Chem 112 exam 2 questions and answers guaranteed pass

H2O has a stronger molecular bond due to the presence of hydrogen bonding with oxygen. - correct answers Which has the stronger intermolecular forces, N2 or H2)? Explain. - correct answers Which gas would behave more ideally at the same conditions of pressure and temperature? CO or N₂? Why? Wax and water can be both a solid and a liquid respectively because the density of the solid wax is higher than that of water. - correct answers Wax consists of long chain non-polar hydrocarbons that exhibit London dispersion forces. Water exhibits hydrogen bonding. Individual hydrogen bonding interactions are stronger than individual London dispersion interactions. So, how can wax be a solid and water a liquid at normal conditions? False. A molecule that contains polar bonds may or may not be polar, depending on its shape. Molecules that do not contain polar bonds are not polar unless the central atom has one or more nonbonded pairs of electrons. - correct answers True or false? All molecules with polar bonds are polar. False. H2O will have a stronger bond because of hydrogen bonding with oxygen. CH4 does not form a hydrogen bond at all. Hydrogen bonding is the bonding is a special dipole-dipole interaction between a hydrogen atom in a polar bond with either N,O, or F atom. - correct answers True or false? Methane(CH4) is more likely to form stronger hydrogen bonding than water because each methane molecule has twice as many hydrogen atoms. Provide a concise explanation of hydrogen bonding to go with your answer. Nitrogen exists as a gas at certain conditions and as a liquid at lower temperatures. Lowering the temperature would cause the nitrogen to undergo a phase change from gas to liquid. - correct answers Why should it make sense that N₂ exists as a gas? Given your answer to this, how is it possible to make liquid nitrogen? Explain why lowering the temperature works. The vapor pressure of water at 100°C is 760 mmHg. This is known because vapor pressure increases with temperature. - correct answers What is the vapor pressure of water at 100°C? How do you know? Because the boiling point of water can vary due to changes in atmospheric pressure. - correct answers Claiming that the boiling point of water is 100°C is not necessarily incorrect, but it is incomplete. Explain why. a. As intermolecular forces increase, the boiling point increases. Because more energy is needed to break stronger bonds. b. Liquids with stronger intermolecular forces have higher viscosities than those with weak intermolecular forces. c. As intermolecular forces increase, the surface tension of liquids increases. d. e. f. - correct answers As intermolecular forces increase, what happens to each of the following? Why? a. boiling point b. viscosity c. surface tension d. Enthalpy of fusion e.Vapor Pressure f. heat of vaporization The ∆Hvap would be higher because the molecules in a liquid are packed closely together, so energy is needed to bring about the rearrangement from solid to liquid. When a liquid evaporates, its molecules are completely separated from one another and more energy is required to overcome the attractive forces. - correct answers Which would you predict to be larger for a given substance:∆Hvap or ∆Hfus. Explain why. - correct answers A metal crystallizes in a body-centered cubic structure. Determine the relationship between the radius of the metal atom and the length of an edge of the unit cell. Ionic solids have high melting pints, and indication of strong cohesive forces holding ions together. Ionic solids do not conduct electricity because the ions are fixed in position. - correct answers Explain the difference among ionic, atomic, and molecular solids. Provide an example of each Diamonds are not considered molecular solids because diamonds although made of carbon, each carbon is tetrahedrally bonded to four other atoms. - correct answers White phosphorous and sulfur are each called molecular solids even though each is made of only phosphorous and sulfur, respectively. How can they be considered molecular solids? If this is true, why isn't diamond (which is made up only of carbon) a molecular solid? - correct answers Why is it incorrect to use the term molecule of NaCl but correct to use the term molecule of H₂)? Is the term molecule of diamond correct? Explain. Dispersion→Dipole-induced→Ion-Induced→Dipole-Dipole→H Bond→Ion-Dipole - correct answers Sort the intermolecular forces shown below by increasing strength of interaction. DISPERSION: