Final-70x-solutions

Final-70x-solutions - Version 280 – Final-70x – mccord...

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Unformatted text preview: Version 280 – Final-70x – mccord – (50970) 1 This print-out should have 51 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points 1 s 2 2 s 2 2 p 6 3 s 2 3 p 5 is the electron configura- tion for which one of the following ions? 1. P 2+ 2. Cl − 3. P + 4. S + 5. P 2 − correct Explanation: We need an ion that has 2 + 2 + 6 + 2 + 5 electrons; i.e. , P 2 − . 002 10.0 points What would be the signs of Δ H and Δ S for the reaction AB 4 (g) → AB 3 (g) + B(g)? 1. Δ H = +, Δ S = 0 2. Impossible to tell from the information given. 3. Δ H = +, Δ S =- 4. Both negative. 5. Both zero. 6. Both positive. correct 7. Δ H = 0, Δ S = + 8. Δ H =- , Δ S = 0 9. Δ H =- , Δ S = + 10. Δ H = 0, Δ S =- Explanation: Δ H is positive (endothermic, net bond breaking). Δ S is also positive because the random- ness of the system has increased. (1 mole of gaseous reactants forms 2 moles of gaseous products.) 003 10.0 points For a Bohr atom, which of the following tran- sitions emits the highest energy photon? 1. from n = 6 to n = 5 2. from n = 4 to n = 3 3. from n = 2 to n = 1 correct 4. from n = 10 to n = 8 Explanation: Energy levels decrease in energy and get closer together in energy as they move away from the nucleus, so the two energy levels with the largest energy and greatest energy difference will be the two lowest energy levels in the list. 004 10.0 points Which of the following gases will have the largest root mean square speed at 100 ◦ C? 1. argon 2. methane correct 3. water 4. oxygen 5. nitrogen Explanation: Rate of effusion ∝ 1 √ MW MW’s for each gas: H 2 O : 18 . 0152 g / mol; Ar : 39 . 948 g / mol; CH 4 : 16 . 0426 g / mol; O 2 : 31 . 9988 g / mol; N 2 : 28 . 0134 g / mol . Version 280 – Final-70x – mccord – (50970) 2 The lightest gas will have particles moving at the highest average speed. 005 10.0 points Visible light, microwaves, and x-rays travel through empty space at 3.00 × 10 8 m · s − 1 . 1. True correct 2. False Explanation: All forms of electromagnetic radiation move at the same speed through empty space, at speed c = 3 × 10 8 m/s. 006 10.0 points Which of the following are forces between molecules? 1. translational forces 2. intermolecular forces correct 3. extra-terrestial forces 4. co-molecular forces 5. intramolecular forces 6. van Halen forces Explanation: Inter molecular forces are those that act be- tween molecules. Intra molecular forces occur within molecules. 007 10.0 points Which of the following elements would be expected to have the lowest first ionization energy? 1. K 2. Ca 3. Rb correct 4. O 5. Mn Explanation: Ionization energy decreases going down the Periodic Table....
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Final-70x-solutions - Version 280 – Final-70x – mccord...

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