* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Equilibrium
Acid–base reaction wikipedia , lookup
Marcus theory wikipedia , lookup
Asymmetric induction wikipedia , lookup
Hydrogen-bond catalysis wikipedia , lookup
Water pollution wikipedia , lookup
Water splitting wikipedia , lookup
Safety data sheet wikipedia , lookup
Process chemistry wikipedia , lookup
Thermodynamics wikipedia , lookup
Freshwater environmental quality parameters wikipedia , lookup
Baby Gender Mentor wikipedia , lookup
Electrochemistry wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Strychnine total synthesis wikipedia , lookup
Thermodynamic equilibrium wikipedia , lookup
George S. Hammond wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Electrolysis of water wikipedia , lookup
Stability constants of complexes wikipedia , lookup
Lewis acid catalysis wikipedia , lookup
Rate equation wikipedia , lookup
Bioorthogonal chemistry wikipedia , lookup
Chemical reaction wikipedia , lookup
Click chemistry wikipedia , lookup
Chemical thermodynamics wikipedia , lookup
Transition state theory wikipedia , lookup
Stoichiometry wikipedia , lookup
Equilibrium (Do Reactions Ever Really Stop?) Model 1: Reaching Equilibrium: Are We There Yet? Read section 17.4, pages 543 – 545, from your textbook. 1. After reading through this section write and discuss with your lab partner how physical equilibrium and chemical equilibrium compare and contrast. 2. What is an example of a system that involves equilibrium without going through a chemical change? 3. If you filled a container with rubbing alcohol and then sealed the container, how could you tell when equilibrium in the container had been reached? 4. If you had an open container of water, could it reach a state of equilibrium? Explain. 5. How do chemists recognize a system that has reached a state of chemical equilibrium? When writing chemical equations, how do we indicate reactions that come to a state of chemical equilibrium? You and your lab partner work together on #6. 6. Obtain 2 graduated cylinders (both the same size) and 2 beakers. b. Label one of the beakers and cylinders as A and the other as B. c. Fill cylinder “A” a little over half full with water and no water in cylinder “B”. d. Record the volume of water in each cylinder. This will be trial 1. e. Pour ½ of the water from cylinder A into beaker B and 1/3 of the water from cylinder B into beaker A. Yes, I know there is initially no water in cylinder B. f. Pour the water from the beakers into their respective cylinders (in other words water from beaker B goes into cylinder B) g. Record the volume in each cylinder. h. Repeat steps e - g four more times. Keep the water in the cylinders when you finish collecting the data. i. Graph the data using volume versus trial. The graph can be put on the same paper as questions 1 – 4. You will have 2 lines on the same graph (one line for A and one for B). j. Describe what eventually happens to the volume of water in the 2 cylinders. k. What point has now been reached? l. If the cylinders A and B represented the reactants and products in a chemical reaction, which of the cylinders represented the reactants and which would represent the products? Explain how you came to this conclusion. Saying you guessed is not an acceptable answer. Model 2: Disturbing Equilibrium Read section 17.5, pages 545 – 547. Then read section 17.8 pages 554 – 557 about how changing the concentration (the amount of a substance) affects equilibrium, including example 17.4 on pages 557 and 558. Don’t worry about the mathematical calculations shown. Now it is time to apply what you have just read. (Over) 7. You will be disturbing a reaction at equilibrium. To do this you need safety goggles from the lab room. The chemicals and equipment for this are located on the counter in the classroom. a. To start with, you need to get the reaction to equilibrium. To do this, fill a small test tube 2/3 full with an aqueous solution of potassium thiocyanate (KSCN). Then add 10 drops of ferric nitrate, Fe(NO3)3, and mix. Mix by pouring the combined chemicals back and forth between two test tubes. The reaction is now at equilibrium as shown below Fe3+(aq) + SCN1-(aq) Fe(SCN)2+(aq) b. c. d. e. f. g. Often reactions are written with only ions that are actually involved in the reaction. This is why the nitrate and potassium ions have been left off of the equation. These ions that are left off the equation are called spectator ions. Write this equation and below each chemical list the solution color. Pour the mixture from part A into 2 test tubes about 1/3 of the total into each test tube. All 3 test tubes should now have the same amount of solution in them. The third test tube will be used as a comparison when changes are made to test tubes 1 and 2 in parts c through g. To the first test tube add 8 drops of KSCN. Record your observations. Based on the color observed what appears to happen to the amount of Fe(SCN)2+(aq)? Next, add 8 drops of ferric nitrate to the second test tube. Record your observations. Based on the color observed, what appeared to happen to the amount of Fe(SCN)2+(aq)? Now add a few crystals of Na2HPO4 to the first test tube. Nake sure you shake for at least 20 seconds. Record your observations. Based on the color observed, what appeared to happen to the amount of Fe(SCN)2+(aq)? Add 4 drops of AgNO3 to the second test tube. Record your observations. Based on the color observed, what appeared to happen to the amount of Fe(SCN)2+(aq)? Finally, add 8 drops of HCl(aq) to the second test tube. Record your observations. Based on the color observed, what appeared to happen to the amount of Fe(SCN)2+(aq)? 8. As you read in your textbook, changing the amount (or concentration) of a reactant or product will shift an equilibrium reaction in a particular direction. If a substance is removed, the reaction will shift to produce more of the substance to reestablish equilibrium. Likewise, when a substance is added to the reaction, the reaction will shift in a direction to remove some of the substance that was added. For example, in part 6c when the KSCN is added the reaction shifts to form more Fe(SCN)2+(aq), thus removing some of the SCN1- that was added. Use the reaction, for the formation of the ammonia from its elements, listed below to describe which way the reaction will shift when equilibrium in a, b, and c. N2(g) + 3 H2(g) 2 NH3(g) a. Addition of ammonia to the reaction. b. Addition of nitrogen gas. c. Addition of oxygen gas that reacts with the hydrogen gas.