Homework #1 Solutions

# Homework #1 Solutions - purdy(sbp456 Homework 1 owers(53885...

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purdy (sbp456) – Homework 1 – flowers – (53885) 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points The formation of tiny bubbles when a beaker of water is mildly heated indicates that 1. water is being decomposed into hydrogen and oxygen. 2. the liquid is at its boiling point. 3. air is less soluble in water at higher tem- peratures. correct 4. water is being extensively hydrogen bonded. 5. the lattice energy of water is large. Explanation: The bubbles are tiny pockets of air that were dissolved in the water at the lower tem- perature. As the gas molecules acquired more energy they were able to escape from the sol- vent. 002 10.0 points Calculate the concentration of argon in lake water at 20 C. The partial pressure of argon is 0.0090 atm and Henry’s constant is 0.0015 mol · L 1 · atm 1 . 1. 6.0 M 2. 1.4 × 10 5 M correct 3. 9.0 × 10 3 M 4. 0.17 M 5. 1.5 × 10 3 M Explanation: 003 10.0 points Based on the types and strengths of in- termolecular forces present, place the com- pounds C 6 H 14 , C 3 H 8 , C 5 H 11 OH , C 5 H 11 Cl , CaBr 2 in order from lowest to highest boiling point (lowest on the left, highest on the right). 1. C 6 H 14 , C 3 H 8 , C 5 H 11 OH , C 5 H 11 Cl , CaBr 2 2. CaBr 2 , C 5 H 11 Cl , C 6 H 14 , C 5 H 11 OH , C 3 H 8 3. CaBr 2 , C 5 H 11 OH , C 5 H 11 Cl , C 6 H 14 , C 3 H 8 4. C 3 H 8 , C 6 H 14 , C 5 H 11 OH , C 5 H 11 Cl , CaBr 2 5. C 3 H 8 , C 5 H 11 OH , C 6 H 14 , C 5 H 11 Cl , CaBr 2 6. C 3 H 8 , C 6 H 14 , C 5 H 11 Cl , C 5 H 11 OH , CaBr 2 correct Explanation: C 3 H 8 and C 6 H 14 have only dispersion forces, the weakest type of intermolecular forces. C 6 H 14 has a higher molecular weight and will therefore have stronger dispersion forces. C 4 H 11 Cl and C 5 H 11 OH are both approx- imately the same size as C 6 H 14 and would therefore have about the same strength of dis- persion forces. C 4 H 11 Cl also has dipole-dipole interactions, stronger than dispersion forces. C 5 H 11 OH also has H - bonding, stronger than dipole-dipole interactions. CaBr 2 is ionic and has interionic forces, the strongest type of intermolecular forces. The stronger the intermolecular forces, the higher the boiling point. 004 10.0 points Which of the following molecules A) CH 3 OCH 3 C) CH 3 CH 2 OH B) CH 3 COOH D) CH 3 CHO are likely to form hydrogen bonds? 1. C and D only

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purdy (sbp456) – Homework 1 – flowers – (53885) 2 2. B and C only correct 3. None forms hydrogen bonds. 4. A and C only 5. Another combination of compounds 6. A and D only 7. B and D only 8. A and B only 9. All are likely to form hydrogen bonds. Explanation: Only molecules with H attached to the electronegative atoms N, O, and F can hy- drogen bond. Of the molecules given, only CH 3 COOH and CH 3 CH 2 OH have hydrogen attached to oxygen, so these are the only ones that can undergo hydrogen bonding.
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