Error Analysis (For Spring 2020, you do not need to answer #3) 1. What modifications could be made to the procedure to better account for random (indeterminate) errors? 2. List three potential systematic (instrumental, methodological, or personal) errors that could be made in this experiment. (Note: Be specific, systematic errors are in the details. For example, losing your solution because you knocked over the cuvette is not a systematic error - it's a gross one.)

Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Part A: Solution Preparation

  1. Work in pairs.  Wear safety goggles and an apron. 
  2. Connect the temperature probe to Channel 1 of the LabQuest2. The vertical axis has temperature scaled from 0 to 50°C.  To set the horizontal axis (time) to 0 to 1000 seconds, go to the  menu and change the Duration to 1000 seconds.
  3. Wear gloves for this step only, 2.5 M acid can cause burns.  When diluting concentrated acid, pour acid into water, slowly with stirring; never the reverse. HAVE A DILUTION PLAN BEFORE COMING TO LAB.  (Use the concentration values and volume below in the dilution equation to find the volume of stock solution needed to create the dilute solution.)  Using only volumetric glassware, prepare 250.00 mL of approximately 1.0 M HCl solution from the stock HCl solution in the hood (approximately 2.5 M).  The exact concentration for the stock solution must be recorded from the bottle’s label and the exact concentration for the diluted HCl solution must be calculated.

 

Part B:  Heat of Reaction for MgO(s)  +  2 H+(aq)

  1. Place a Styrofoam cup into a 250-mL beaker.  Place the beaker on a stirrer/hotplate.  Using a graduated cylinder, measure out 100.00-mL of the HCl solution created in the step above into the Styrofoam cup.  Suspend a temperature probe from the bars at the back of the lab bench with a clamp.  Place the temperature probe and stir bar in the acid solution in the Styrofoam cup.
  2. Weigh out ~1.0 g MgO.  Record the mass to the nearest milligram.  Caution:  Avoid inhaling MgO dust. Make sure you write down the number of the balance you used as well as the manufacturer name. You should use the same balance for all of your other measurements to ensure consistency as different balances may be calibrated slightly differently which can affect your masses.
  3. Begin stirring.  Click   to begin data collection and obtain the initial temperature, T1.  After 15 seconds at the same temperature, add MgO to the solution.  Continue to stir the cup contents until a maximum temperature, T2, is reached and the temperature starts to drop.  Click   to end data collection.
  4. Examine the initial readings in the Table window (access by clicking on) to determine the initial temperature, T1 and final temperature, T2.  E-mail this data to your lab notebook.
  5. Pour the solution in a 1 L beaker to be neutralized later.

 

Part C:  Heat of Reaction of Mg(s)  +  2 H+(aq)

  1. Caution:  Do not breathe the vapors produced in the reaction.  Repeat Steps 4-7 using approximately 0.5 g of Mg metal instead of MgO.  Record its mass to the nearest milligram.  Use the same digital scale as in Part B to limit calibration errors.
  2. Add the Mg-acid solution to the 1 L beaker used in step 8.

 

Make sure to clear your email address and password of the LabQuest2 so others can’t access your email account. Shutdown the LabQuest2 and not simply put it to sleep. To shutdown the LabQuest2: press the home key, select System → Shut Down → OK.

 

Part D:  Neutralizing the Acidic Solutions

  1. Place about ¼ in. of NaHCO3(s) in the bottom of a clean 1 L beaker, add water until it barely covers the NaHCO3, stir to make a slurry.   Now slowly pour in the diluted acidic solution from steps 8 & 10 and stir.  (Quick pouring will result in uncontrollable foaming and a mess.)  When foaming stops, check the solution with a small piece (< 1 inch) of pH paper.  If pH = 7, the solution is neutral (pH = 7) and it is OK to pour the neutralized solution down the sink.  Na+, Cl– and Mg2+ ions are normally present in tap water and are not harmful to the environment in small amounts.  If the pH of the solution is less than 7, prepare a new slurry and neutralize the solution again in the same manner. Clean workspace and glassware thoroughly before beginning calculations. Write the balanced chemical equation for the reaction of NaHCO3 with HCl so you can see that the products of this reaction do not pose a threat to the environment.
Error Analysis (For Spring 2020, you do not need to answer #3)
1. What modifications could be made to the procedure to better account for random
(indeterminate) errors?
2. List three potential systematic (instrumental, methodological, or personal) errors that could
be made in this experiment. (Note: Be specific, systematic errors are in the details. For
example, losing your solution because you knocked over the cuvette is not a systematic error
- it's a gross one.)
Transcribed Image Text:Error Analysis (For Spring 2020, you do not need to answer #3) 1. What modifications could be made to the procedure to better account for random (indeterminate) errors? 2. List three potential systematic (instrumental, methodological, or personal) errors that could be made in this experiment. (Note: Be specific, systematic errors are in the details. For example, losing your solution because you knocked over the cuvette is not a systematic error - it's a gross one.)
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