Free Response Review Packet

Transcription

1 1. Base your answer to the following question on the information below and on your knowledge of chemistry. Illuminated EXIT signs are used in public buildings such as schools. If the word EXIT is green, the sign may contain the radioisotope tritium, hydrogen-3. The tritium is a gas sealed in glass tubes. The emissions from the decay of the tritium gas cause a coating on the inside of the tubes to glow. State, in terms of neutrons, how an atom of tritium differs from an atom of hydrogen-1. Base your answers to questions 2 and 3 on A student compares some models of the atom. These models are listed in the table below in order of development from top to bottom. 2. State one way in which the Bohr model agrees with the Thomson model. 3. Using the conclusion from the Rutherford model, identify the charged subatomic particle that is located in the nucleus.

2 4. Base your answer to the following question on Chemical concepts are applied in candy making. A recipe for making lollipops is shown below. Ingredients: 414 grams of sugar 177 grams of water 158 milliliters of light corn syrup Hard-Candy Lollipops Recipe Step 1: In a saucepan, mix the sugar and water. Heat this mixture, while stirring, until all of the sugar dissolves. Step 2: Add the corn syrup and heat the mixture until it boils. Step 3: Continue boiling the mixture until the temperature reaches 143 C at standards pressure. Step 4: Remove the pan from the heat and allow it to stand until the bubbling stops. Pour the mixture into lollipop molds that have been coated with cooking oil spray. Explain, in terms of the concentration of sugar molecules, why the boiling point of the mixture in step 3 increases as water evaporates from the mixture. 5. Base your answer to the following question on Two very stable compounds, Freon-12 and Freon-14, are used as liquid refrigerants. A Freon-12 molecule consists of one carbon atom, two chlorine atoms, and two fluorine atoms. A Freon-14 molecule consists of one carbon atom and four fluorine atoms. To which class of organic compounds do Freon-12 and Freon-14 belong?

3 6. Base your answer to the following question on the information below. The bright-line spectra for three elements and a mixture of elements are shown below. Explain, in terms of both electrons and energy, how the bright-line spectrum of an element is produced. 7. Copper has two naturally occurring isotopes. Information about the two isotopes is shown in the table below. In the space in your answer booklet, show a numerical setup for calculating the atomic mass of copper. 8. In the box below, draw a Lewis electron-dot diagram for an atom of boron.

4 9. Determine the mass number of the magnesium atom represented by the electron-shell diagram. 10. Write one electron configuration for an atom of silicon in an excited state. 11. Base your answer to the following question on There are six elements in Group 14 on the Periodic Table. One of these elements has the symbol Uuq, which is a temporary, systematic symbol. This element is now known as flerovium. Explain, in terms of electron shells, why each successive element in Group 14 has a larger atomic radius, as the elements are considered in order of increasing atomic number. 12. Explain, in terms of atomic structure, why Group 18 elements on the Periodic Table rarely form compounds. 13. Explain, in terms of electrons, why the radius of a potassium atom is larger than the radius of a potassium ion in the ground state.

5 14. Base your answer to the following question on the information below and on your knowledge of chemistry. Silver-plated utensils were popular before stainless steel became widely used to make eating utensils. Silver tarnishes when it comes in contact with hydrogen sulfide,, which is found in the air and in some foods. However, stainless steel does not tarnish when it comes in contact with hydrogen sulfide. Draw a Lewis electron-dot diagram for the compound that tarnishes silver. 15. Base your answer to the following question on The diagram below represents three elements in Group 13 and three elements in Period 3 and their relative positions on the Periodic Table. Some elements in the solid phase exist in different forms that vary in their physical properties. For example, at room temperature, red phosphorus has a density of 2.16 g/cm 3 and white phosphorus has a density of g/cm 3. Consider the Period 3 elements in the diagram in order of increasing atomic number. State the trend in electronegativity for these elements.

6 16. Base your answer to the following question on Before atomic numbers were known, Mendeleev developed a classification system for the 63 elements known in 1872, using oxide formulas and atomic masses. He used an R in the oxide formulas to represent any element in each group. The atomic mass was listed in parentheses after the symbol of each element. A modified version of Mendeleev's classification system is shown in the table below. Based on Mendeleev's oxide formula, what is the number of electrons lost by each atom of the elements in Group III? 17. Base your answer to the following question on the information below. The atomic radius and the ionic radius for some Group 1 and some Group 17 elements are given in the tables below. Explain, in terms of electron shells, why the radius of a K + ion is greater than the radius of an Na + ion.

