Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Crucible and Oily fingers

  1. Feb 23, 2012 #1
    1. The problem statement, all variables and given/known data

    The crucible is handled with oily fingers after its mass measurement but before the ~3 gram sample of the hydrated salt is measured. Subsequently(after measuring the hydrated salt,the oil is burned off. How does this technique error affect the reported % water in the hydrated salt. Explain

    3. The attempt at a solution
    The measurement of the crucible will be accurate, but after touching the crucible with the oily fingers, it will contaminate the surface of the crucible. After weighing the hydrated surface and then burning the crucible, it will seem that more water was lost because the oily fingers would have increased the mass of the hydrated salt.

    I'm kind of having second thoughts on my answer....part of my mind thinks it will no be affected? HELP!
  2. jcsd
  3. Feb 24, 2012 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Your initial response is correct, now convince yourself of it to make sure you understand. Take it one step at a time to determine where the error is. If it helps, make up a number for the mass of the oily fingerprint so you can track its effect quantitatively.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook