AP Chemistry Taylor Unit 9 Progress Check FRQ Scoring Guide.

For parts of the free-response question that require calculations, clearly show the method used and the steps involved in arriving at your answers. You must show your work to receive credit for your answer. Examples and equations may be included in your answers where appropriate. Answer the following questions related to . Substance at (a) Using the information in the table above, determine the value of at for the process represented by the equation . Please respond on separate paper, following directions from your teacher. (b) Considering your answer to part (a), indicate whether the process is thermodynamically favorable at . Justify your answer. Please respond on separate paper, following directions from your teacher. (c) Considering your answer to part (b), explain why has a measurable equilibrium vapor pressure at . Please respond on separate paper, following directions from your teacher. Water vapor can be produced in two different processes, as represented below. Process 1 Process 2 (d) In terms of concepts of entropy and the particle-level structure of the different phases of water, explain why the change in entropy, , is greater for process 1 than for process 2. AP Chemistry Scoring Guide Unit 9 Progress Check: FRQ Please respond on separate paper, following directions from your teacher. Part (a) Select a point value to view scoring criteria, solutions, and/or examples and to score the response. 0 1 The response includes both the following criteria: Part (b) Select a point value to view scoring criteria, solutions, and/or examples and to score the response. The answer to part (b) must be consistent with part (a). If a student makes an error in a previous part of the question, the student can still earn credit in a later part if the incorrect answer is used correctly. 0 1 The response indicates that the process is not thermodynamically favorable at because is positive.(OR, if part (a) indicates a negative value of ,the response indicates that the process is thermodynamically favorable because is negative.) Part (c) Select a point value to view scoring criteria, solutions, and/or examples and to score the response. AP Chemistry Scoring Guide Unit 9 Progress Check: FRQ 0 1 The response indicates that even though the process is not thermodynamically favorable, it does not follow that the process does not occur at all. At equilibrium, the reactant (liquid water) is favored over the product (water vapor). This does not mean that some of the liquid water cannot evaporate to become water vapor. Part (d) Select a point value to view scoring criteria, solutions, and/or examples and to score the response. 0 1 The response indicates that the change in entropy between ice, , and water vapor, , is greater because the entropy of water in the solid phase, with molecules bound in fixed positions within the solid, is less than the entropy of water in the liquid phase, with molecules able to move more freely and form a greater number of spatial configurations. Water in the gas phase, with molecules much more dispersed and even more free to move, has the highest entropy of the three phases. Therefore, process 1 (sublimation) involves a greater change in entropy than process 2 (evaporation from a liquid) does. 2. For parts of the free-response question that require calculations, clearly show the method used and the steps involved in arriving at your answers. You must show your work to receive credit for your answer. Examples and equations may be included in your answers where appropriate. Reaction 1: A chemist wants to produce from a sample of pure according to reaction 1, represented by the equation above. (a) Using the data in the following table, calculate the value of the standard entropy change, , for