5,7% of error in a Hydrated Crystal lab, is it too high?

Last week I had to do a Hydrated Crystal lab with CuSO4 with my class. The purpose was to found the amount of water in one mole of CuSO4.

Theoretically there is 5 mole of water for 1 mole CuSO4. I found 5,29 mole of water for one mole of CuSO4, which give a 5,7 percentage of error. Does it sound reasonable or too high/low. Which percentage of error is acceptable?

1 Answer
Dec 14, 2015


I say your percent error could pass as acceptable.


The thing with percent error is that you don't have a standard interval of accepted values that you can use as a reference for every experiment you do.

Percent error depends on the application itself. More specifically, percent error depends on what measurement limitations your experiment has.

For high school level chemistry labs, a percent error that revolves around #5%# is actually a good result.

Of course, this depends on the requirements set by your instructor.

If your equipment allows for very accurate measurements, your target percent error could go as low as #1-3%#. Otherwise, percent errors of #10-15%# can be considered acceptable as well.

Your values correspond to a #38.169%# water percent composition for copper(II) sulfate pentahydrate. The accepted value is about #36.075%#, so I would say that your results are not ideal, but that they should fall within the accepted range.

Again, that ultimately depends on what your instructor considers acceptable.