1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Precision and accuracy of a solution

  1. Apr 5, 2015 #1
    1. The problem statement, all variables and given/known data
    so let's say that we have a solution S=0.4±0.01/250ml
    i want to do a dilution
    so i pick 5ml and pour it into 100ml beaker
    how should i calculate precision of the solution (mathematically or with some other equations)?
    2. Relevant equations
    so basically we have F=5*S/100

    3. The attempt at a solution
    for me 5*S/100=8*10^-5±2*10^-6
    is this true because it doesn't seem right for me (about the pricision)?
     
    Last edited: Apr 5, 2015
  2. jcsd
  3. Apr 5, 2015 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    The relative uncertainty stays the same, that is right.
    You might get an additional uncertainty if the 5ml or the 100ml are not exact.
     
  4. Apr 5, 2015 #3
    so
    so what you say is that no mater how many dilution we do the precision stays the same and it depends on the solution we're using.so it means ±0.01 for all diluted solutions we made,right?
     
  5. Apr 5, 2015 #4

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    The relative uncertainty stays the same.
    It is always 1/40. Roughly speaking, your solution might be 1/40 more concentrated than you thought, or 1/40 less. And that uncertainty does not change if your dilution factors afterwards are known exactly.
     
  6. Apr 5, 2015 #5
    so let's assume that final result is true , so it would be 8*10^-5 ±1/40 and so for all resulting solutions
    and that by using Δy/y
    correct me if I'm wrong
    thanks and sorry for my stubbornness
     
  7. Apr 5, 2015 #6

    Borek

    User Avatar

    Staff: Mentor

    I am afraid you can be sure neither 5 mL nor 100 mL are exact and they are additional sources of error.
     
  8. Apr 5, 2015 #7

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    No, in this case it would be 8*10-5 +- 2*10-6 as the uncertainty is 1/40 of the value.

    With the caveat that the 5ml and 100ml won't be exact, as mentioned.
     
  9. Apr 6, 2015 #8

    Borek

    User Avatar

    Staff: Mentor

  10. Apr 6, 2015 #9
    thank you mfb and Borek for your help
    much appreciated
     
  11. Apr 6, 2015 #10

    Borek

    User Avatar

    Staff: Mentor

    You can use @cham to tag users in the thread.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Precision and accuracy of a solution
Loading...