Exam 1-solutions - Version 002 Exam 1 fakhreddine (51650)...

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Version 002 – Exam 1 – fakhreddine – (51650) 1 This print-out should have 27 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices before answering. 001 10.0 points Decreasing order means from MOST soluble to LEAST soluble in heptane! Rank the following liquids in decreasing order of solubility in heptane (C 7 H 16 ): NH 3 , CH 3 OH, CH 3 CH 2 ±, CCl 4 . 1. CH 3 CH 2 ± > CCl 4 > CH 3 OH > NH 3 2. CH 3 CH 2 ± > CH 3 OH > CCl 4 > NH 3 3. NH 3 > CH 3 OH > CH 3 CH 2 ± > CCl 4 4. CCl 4 > CH 3 CH 2 ± > NH 3 > CH 3 OH 5. CCl 4 > CH 3 CH 2 ± > CH 3 OH > NH 3 correct Explanation: ”Like dissolves like.” Heptane is hydrocar- bon, and thus completely non-polar. Car- bon tetrachloride is most soluble since even though the C-Cl bond are polar, there is no net dipole in the molecule, followed by ²uo- roethane, which is polar. Methanol is small and very polar (exhibiting hydrogen bond- ing), and ammonia is the most polar of the liquids, and thus least soluble. 002 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 3 H 8 , C 6 H 14 , C 5 H 11 OH , C 5 H 11 Cl , CaBr 2 2. C 6 H 14 , C 3 H 8 , C 5 H 11 OH , C 5 H 11 Cl , CaBr 2 3. C 3 H 8 , C 5 H 11 OH , C 6 H 14 , C 5 H 11 Cl , CaBr 2 4. C 3 H 8 , C 6 H 14 , C 5 H 11 Cl , C 5 H 11 OH , CaBr 2 correct 5. CaBr 2 , C 5 H 11 OH , C 5 H 11 Cl , C 6 H 14 , C 3 H 8 6. CaBr 2 , C 5 H 11 Cl , C 6 H 14 , C 5 H 11 OH , C 3 H 8 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. 003 10.0 points Of the following compounds, 3 , 4 , Ge± 4 , Al± 3 , Cs± which would you expect to have the lowest melting point? 1. 3 2. Al± 3 3. Ge± 4 4. Cs± 5. 4 correct Explanation: The greater the intermolecular forces bonds, the more energy required to break
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Version 002 – Exam 1 – fakhreddine – (51650) 2 those bonds and thus the greater the melting points or boiling points. The intermolecular forces, from strongest to weakest, are ion-ion, hydrogen bonding, dipole-dipole, and disper- sion forces. CsF ion-ion
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Exam 1-solutions - Version 002 Exam 1 fakhreddine (51650)...

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