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Chemistry II Lab Activities

Page history last edited by David Young 6 years, 9 months ago

 

 

Welcome to the Chemistry II lab activities page 

 

All lab activity outlines can be found here.


 

Unit 1 - Matter and Measurement  

(Unit 1 lab activity rubrics are available here)

 

Measurement Lab

Resources

 

 

 

Density of Ethanol Lab

Resources

 

Pre-lab Reminders, Changes, Hints and Tips

 

  1. We used water today - OOPS! 
  2. You are measuring the combined mass of the graduated cylinder and the ethanol.  DON'T WORRY ABOUT THIS!  It will sort itself out later.
  3. USE the eyedropper to assist in volume measurements.
  4. The 50 cm3 graduated cylinder has a manufacturer stated accuracy of ± 0.8 cm3.  Be aware of this when choosing a reasonable uncertainty for the volume measurements you are making. 
  5. Make sure the balance is tared before measuring mass.  Try to use the same balance for all trials.
  6. DO NOT dispose the ethanol down the sink.  It can be carefully poured back into the stock bottles. 
  7. Data table reminders:  A two column table with a descriptive title.  Column headings have units and uncertainty.  Do not recorde units in the table cell with the data.  Data should have consistent precision (all volumes will have the same number of decimal places for example). 
  8. ON A GRAPH 
    • a y-intercept is an indication of a systematic error.  If the graph should pass through the origin, but doesn't, then that is a good sign there is some kind of built in error.
    • if the points all fall on or very close to a best fit line, there is consistency in your measurement - this is an indication of precision.  If some points fall away from the best fit line, this is an indication of random error (and possible outliers) 

 

What to hand in

  • a two column table of volume and (combined) mass data
  • don't forget a suitable caption, headings with units and reasonable uncertainty
  • a graph, with a best fit line
  • analysis to determine an experimental value for density - use the graph and explain the math
  • a % error calculation (accepted value will need to be researched - it is water remember and it does depend on temperature - about 25 oC)
  • a conclusion statement and comment about accuracy
  • identify how the data indicates possible random/systematic errors, lack of precision/accuracy  - what might have caused these issues? 

 

Specific Heat Capacity of Water Lab

Resources

 

 

Pre-lab Reminders, Changes, Hints and Tips

 

  1. You will share kettles with your classmates - you can put more than one sensor in the kettle at a time.
  2. In Logger Pro - use Experiment >> Data Collection to set up the interface.  You will need to change TWO things (1) the LENGTH of time data is collected AND (2) the SAMPLING RATE or how often the temperature is measured.  Mr Young found that it took about 10 minutes for approximately 1 kg of water to begin boiling vigorously.  
  3. DO NOT START COLLECTING DATA UNTIL THE WATER REACHES ABOUT 30 o
  4. DON'T forget to record the volume of water added,  the wattage rating of the kettle AND the barometric (air) pressure.

 

Data Management and Processing

  1. Copy the Logger Pro data to MS Excel in order to quickly calculate and process.  Mr Young will show you this in class. 
  2. Data table reminders:  Column headings have units and uncertainty.  Do not record units in the table cell with the data.  Data should have consistent precision (all values will have the same number of decimal places for example). 
  3. The timer precision on Logger Pro is very high.  For this reason, the uncertainty in time is negligible.  Note this. 
  4. Graph Reminders 
    • the graph you plot will represent TWO different sets of data i) liquid water heating to the b.p.  and ii) the change of state
    • trying to draw only ONE best fit line will likely not satisfy both data sets.  CONSIDER this when plotting 
    • the best data to use to determine specific heat capacity will be between about 30 and 60 o
    • if the points all fall on or very close to a best fit line, there is consistency in your measurement - this is an indication of precision.  If some points fall away from the best fit line, this is an indication of random error (and possible outliers) 

 

What to hand in

  • a table of data and a suitable graph (with best fit line)
  • don't forget a suitable caption, headings with units and reasonable uncertainty
  • ONE example of each calculation unique to this lab activity - for example how did you calculate the total heat added with time 
  • analysis to determine an experimental value for SHC - use the graph and explain the math
  • a % error calculation (accepted value will need to be researched - it is water remember 
  • USE the workpad provided to help prepare the following
    • a paragraph including a conclusion statement, a comment about accuracy, and notes any indication of errors in data
    • discussion about what specific weaknesses or limitations might have caused these errors.  Prioritize in order of significance, and suggest reasonable improvements. 

 
Unit 2 - Mixtures and Solutions

(Unit 2 Lab Activity Rubrics are available here) 

 

Beer's Law Lab

Resources

  • Here is the Beer's Law Simulation Applet

      • note that the absorbance depends on the type of solution, the concentration, the wavelength of light used, and the distance the light has to pass through the solution before measuring
  • Vernier Colorimeter - guide

 

Pre-lab Reminders, Changes and Tips 

  • Only fill the cuvette 3/4 full (too much or too little will not give a valid measurement)
  • It is essential the cuvette is rinsed with distilled water in between measuring the absorbance of different dilutions and the outside of the cuvettes should be wiped clean and dry with a tissue.
  • Handle cuvettes only by the top edge of the ribbed sides.
  • All solutions should be free of bubbles.
  • Always position the cuvette with its reference mark or clear window facing toward the white reference mark at the top of the cuvette slot on the Colorimeter.

 

Data Management and Processing

  • absorbance values typically do not have units but you should provide an uncertainty if possible
  • show how the concentration was calculated for your solution only.  Uncertainty in this value is not required.
  • show on the graph how the concentration of the unknown solution was determined 

 

What to hand in

  • a section that identifies the important variables 
  • a two part procedure (include diagrams if helpful) outlining how to make a solution and how to measure absorbance.  Your procedure will include a list of materials and statements to ensure a fair test (control). 
  • a table of data and a suitable graph (with best fit line) - show how the concentration of only your solution was calculated and use the graph to show how the concentration of the unknown was found
  • don't forget a suitable caption, headings with units and reasonable uncertainties where applicable

 

 

Titration Lab

Resources

 

 

Pre-lab Reminders, Changes and Tips 

  • DON'T FORGET TO ADD INDICATOR
  • Place the flask on a piece of white paper to help see the color change - remember the titration is finished when the solution turns PALE pink

 

Data Management and Processing

  • NaOH and KHP react in a 1:1 ratio.  The balanced equation can be found in the Resources section above.
  • Show one example of how the concentration of NaOH was calculated.  Calculate the average concentration using all 3 trials.  Don't forget uncertainty.
  • Show one example of how the concentration of H2SO4 was calculated.  You will need to know the average concentration of NaOH you determined previously.  Find an average value from the trials you conducted.  Don't forget to include uncertainty. 

 

What to hand in

  • Qualitative observations of the acid and base solutions and what changed during the titration
  • Mass of KPH and initial and final volume readings for each NaOH titration.   
  • Volume of H2SO4 and initial and final volume readings for each H2SO4 titration. 
  • sample calculations 
  • report the NaOH and unknown H2SO4 calculations.  Include a % error calculation for the acid.

 

 

 

 

 

"Education's purpose is to replace an empty mind with an open one

                                                                 Malcolm Forbes

 

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