7 Base your answers to questions 18 through 21 on the information below. Two sources of copper are cuprite, which has the IUPAC name copper(i) oxide, and malachite, which has the formula Cu2CO3(OH)2. Copper is used in home wiring and electric motors because it has good electrical conductivity. Other uses of copper not related to its electrical conductivity include coins, plumbing, roofing, and cooking pans.aluminum is also used for cooking pans. At room temperature, the electrical conductivity of a copper wire is 1.6 times greater than an aluminum wire with the same length and cross-sectional area. At room temperature, the heat conductivity of copper is 1.8 times greater than the heat conductivity of aluminum. At STP, the density of copper is 3.3 times greater than the density of aluminum. 18. Identify one physical property of aluminum that could make it a better choice than copper for a cooking pan. 19. Identify one physical property of copper that makes it a good choice for uses that are not related to electrical conductivity. 20. Determine the oxidation number of oxygen in the carbonate ion found in malachite. 21. Write the chemical formula of cuprite. 22. Explain, in terms of electron configuration, why selenium and sulfur have similar chemical properties.

8 Base your answers to questions 23 through 25 on The formulas and the boiling points at standard pressure for ethane, methane, methanol, and water are shown in the table below. 23. Explain, in terms of molecular polarity, why the solubility of methanol in water is greater than the solubility of methane in water. 24. State the change in potential energy that takes place in a sample of methane as it boils at C. 25. Identify the compound that has the strongest intermolecular forces.

9 26. Base your answer to the following question on A 1.00-mole sample of glucose, by the balanced equation below., completely reacts with oxygen, as represented Using the axes above, complete the potential energy curve for the reaction of glucose with oxygen. 27. Base your answer to the following question on the information below and on your knowledge of chemistry. Rubbing alcohol is a product available at most pharmacies and supermarkets. One rubbing alcohol solution contains 2-propanol and water. The boiling point of 2-propanol is 82.3 C at standard pressure. Explain in terms of electronegativity differences, why a C O bond is more polar than a C H bond. 28. Base your answer to the following question on the information below. Ammonium chloride is dissolved in water to form a 0.10 M NH 4Cl(aq) solution. This dissolving process is represented by the equation below. Determine the minimum mass of NH4Cl(s) required to produce a saturated solution in 100. grams of water at 40. C.

10 Base your answers to questions 29 and 30 on the information below. In 1864, the Solvay process was developed to make soda ash. One step in the process is represented by the balanced equation below. NaCl + NH3 + CO2 + H2O NaHCO3 + NH4Cl 29. In the space draw a Lewis electron-dot diagram for the reactant containing nitrogen in the equation. 30. Write the chemical formula for one compound in the equation that contains both ionic bonds and covalent bonds. 31. Base your answer to the following question on the information below. Carbon has three naturally occurring isotopes, C-12, C-13, and C-14. Diamond and graphite are familiar forms of solid carbon. Diamond is one of the hardest substances known, while graphite is a very soft substance. Diamond has a rigid network of bonded atoms. Graphite has atoms bonded in thin layers that are held together by weak forces. Recent experiments have produced new forms of solid carbon called fullerenes. One fullerene, C60, is a spherical, cagelike molecule of carbon. State, in terms of the arrangement of atoms, the difference in hardness between diamond and graphite.

11 32. Base your answer to the following question on the information below. Explain why Lewis electron-dot diagrams are generally more suitable than electron-shell diagrams for illustrating chemical bonding. Base your answers to questions 33 through 36 on the table below. 33. Explain, in terms of molecular polarity, why hydrogen chloride is more soluble than hydrogen in water under the same conditions of temperature and pressure.

12 34. Explain, in terms of intermolecular forces, why hydrogen has a lower boiling point than hydrogen bromide. 35. The density of hydrogen at STP is gram per liter. Express this density to two significant figures. 36. The volume of 1.00 mole of hydrogen bromide at STP is 22.4 liters. The gram-formula mass of hydrogen bromide is 80.9 grams per mole. What is the density of hydrogen bromide at STP? Base your answers to questions 37 and 38 on The diagram below represents a cylinder with a movable piston. The cylinder contains 1.0 liter of oxygen gas at STP. The movable piston in the cylinder is pushed downward at constant temperature until the volume of 0 2(g) is 0.50 liter. 37. State the effect on the frequency of gas molecule collisions when the movable piston is pushed farther downward into the cylinder. 38. Determine the new pressure of O2(g) in the cylinder, in atmospheres. Base your answers to questions 39 and 40 on A few pieces of dry ice,, at are placed in a flask that contains air at. The flask is sealed by placing an uninflated balloon over the mouth of the flask. As the balloon inflates, the dry ice disappears and no liquid is observed in the flask. 39. Write the name of the process that occurs as the dry ice undergoes a phase change in the flask. 40. State the direction of heat flow that occurs between the dry ice and the air in the flask.

