Homework 3 PDF

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Question 1 In a single molecule of water, the oxygen atom is bonded to two hydrogen atoms by... Non-polar covalent bonds xPolar covalent bonds Hydrogen bonds Ionic bonds None of the above In a single molecule of water, the oxygen atom is bonded to the two hydrogen atoms by polar covalent bonds. CONSEQUENTLY, water molecules are polar and can hydrogen bond to each other. Question 2 In the liquid phase of water, multiple water molecules are held together by… Nonpolar covalent bonds Polar covalent bonds Ionic bonds xHydrogen bonds None of the above In the liquid phase of water, individual water molecules are held together by the attraction between the partial positive charges on hydrogen atoms and the partial negative charges on oxygen atoms. The partial positive charge on hydrogen, and the partial negative charge on oxygen both result from the nonpolar covalent bonds they form with each other. When the partial positive charge on a hydrogen atom of a polar covalent bond in one molecule is attracted to the partial negative charge of a polar covalent bond in another atom, the attraction is called a hydrogen bond. Question 3 True or false? In the solid phase of water, each water molecule is hydrogen bonded to four other water molecules; and the hydrogen bonds are of maximum length.

xTrue False Both statements are true. THEREFORE, the correct answer is true. Because the water molecules in ice are spaced further apart, a given volume of ice is less dense than the same volume of liquid water. Question 4 True or false? In liquid water, a single water molecule is hydrogen bonded to an average of 3.4 other water molecules. Hydrogen bonding among water molecules causes them to cling together making bodies of water cohesive. True xFalse

Both statements are true. Thus, the entire statement is true. All the emergent properties of bodies of water depend to one degree or another on hydrogen bonding among water molecules. Question 5 Which statement (or statements) accurately describes the concept of heat? For a defined body of matter, heat is the average kinetic energy of its atoms or molecules x For a defined body of matter, heat is the total kinetic energy of all its atoms or molecules The heat contained in a defined body of matter deponds on the body's volume a and b b and c Heat is defined as the total kinetic energy of all the atoms/molecules within a body of matter. THEREFORE, the heat of a body of matter depends on its overall size/volume, and choice (b) and (c) are correct. Question 6 True or false? A body of water has a high specific heat because energy that is absorbed by the body must break ionic bonds between H+ and OH- ions before it can increase their kinetic energy. xTrue False While the statement is partially true, energy that is absorbed by a body of water must break hydrogen bonds between water molecules not ionic bonds. Water is not an ionic compound. Question 7 Which statement describes a solution? A solution is a disolving agent that is always a liquid A solution is a substance (solid, liquid, or gas) that is disolved A solution is a gas that consists of homogenous mixture of two or more substances A solution is a solid that consists of homogenous mixture of two or more substances x None of the above The correct choice is (e) none of the above. Choices (c) and (d) come close to the definition. However, a solution is always a liquid. It is never a gas or solid. Question 8 Which statements (or statements) describes a substance that is hydrophilic? A hydrophilic substance does not dissolve in water xA hydrophilic substance does dissolve in water Hydrophilic substances typically have large numbers of non-polar covalent bonds All of the above None of the above By definition, hydrophilic substances dissolve well in water. They typically have large numbers of polar covalent bonds. THUS, the correct choice is (b). Question 9

Which statement (or statements) describes a hydrophobic substance? xA hydrophobic substance typically has large number of non-polar covalent bonds A hydrophobic substance typically has large number of polar covalent bonds A hydrophobic substance typically has large number of charged regions All of the above None of the above Hydrophobic substances do not dissolve well in water. CONSEQUENTLY, they must have large numbers of non-polar covalent bonds. Question 10 Suppose that I have one liter of water in which the ionization of water has reached equilibrium. What is the concentration of H+ ions? 1/10,000,000 moles/liter x10 raised to the -7th power moles/liter 10 raised to the 7th power moles/liter a and b b and c The correct choice is 10 raised to the -7 moles/liter. However, this is equal to 1/10,000,000 moles/liter...