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

Homework Help: Moles in a Cat?

  1. Sep 6, 2004 #1
    I have to approximately figure out, to the nearest order of magnitude, how many moles of atoms there are in a 12 kg cat.You are also told that The masses of a hydrogen atom, an oxygen atom, and a carbon atom are 1.0 u, 16 u, and 12 u. .

    all i know is that 1 u=1.66 x 10^-27 kg.
    From here I am unsure where to go.
  2. jcsd
  3. Sep 6, 2004 #2
    1 mole contains an Avogadro's amount of atoms (Avogadro's no = 6.022 x 10^23), that should help you a bit.
  4. Sep 6, 2004 #3
    Yes I knew that before working on this problem and yet I'm still lost.
  5. Sep 6, 2004 #4
    In what proportion are the main ingrediants found in the cat (ie cat's are 80% water). If you know the mass the proportion of the three elements then you should eb able to find number of moles of atoms.
  6. Sep 6, 2004 #5
    I have no other information besides what I wrote before.
  7. Sep 6, 2004 #6
    Then make some assumptions or do some research. How much water is in a cat? Once you know that you can 'assume' the rest or a portion of the rest is carbon. Once you know how much water is in a cat and the mass of the cat you can easily calculate the moles og H and O. Once you make your assumption about C then you'll be able to calculate the number of C atoms.
  8. Sep 8, 2004 #7

    The above link says: "...Water comprises from about 95 percent of the new-born kitten to about 75 percent of the adult cat..."

    So you have H and O....maybe an estimate is in order?

    Im having difficulty with the same problem ;-). I PMed you GingerBread27 with a question FYI :-). Best of luck.
  9. Sep 8, 2004 #8
    k, i just did the problem myself....follow me...

    H= 1.0u
    O= 16.0u
    C= 12.0u

    we don't know the age of the kitten so lets say roughtly 80% of the given cat is water

    in my version of the problem, my cat is 5 kg....therefore

    80% x 5 kg = 4 kg = amount of H20

    convert to grams.....(habit from chemistry)

    4kg = 4000g

    4000gH20 x (1 mol H20/ 18g H20) = 222 mol H20

    we have 1 kg of the 'cat' unallocated therefore let the remaining carbon equal the 1 kg

    1000gC x (1 mol C / 12g C) = 83.3 mol C

    total 'molage' => 222+83 = 305 mol

    and i was told by my school online software that this was correct. hope this helps...if i made a mistake i apologize - its 1:40 am! Cheerz.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook