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Homework Help: Density Question

  1. Oct 10, 2006 #1
    Hi, here's my problem:

    The balance of a bottle when empty is 70.0g, when full of water is 90.0g and when full of another liquid is 94.0g. The density of water is 1000km/m(to the power of 3), what is the density of the toher liquid?

    I know that density = mass / volume so i think that i should take 70.0 away from 90.0 to get the mass of the water alone, so I get 20.0g. From here I'm stuck. Thanks for any help!
  2. jcsd
  3. Oct 10, 2006 #2
    You know that from the formula of density=mass/ volume.
    You have mass of water and density of water. You can calculate the volume of the bottle that way. I'm sure you can take it from there.
  4. Oct 10, 2006 #3
    Ah yes, so I need to calculate the volume of the bottle.

    I found the volume of the bottle to be 0.02 and thus got the density to be = 24.0 / 0.02 = 1200kg m^3. Could you please clarify that i have done this correctly?
  5. Oct 10, 2006 #4
    should density be shown in kg/l or g/ml
  6. Oct 11, 2006 #5
    That answer is accurate. Very good. However I have to point out an error you have made. You did not convert your mass into kg, hence your volume is actually wrong since your density is in kg/m^3 while your mass cancels out. Make sure all your units are continous.

    Addtionally, try to have a bearing of the quantities you calculate. 0.02 m^3 is very large, 20 litres, compared to the meagre 90 g of water.

    Finally, density in kg/l is valid, however I strongly recommend you use kg/m^3 since that will make both of them SI units. For future questions, converting the units into SI can help you avoid many mistakes.:cool:
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