13 41. Base your answer to the following question on the information below and on your knowledge of chemistry. Paintball is a popular recreational activity that uses a metal tank of compressed carbon dioxide or nitrogen to launch small capsules of paint. A typical tank has a volume of 508 cubic centimeters. A 340.-gram sample of carbon dioxide is added to the tank before it is used for paintball. At 20. C, this tank contains both CO2(g) and CO2( ). After a paintball game, the tank contains only CO2(g). In the box above, use the key to draw a particle diagram to represent the two phases of CO 2 in a newly filled tank. Your response must include at least six molecules of CO2 in each phase. Base your answers to questions 42 and 43 on the information below. A student investigated heat transfer using a bottle of water. The student placed the bottle in a room at 20.5 C. The student measured the temperature of the water in the bottle at 7 a.m. and again at 3 p.m. The data from the investigation are shown in the table below. 42. Show a numerical setup for calculating the change in the thermal energy of the water in the bottle from 7 a.m. to 3 p.m. 43. State the direction of heat transfer between the surroundings and the water in the bottle from 7 a.m. to 3 p.m.

14 Base your answers to questions 44 and 45 on the information below. Starting as a gas at 206 C, a sample of a substance is allowed to cool for 16 minutes. This process is represented by the cooling curve below. 44. Using the key below, draw two particle diagrams to represent the two phases of the sample at minute 4. Your response must include at least six particles for each diagram. 45. At what time do the particles of this sample have the lowest average kinetic energy?

15 46. Base your answer to the following question on Heat is added to a sample of liquid water, starting at 80.ºC, until the entire sample is a gas at 120.ºC. This process, occurring at standard pressure, is represented by the balanced equation below. H2O( ) + heat H2O(g) On the diagram below, complete the heating curve for this physical change. 47. A liquid boils when the vapor pressure of the liquid equals the atmospheric pressure on the surface of the liquid. Using Reference Table H, determine the boiling point of water when the atmospheric pressure is 90. kpa. 48. Base your answer to the following question on Many breads are made by adding yeast to dough, causing the dough to rise. Yeast is a type of microorganism that produces the catalyst zymase, which converts glucose,, to ethanol and carbon dioxide gas. The balanced equation for this reaction is shown below. Describe how the catalyst, zymase, speeds up this reaction. 49. Base your answer to the following question on the information below and on your knowledge of chemistry. The compounds and are soluble in water. Compare the entropy of 30. grams of solid at 20. C with the entropy of 30. grams of dissolved in 100. grams of water at 20. C.

16 Base your answers to questions 50 and 51 on the information below. The chemical reaction between methane and oxygen is represented by the potential energy diagram and balanced equation below. 50. Explain, in terms of collision theory, why a lower concentration of oxygen gas decreases the rate of this reaction. 51. Which potential energy interval in the diagram represents the activation energy of the forward reaction? 52. Base your answer to the following question on Propane is a fuel that is sold in rigid, pressurized cylinders. Most of the propane in a cylinder is liquid, with gas in the space above the liquid level. When propane is released from the cylinder, the propane leaves the cylinder as a gas. Propane gas is C3H8(g) + 5O2(g) 2CO2(g) + 4H2O( ) kJ A small amount of methanethiol, which has a distinct odor, is added to the propane to help consumers detect a propane leak. In methanethiol, the odor is caused by the thiol functional group ( SH). Methanethiol, CH3SH, has a structure that is very similar to the structure of methanol. Draw a particle diagram to represent propane in a pressurized cylinder. Your response must include at least six molecules of propane in the gas phase and at least six molecules of propane in the liquid phase.

17 53. Explain, in terms of collision theory, why the rate of a chemical reaction increases with an increase in temperature. 54. A potential energy diagram for a chemical reaction is shown below. On this diagram, draw a curve to show how the potential energy diagram will change when a catalyst is added to the reaction. Base your answers to questions 55 and 56 on the information below. A method used by ancient Egyptians to obtain copper metal from copper(i) sulfide ore was heating the ore in the presence of air. Later, copper was mixed with tin to produce a useful alloy called bronze. 55. Convert the melting point of the metal obtained from copper(i) sulfide ore to degrees Celsius. 56. Calculate the density of a -gram sample of bronze that has a volume of cubic centimeters. Your response must include a correct numerical setup and the calculated result. 57. Based on data collected during a laboratory investigation, a student determined an experimental value of 322 joules per gram for the heat of fusion of H2O. Calculate the student's percent error. Your response must include a correct numerical setup and the calculated result.

