Procedure:
R = record result
1. Put on your laboratory apron and safety goggles.
2. Label a clean, dry 150 or 250 mL beaker with the letter A and your initials.
3. Find the mass of beaker A on a centigram balance to the nearest 0.01 g. R
4. Determine the mass of beaker A on two additional centigram balances. R
5. Label a second clean, dry 150 or 250 mL beaker the letter B and your initials.
6. Find the mass of beaker B on three different centigram balances as you did with beaker A. R
7. Add 5 to 7 grams of K2SO4 to beaker A.
8. Mass beaker A on three different centigram balances. R
9. Determine the mass of a piece of filter paper on three different centigram balances. R
10. Using a graduated cylinder, add 37 ± 1 ml of distilled water to beaker A. Stir for three minutes.
11. Filter the liquid in beaker A into beaker B. Leave any undissolved potassium sulfate in beaker A.
12. After filtering, fold the filter paper flat and put into beaker A. Put beaker A into the oven or some other place that is hot if there is not enough time for it to air dry.
13. Use a Bunsen burner to flame beaker B and evaporate the liquid.
14. Mass beaker B on three different centigrams. R
Data/Calculations:
Average Mass of Beaker A- 48.55 g 48.54 ± 0.01g
48.55 ± 0.00g
48.55 ± 0.00g
average mass of beaker A- 48.55 ± 0.00g
Average Mass of Beaker B- 49.87g 49.87 ± 0.00g
49.87 ± 0.00g
49.87 ± 0.00g
Average Mass of Beaker B- 49.87 ± 0.00g
Average Mass of Beaker A after K2SO4 is added- 54.89g 54.89 ± 0.00g
54.8946 ± 0.0046g
54.8930 ± 0.0030g
Average Mass of Beaker A after K2SO4 is added- 54.89 ± 0.00g
Mass of K2SO4 added- 6.34 ± 0.00g
Average mass of Beaker A with K2SO4 and H20- 91.37g 91.3770 ± 0.0070g
91.37 ± 0.00g
91.3763 ± 0.0063g
Average mass of Beaker A with K2SO4 and H20- 91.37 ± 0.00g
H2O mass is 36.48 g
Average Mass of funnel
.96g .9663 ± 0.0063g
.9653 ± 0.0053g
.96 ± 0.00g
average mass of funnel- .96g
Beaker A with funnel after dried
Average mass of Beaker A w/stuff
50.10 g 50.10 ± 0.00g
50.1046 ± 0.0046g
50.1032 ± 0.0032g
average mass 50.10 ± 0.00g
mass of funnel and K2SO4 - 1.55 g
Beaker B with just substance left
Average mass
55.72g 55.72 ±0.00g
55.7198 ± 0.0002g
55.7184 ± 0.0016g
average mass– 55.72 ± 0.00g
Amount of K2SO4 left in beaker B at end:
5.85g
Amount of K2SO4 left in beaker A at end:
.59
Total amount of K2SO4 left in the end:
6.44 g of K2SO4
6.34 g of K2SO4 is the starting amount
Percent Error:
1.57%
Analysis/Conclusion:
My percent error was extremely small (actually 100 x smaller) compared to my last lab. I think the reason it was so accurate was because we used tongs the whole time and were careful to not contaminate the chemicals. In the end, I calculated that there was more K2SO4 then I started out with. I think there are two possible explanations for this error. One could be that the balances were did not measure perfectly. Even the inaccuracy to the hundredth of a gram could give some percent error. Another possible reason could be that I did not heat all the water out of the beaker. I could have been weighing not just the beaker and the K2SO4, but the beaker, K2SO4, and some leftover H2O.