H₂ Ar CH₂Cl₂ H₂S HCN HF NH₃ CH₃OH PF₅ DIPOLE-DIPOLE: CH₂Cl₂ H₂S HCN BrCl₅ NH₃ CH₃OH HF H BOND: NH₃ HF CH₃OH - correct answers Classify the species given below by the intermolecular forces present in a pure sample of each. HF CH₃COOH NH₃ - correct answers Which of the following species are capable of hydrogen bonding among themselves? A dipole-dipole interaction is the attractive intermolecular forces between the permanent dipoles of two polar molecules. An attractive intermolecular force that occurs when a hydrogen atom bonded to O, N, or F is electrostatically attracted to an O, N, or F atom in another molecule is called hydrogen bonding. The London dispersion force is the very weak intermolecular interactions due to the momentary changes in electron density in a molecule. The normal boiling point is the temperature at which the vapor pressure above a liquid equals 760 mmHg. The vapor pressure is the pressure above a liquid exerted by gas particles in equilibrium with the liquid phase. The surface tension is a measure of the resistance of a liquid to spread out. - correct answers Select the keyword or phrase that will best complete each sentence. ethanol - correct answers Predict which of the following liquids has greater surface tension: ethanol (C2H5OH) or dimethyl ether (CH3OCH3). - correct answers The vapor pressure of ethanol is 100 mmHg at 34.9°C. What is its vapor pressure at 55.0°C? (ΔHvap for ethanol is 39.3 kJ/mol.) LiF, melting point 845°C: ionic dispersion BeF2, melting point 800°C: dispersion BF3, melting point −126.7°C: dispersion CF4, melting point −184°C: dispersion NF3, melting point −203.3°C: dipole-dipole dispersion OF2, melting point −223.8°C: dipole-dipole dispersion F2, melting point −219.6°C: dipole-dipole dispersion - correct answers Classify the type(s) of intermolecular forces present in each of the following fluorides of the second-period elements. very low vapor pressure - correct answers Which of the following properties indicates very strong intermolecular forces in a liquid? Atomic Solids Ar, Xe Molecular Solids N₂, CH₂F₂, CO₂, PCl₅ Ionic Solids MgCl₂, CaO, KBr Metallic Solids Au, Cd, Co Network Covalent Solids SiO₂, C - correct answers Classify each of the species given below by the type of crystalline solid it forms. ionic - correct answers A solid is hard, brittle, and electrically nonconducting. Its melt (the liquid form of the substance) and an aqueous solution containing the substance conduct electricity. Classify the solid. a. The higher the temperature‚ the faster the evaporation. b. The greater the surface are‚ the greater the rate of evaporation. c.The weaker the intermolecular forces‚ the faster the evaporation. - correct answers How is the rate of evaporation of a liquid affected by (a) temperature, (b) the surface area of liquid exposed to air, (c) intermolecular forces? At −10°C, which of these liquids would you expect to have the highest vapor pressure? butane At −10°C, which of these liquids would you expect to have the lowest vapor pressure? toluene - correct answers The following compounds are liquid at −10°C: butane (boiling point −0.5°C); ethanol (boiling point 78.3°C); toluene (boiling point 110.6°C). Boil liquid ammonia: dipole-dipole interactions hydrogen bonding dispersion forces (b) Melt solid phosphorus (P4): dispersion forces (c) Dissolve CsI in liquid HF: ionic bonding dispersion forces hydrogen bonding dipole-dipole interactions (d) Melt potassium metal: dispersion forces - correct answers Name the kinds of attractive forces that must be overcome in order to perform the following tasks. Select all that apply. 10.50 cm³ - correct answers When silver crystallizes, it forms face-centered cubic cells. The unit cell edge length is 408.7 pm. Calculate the density of silver in g/cm3. when its temperature is lowered. The vapor pressure decreases. (b) when the volume of the container is doubled. The vapor pressure doesn't change. (c) when more water is added to the beaker. The vapor pressure doesn't change. - correct answers A beaker of water is placed in a closed container. Predict the effect on the vapor pressure of the water... 8 - correct answers When silver crystallizes, it forms face-centered cubic cells. The unit cell edge length is 408.7 pm. Calculate the density of silver in g/cm3. 3.61x 10² - correct answers Copper crystallizes in a face-centered cubic lattice (the Cu atoms are at the lattice points and at the face centers). If the density of the metal is 8.96 g/cm3, what is the unit cell edge length in pm?