18 Base your answers to questions 58 and 59 on the information below. A student performed an experiment to determine the total amount of energy stored in a peanut. The accepted value for the energy content of a peanut is 30.2 kilojoules per gram. The student measured grams of water into a metal can and placed the can on a ring stand, as shown in the diagram below. The peanut was attached to a wire suspended under the can. The initial temperature of the water was recorded as 22.0 C. The peanut was ignited and allowed to burn. When the peanut finished burning, the final water temperature was recorded as 57.0 C. The student's experimental value for the energy content of this peanut was 25.9 kilojoules per gram. 58. Determine the student s percent error for the energy content of this peanut. 59. Calculate the total amount of heat absorbed by the water. Your response must include both a correct numerical setup and the calculated result.

19 Answer Key Quarter II Review 1. A tritium atom has two neutrons and an H-1 atom has no neutrons. Only the tritium atom has neutrons. H-1 has no neutrons. 2. Atoms have electrons. Atoms have small, negatively charged particles. Both models show an internal structure. Atoms are neutral. 3. proton p p + 11p 1 1 H H + 4. The boiling point of the mixture increases as water evaporates because the concentration of dissolved molecules increases. An increase in the concentration of sugar particles increases the boiling point. 5. halide halocarbon 6. When electrons in an excited state return to a lower energy state, specific amounts of energy are emitted. These energies are associated with specific wavelengths of light that are characteristic of the bright-line spectrum of an element. Energy is emitted when excited electrons fall back to lower shells. 7. Acceptable responses include, but are not limited to: (62.93 u)(0.6917) + (64.93 u)(0.3083) or Examples: ; ; ; The atomic radius of these elements increases down the group because each successive element has one more electron shell. The number of shells per atom increases. 12. Group 18 elements rarely form compounds because their atoms have stable electron configurations. Their valence shells are completely filled. All the elements have maximum numbers of valence electrons. Atoms of Group 18 have a stable octet except He, which is stable with two electrons. 13. A potassium atom has four electron shells and a potassium ion has three electron shells. A potassium atom has one more electron shell than a potassium ion. A K + ion has one fewer electron than a K atom As atomic number increases, the electronegativity increases. Electronegativity increases. from lower to higher 16. three electrons three —A K + ion has three electron shells and an Na + ion has only two. —A sodium ion has fewer electron shells than a potassium ion. 18. An aluminum pan has less mass than a copper pan of the same size because aluminum is less dense. Aluminum is less dense than copper. A Cu pan would weigh more. 19. Copper is very malleable or a good conductor of heat or a high melting point Cu2O 22. Examples: An atom of each element has six electrons in its outer shell. same number of valence electrons 23. Methanol and water molecules are polar, but methane molecule are nonpolar. The compounds methanol and water have similar polarities. 24. As liquid methane boils, the potential energy of the sample increases. Potential energy increases. higher PE 25. H2O/water 26.

20 Answer Key Quarter II Review 27. There is a greater electronegativity difference in a CO bond than in a CH bond. The CO bond is more polar because the electronegativity difference for a CO bond is 0.8, and the electronegativity difference for a CH bond is 0.4. The CH bond has a smaller difference. The CO is.8 and the CH is g 1 g NaHCO3 or NH4Cl. 31. Diamond has atoms bonded strongly in a three-dimensional network. Graphite has atoms that are held weakly between layers. 32. Lewis electron-dot diagrams only show valence electrons, which are involved in bonding. 33. Examples: HCl's molecular polarity is more similar to water's polarity than H 2's polarity compared to water's HCl and water both polar, H2 nonpolar, like dissolves like HCl polarity is more similar to water's polarity 34. Examples: Hydrogen has weaker intermolecular forces than HBr. hydrogen weaker forces g/l or g/l g/l 37. When the piston is moved farther into the cylinder, the frequency of collision between the molecules increases. There will be more collisions per second. increased frequency atm/2.0 atm 39. sublimation subliming 40. Heat flows from the air in the flask to the dry ice. air to to dry ice from air q = (800. g)(4.18 J/g ºC)(20.5ºC 12.5ºC) (800)(4.18)(8) 43. Heat was transferred from the surroundings to the water in the bottle. The water absorbed energy from the surroundings minute 16 or at 16 minutes 46. a line is drawn horizontally to represent the phase change and extending the line with a positive slope to represent the gas phase, only C ± 1 C. 48. Zymase is a catalyst that provides an alternative pathway, which requires less energy. decreases the activation energy changes the reaction mechanism 49. The entropy of is less than the entropy of. The is more disordered. The solution is more random the solid. 50. Acceptable responses include, but are not limited to: A lower concentration of oxygen gas decreases the number of effective collisions between O2 molecules and CH4 molecules. 51. B As temperature increases, the rate of a chemical reaction increases because the reactant particles move faster and collide more often Answer: 1084ºC J/g 334 J/g J/g Examples: 3.6%; 4% % or 14%. 59.