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Chem Lab Help

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Trial #1 Trial #2 Trial #3
Mass: gelatin capsule (g) .123 .118 .122
Mass: whole alka-seltzer tablet (g) 3.230 3.230 3.230
Mass: capsule + alka-seltzer sample (g) .822 .882 .677
Mass: system before reaction (g) 23.109 23.110 22.735
Mass system after reaction (g) 21.742 21.813 21.500
Temperature (°C) 21.9 22.1 22.4
Pressure (mmHg) 778 778 778
Volume of water collected (mL) 76.3 78.1 77.3

Answer the following questions using the data you collected in the lab:

Trial #1 Trial #2 Trial #3
Calculate the mass (g) of alka-seltzer in each capsule :

Trial #1 Trial #2 Trial #3
Calculate the mass (g) of NaHCO3 reacted in each sample :
Trial 1 Trial 2 Trial 3
Calculate the percent mass of NaHCO3 in each sample (%):
Trial 1 Trial 2 TRial 3

I wanted to know how to approach these problems.

  • Chem Lab Help -

    Tyler, you don't seem to understand that we can't help when we don't know what you have done. I see all of that data but I have no idea what you did experimentally. If you will write the procedure as well as the data PERHAPS someone can help. I suppose we could simply ignore your question but then it might appear we don't want to help and I thought you deserved an answer explaining why you received no help.

  • Chem Lab Help -

    Carefully clean and dry a 150 mL beaker, a 250 mL beaker, and a large 155mm test tube.
    Remove two Alka-Seltzer tablet from their hermetically sealed packet and weight them.
    Use a clean (use paper towels only, NO water) mortar and pestle to grind the tablets into a fine power.
    Accurately weigh an empty gelatin capsule. Note: make sure your hands are dry and that you close the bottle containing the capsules IMMEDIATELY! Gelatin starts dissolving when it comes in contact with moisture.
    Take the capsule apart and use your scoopula to fill the larger portion with your powdered Alka-Seltzer.
    Put the two parts of the capsule back together, carefully blow off any power than may be sticking to the outside and reweigh.
    Add a magnetic stir bar to your test tube and place it upright in your 150 mL beaker. Use a repipetter to add 10.0 mL of 6M HCl to the test test.
    Weigh the beaker, test tube, stir bar and HCl.
    Fill your water bottle to about half an inch below the 'full line' with distilled water and place it on the magnetic stirrer motor.
    Weigh your clean, dry 250 mL beaker.
    Place it on a your iron ring with the wire gauze, and position it so it can catch all of the water from the water bottle.
    Remove the top from your water bottle and place the test tube/stir bar/HCl in the bottle, it should float.
    Quickly drop the Alka-Seltzer filled gelatin capsule into the test tube and seal the water bottle. Be sure that the top is on tight or some of the carbon dioxide will escape. Make sure the spout of the water bottle is pointed into the 250 mL beaker.
    Now adjust the magnetic stirrer motor to agitate the capsule and HCl. It may take a minute or two for the capsule to dissolve and the reaction to begin.
    As the reaction proceeds you should see a 'foam' produced. At the same time, water will be displaced from the water bottle into the 250 mL beaker.
    Keep adjusting the rate of the magnetic stirrer up and down for about 10 minutes or until all of the 'foam' has disappeared and no more water is being generated.
    After the reaction is complete, weigh the 250 mL beaker. By difference, you now have the mass of water generated.
    Open the water bottle and carefully remove the test tube/stirrer/HCl. Use a paper towel to wipe off any water from the outside of the test tube.
    Place the test tube upright in the same 150 mL beaker and reweigh. By difference, you now have the mass of CO2 generated.
    Record the temperature of the water in the bottle (to 0.1°C). You can use a C.R.C. or this Table of Water Density to find the density of water at this temperature. You will use this to convert the grams of water you obtained in Step #19 into mL. This is the volume of CO2 generated.
    Record the barometric pressure in the lab (How to read an Eco-Celli barometer).
    Clean the test tube thoroughly to remove any remnants of the gelatin capsule. Rinse with distilled water and thoroughly dry with paper towels.
    Repeat Step #4-22 until you have at least four GOOD trials. You can perform a simple calculation to determine if a given trial is 'good' or not. Calculate the amount of water generated by subtracting (c) from (f) and then divide by the mass of CO2 generated, (n). This value should be in the range of 500-600 and should not vary by more than 10-20 units from trial to trial. If it does, you have made some mistakes and will have to run additional trial(s).

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