University:
Arizona State University
Course:
CHM 101 | Introductory Chemistry
Academic year:

2023
Views:

138

Pages:

2
Author:

Charlee Buchanan

Graded Assignment Unit Test, Part 2 (5 points) 1. You watch water falling from the top of a waterfall to the bottom. How would you characterize this physical phenomenon in terms of spontaneity? What if you wanted to move the water from the bottom of the falls to the top—how would you characterize that reaction? Score Click here to enter text. Answe: Water falling from the top of the fall to the bottom is a spontaneous process. Raising water from the bottom to the top of the waterfall is a non-spontaneous process. (8 points) 2. Consider the following reaction occurring in a closed chemical system. Assume that this reaction is at equilibrium and that in general the reaction to the right is favored. CH3CH2OH + 3O2 2CO2 + 3H2O ∆H = –1,235 kJ/mol What type of chemical reaction is this? If more CH3CH2OH is added to the system, how will the reactions shift to reach equilibrium again? If water is extracted from the system, how will the reactions shift to reach equilibrium again? If heat is removed from the system, how will the reactions shift to reach equilibrium again? What is the name of the principle that helps you predict each of these shifts in equilibrium? Answer: `This is an exothermic reaction. `The equilibrium will shift to the right to consume the reactant and counter this change. The equilibrium will shift to the right to produce more water and counter this change. The equilibrium will shift to the right to produce more heat and counter this change. `The name of the principle that helps me predict each of these shifts is the Le Chatelier's principle. Score Click here to enter text. (8 points) 3. This graph shows the energy involved in a reaction involving two molecules. Describe what is happening or what the state of the reaction is at A, B, C, and D. Then tell if this is an exothermic or an endothermic reaction. Score Click here to enter text. Answer: A: The bond is breaking B: Transition state C: New formed bond D: Energy releasing This graph represents an Exothermic reaction. (5 points) 4. Chalcocite is an ore from which copper can be extracted for commercial use. The formula for this important ore is Cu2S. In the laboratory it is formed by the following reaction: Score Click here to enter text. 2Cu + S → Cu2S The reaction takes place in laboratory conditions that allow the reactant atoms to move freely about in the reaction vessel. Explain this reaction in terms of collision theory. Answer: 2 moles of Cu atoms are mixed with 1 mole of S atoms. Then either heat or stir allowing for the atoms to collide. Then when 2 Cu atoms collide with 1 S atom, Cu2S is formed. Your Score Click here to enter text. of 26