Molecules Hw12

Molecules Hw12 - MasteringPhysics: Assignment Print View...

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[ Print View ] Physics 228 Spring 2008 Molecules and Condensed Matter Due at 11:59pm on Monday, April 21, 2008 View Grading Details What Holds Matter Together? Learning Goal: To be able to identify the various types of molecular and intermolecular bonds as well as their relative strengths. There are four major types of bonds that hold atoms and molecules together. The first two, ionic and covalent bonds, hold atoms together to form molecules. These are called molecular bonds. The other two, van der Waals and hydrogen bonds, hold molecules together to form solids or liquids. These are called intermolecular bonds. The hydrogen bond also plays a part in giving specific shapes to large organic molecules. Ionic bonds are formed when one atom gives up one or more electrons to another atom or atoms. The resulting oppositely charged atoms are held together by the electric force. In a covalent bond, two atoms share a pair of electrons with opposite spins. This creates a region of negative charge between the two now positively charged nuclei, thus holding them together through the electric force. In a van der Waals bond (sometimes called a London or dipole-dipole bond), electric dipole moments of molecules interact. Usually, the dipoles are induced by shifting charge distributions in nearby molecules. Molecules containing hydrogen often have a strong permanent dipole moment, because forming a covalent bond leaves the hydrogen nucleus as a relatively bare positive charge. The stronger bond formed by such dipole moments is called a hydrogen bond. The strength of a bond is measured by the bond energy, which is the amount of energy necessary to break the bond. In general, molecular bonds have bond energies of 1 to 5 . Hydrogen bonds have bond energies in the range 0.1 to 0.5 , and van der Waals bonds have bond energies less than or equal to 0.1 . Part A Consider the following bonds: 1. the bond between and in a molecule of 2. the bond between molecules 3. the bond between molecules Match each bond to its corresponding bond energy from the following list: A. 0.014 B. 4.2 C. 0.5 Type the three letters in the order that they match up to the numbers. For instance, if you think that the Page 1 of 14 MasteringPhysics: Assignment Print View 5/8/2008
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correct match is , then enter BAC as your answer. ANSWER: BCA Part B The bond energy for the van der Waals bond between two helium atoms is . Assuming that the average kinetic energy of a helium atom is , at what temperature is the average kinetic energy equal to the bond energy between two helium atoms? Use . Express your answer in kelvins to two significant figures. Since on average, a single helium atom has enough kinetic energy to break the van der Waals bond at 6.1
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This note was uploaded on 11/25/2010 for the course PHYSICS 228 taught by Professor Staff during the Spring '08 term at Rutgers.

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Molecules Hw12 - MasteringPhysics: Assignment Print View...

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