1 Base your answers to questions 1 through 4 on the information below and on your knowledge of A student prepares two 141-gram mixtures, A and B. Each mixture consists of, sand, and at 15 C. Both mixtures are thoroughly stirred and allowed to stand. The mass of each component used to make the mixtures is listed in the data table below. 1. Describe one property of sand that would enable the student to separate the sand from the other components in mixture B. 2. Determine the temperature at which all of the in mixture A dissolves to form a saturated solution. 3. Which type of mixture is mixture B? 4. State evidence from the table indicating that the proportion of the components in a mixture can vary.
2 Base your answers to questions 5 through 7 on the information below and on your knowledge of A laboratory technician is given the table below and a sample of one of the three substances listed in the table. The technician makes an aqueous solution with a portion of the sample. When a conductivity tester is lowered into the solution, the lightbulb on the tester glows brightly. Another portion of the sample is placed in a heat-resistant container that is placed in an oven at 450 C. The sample melts. 5. Explain, in terms of ions, why an aqueous solution of potassium chromate conducts an electric current. 6. State evidence that makes it necessary to use more than one property to identify the substance given to the technician. 7. Identify the substance given to the technician. Base your answers to questions 8 through 11 on the information below and on your knowledge of Hydrazine,, is a compound that is very soluble in water and has a boiling point of 113 C at standard pressure. Unlike water, hydrazine is very reactive and is sometimes used as a fuel for small rockets. One hydrazine reaction producing gaseous products is represented by the balanced equation below. 8. Explain, in terms of intermolecular forces, why the boiling point of hydrazine at standard pressure is higher than the boiling point of water as standard pressure. 9. Explain, in terms of molecular polarity, why is very soluble in water. 10. Based on Table S, determine the electronegativity difference for the N-H bond in hydrazine. 11. Compare the entropy of the products to the entropy of the reactant for this reaction. 12. Based on Table H, state the vapor pressure of ethanol at 75 C.
3 Base your answers to questions 13 through 15 on the information below and on your knowledge of Seawater contains dissolved salts in the form of ions. Some of the ions found in seawater are An investigation was conducted to determine the concentration of dissolved salts in seawater at one location. A 300.-gram sample of the seawater was placed in an open container. After a week, all the water had evaporated and 10. grams of solid salts remained in the container. 13. Explain why the evaporation that occurred during the investigation is an endothermic process. 14. At standard pressure, compare the freezing point of seawater to the freezing point of distilled water. 15. Determine the concentration, expressed as percent by mass, of the dissolved salts in the original sample of seawater. Base your answers to questions 16 through 18 on on the information below. 18. Determine the temperature range over which the entire NaCl sample is a liquid. A gram sample of NaCl(s) has an initial temperature of 0 C. A chemist measures the temperature of the sample as it is heated. Heat is not added at a constant rate. The heating curve for the sample is shown below. 16. Identify one line segment on the curve where the NaCl sample is in a single phase and capable of conducting electricity. 17. Identify one line segment on the curve where the average kinetic energy of the particles of the NaCl sample is changing.
4 Base your answers to questions 19 and 20 on the information and table below. A student conducts an experiment to determine how the temperature of water affects the rate at which an antacid tablet dissolves in the water. The student has three antacid tablets of the same size and composition. The student drops one tablet into each of three beakers containing 200. milliliters of water at different temperatures and measures the time it takes for each tablet to completely dissolve. The results are shown in the table below. 19. Explain, in terms of collision theory, how water temperature influences the rate of dissolving. 20. Describe the effect of water temperature on the rate of dissolving.
5 21. Base your answer to the following question on the graph below, which represents the cooling of a substance starting at a temperature above its boiling point. What is the melting point of this substance? 22. What is the total amount of heat energy, in joules, absorbed by 25.0 grams of water when the temperature of the water increases from 24.0 C to 36.0 C? Base your answers to questions 23 through 25 on the information below. Element X is a solid metal that reacts with chlorine to form a water-soluble binary compound. 23. The binary compound consists of element X and chlorine in a 1:2 molar ratio. What is the oxidation number of element X in this compound? 24. Explain, in terms of particles, why an aqueous solution of the binary compound conducts an electric current. 25. State one physical property of element X that makes it a good material for making pots and pans. 26. A sample of oxygen gas in one container has a volume of 20.0 milliliters at 297 K and kpa. The entire sample is transferred to another container where the temperature is 283 K and the pressure is 94.6 kpa. Show a correct numerical setup for calculating the new volume of this sample of oxygen gas.