic radii vary from 30 pm (He) to 300 pm (Fr). 1 ˚ A= 10 − 10 m = 100 pm, so the range of atomic radii is 0.3 to 3 ˚ A. 003 3.0 points How many resonance forms are possible for the ethanoate ion? The formula for the ethanoate ion is CH 3 COO − . 1. 5 2. 1 3. 4 4. 2 correct 5. 3 Explanation: The Lewis structures are C O b b b b b b H 3 C O b b b b − ↔ C O b b b b b b H 3 C O b b b b − 004 3.0 points Given the elements Cl, Ge, and K and the values 418, 1255, and 784 kJ/mol of possible first ionization energies, match the atoms with their first ionization energies. 1. Cl: 418 kJ / mol, Ge: 1255 kJ / mol; and K: 784 kJ / mol 2. Cl: 1255 kJ / mol; Ge: 418 kJ / mol; and K: 784 kJ / mol 3. Cl: 1255 kJ / mol; Ge: 784 kJ / mol; and K: 418 kJ / mol correct 4. Cl: 418 kJ / mol; Ge: 784 kJ / mol; and K: 1255 kJ / mol 5. Cl: 784 kJ / mol; Ge: 1255 kJ / mol; and K: 418 kJ / mol Explanation: Cl is a Group 7 non-metal and will tend to form a- 1 ion, so it will be very reluctant Version 292 – Exam 2 – mccord – (51600) 2 to give up an electron and will have a very high first ionization energy. K is a group 1 metal and will readily lose an electron to form a +1 ion so the first ionization energy will be very low. Ge will form positive ions and be intermediate in its first ionization energy. 005 3.0 points The electronic arrangment is the same as the molecular shape when 1. the number of bonding orbitals equals the number of anti-bonding orbitals. 2. the atoms are joined by sigma bonds. 3. there are more shared electrons than non- shared electrons....
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This note was uploaded on 05/12/2011 for the course CH 301 taught by Professor Fakhreddine/lyon during the Spring '07 term at University of Texas.

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Exam 2-solutions - Version 292 – Exam 2 – mccord –...

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