Preview of “Lab 8 PreLab - Eq. and LeChatelier's Principle”

Preview of “Lab 8 PreLab - Eq. and LeChatelier's Principle”

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Unformatted text preview: 11/6/12 Lab 8 PreLab -‐‑ Eq. and LeChatelier's Principle Steve Yarush CH102, section 021, Fall 2012 Instructor: Brandon Zoellner WebAssign Lab 8 PreLab -­ Eq. and LeChatelier's Principle (Prelab) Current Score : 25 / 25 Due : Monday, October 22 2012 11:00 PM EDT The due date for this assignment is past. Your work can be viewed below, but no changes can be made. Important! Before you view the answer key, decide whether or not you plan to request an extension. Your Instructor may not grant you an extension if you have viewed the answer key. Automatic extensions are not granted if you have viewed the answer key. Request Extension View Key 1. 5/5 points | Previous Answers NCSUGenChem102LabV1 8.PRE.01. Green checks and red X's are not displayed for this question. The following items concern safety in the experiment on Equilibrium and Le Châtelier's Principle. Select all appropriate responses for each statement. (a) In the experiment on Le Châtelier's Principle, why must one be very careful when handling concentrated hydrochloric acid (12 M HCl)? (Select all that apply.) Its vapor is a respiratory irritant, so it should be used in a fume hood. It is very expensive, and should not be wasted. It is a known human carcinogen. It is flammable and explosive. It is highly corrosive, and can injure the eyes and skin. (b) If 12 M HCl is splashed onto the eyes or skin, what is the proper response? First: Notify the instructor about the accident. Neutralize the acid with a sodium bicarbonate solution. Flush the affected area with a lot of water. Next: -‐‑Responses/last?dep=4449713 1/5 11/6/12 Lab 8 PreLab -‐‑ Eq. and LeChatelier's Principle Neutralize the acid with a sodium bicarbonate solution. Flush the affected area with some more water. Have your lab partner notify the instructor about the spill while you continue rinsing with water. (c) Why should silver nitrate be handled carefully? (Select all that apply.) It is caustic and corrosive. It is a suspected carcinogen. It will cause dark spots where it contacts the skin. It is toxic. Equilibrium and Le Chatelier's Principle -‐‑Responses/last?dep=4449713 2/5 11/6/12 Lab 8 PreLab -‐‑ Eq. and LeChatelier's Principle 2. 6/6 points | Previous Answers NCSUGenChem102LabV1 8.PRE.02. Green checks and red X's are not displayed for this question. Select all responses which correctly address safety issues in the Equilibrium and Le Châtelier's Principle lab. The usual rules about appropriate clothing and safety glasses must be observed. Food and beverages are never permitted in labs. The usual rules about appropriate clothing can be ignored because we won't be handling chemicals. The usual rules about safety glasses can be ignored because we won't be handling chemicals. While working on the Equilibrium and Le Châtelier's Principle experiment, wastes should be kept in the following way. They should be left in the cuvettes. They should be kept in a labeled beaker at the bench. They should be kept in the dark so they don't degrade. They should be kept in a beaker at the bench. At the end of the Equilibrium and Le Châtelier's Principle experiment, wastes should be disposed of in the following way. They should be flushed down the sink with plenty of water. They should be sent to the cafeteria for recycling. They should be thrown in the trash can. There will be no waste material in this experiment. They should be disposed of in the labeled container. Equilibrium and Le Chatelier's Principle -‐‑Responses/last?dep=4449713 3/5 11/6/12 Lab 8 PreLab -‐‑ Eq. and LeChatelier's Principle 3. 6/6 points | Previous Answers NCSUGenChem102LabV1 8.PRE.03. Green checks and red X's are not displayed for this question. The following items concern equilibrium and Le Châtelier's Principle. Choose the best response. (a) What is a reversible reaction? A reversible reaction is one that shifts only to the left upon the addition of a product. A reversible reaction is one that proceeds in the forward direction when heated. A reversible reaction is one that is under stress. A reversible reaction is one that can proceed in either direction because reactants are not completely used to form products. (b) When is equilibrium established? Equilibrium is established when the reaction is exothermic only. Equilibrium is never established in chemical reactions. Equilibrium is established when the rates of the forward and reverse reactions are equal. Equilibrium is established when a stress is introduced in a reaction. Equilibrium is established when the amount of reactant is equal to the amount of product. (c) What is the effect of raising the temperature of a system at equilibrium? It shifts the equilibrium toward the lower energy side of the equilibrium. It changes the isotopic composition of both reactants and products. It shifts the equilibrium toward the higher energy side of the equilibrium. It causes both the forward and backward reaction to speed up, but has no net effect. Equilibrium and Le Chatelier's Principle -‐‑Responses/last?dep=4449713 4/5 11/6/12 Lab 8 PreLab -‐‑ Eq. and LeChatelier's Principle 4. 8/8 points | Previous Answers NCSUGenChem102LabV1 8.PRE.04. Green checks and red X's are not displayed for this question. (a) Several reactions will be studied in the Equilibrium and Le Châtelier's Principle experiment. Select the correct ones from the list below. (Select all that apply.) 4 NH3(g) + 3 O2(g) NH4Cl(s) 2 N2(g) + 6 H2O(l) NH4+(aq) + Cl –(aq) HCO3–(aq) + H3O+(aq) CO2(g) + H2O(l) CoCl 42–(aq) + 6 H2O(l) Co(H2O)62+(aq) + 4 Cl –(aq) Fe3+(aq) + SCN –(aq) FeSCN2+(aq) (b) Only one of the reactions is heated as part of the experiment. Which is it? 4 NH3(g) + 3 O2(g) NH4Cl(s) 2 N2(g) + 6 H2O(l) NH4+(aq) + Cl –(aq) HCO3–(aq) + H3O+(aq) CO2(g) + H2O(l) CoCl 42–(aq) + 6 H2O(l) Co(H2O)62+(aq) + 4 Cl –(aq) Fe3+(aq) + SCN –(aq) FeSCN2+(aq) (c) Some of the equilibrium reactions will change colors. Select the correct color change for the forward reaction. CoCl 42–(aq) + 6 H2O(l) Fe3+(aq) + SCN –(aq) Co(H2O)62+(aq) + 4 Cl –(aq) goes from blue to pink. FeSCN2+(aq) goes from colorless to red. Equilibrium and Le Chatelier's Principle -‐‑Responses/last?dep=4449713 5/5 ...
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