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Mass, Volume and Specific Gravity

  1. Oct 21, 2012 #1
    I am trying to solve a question which gives me the volume of a mixture and its specific gravity and the percentage of one of the substances in that mixture by mass(everything else in the mixture is irrelevant). I need to find the mass of that substance but I can't seem to understand what I am doing. From what I understand, to get the amount of the substance in the mixture by mass I need the mass of the solution. I looked up this formula on the internet
    volume = mass/specific gravity
    using this I can find the mass of the mixture which I can use to find the mass of the substance. according to the above formula
    mass = volume * specific gravity
    volume is in gallons and S.G is unitless. this gives me a mass in gallons. At this point I am totally lost since I can't find the mass in mass units unless I have the density. I have never worked with specific gravity before so I don't really know too much about it aside from the fact that its a ratio of densities which doesn't really help me much. So how would I find the mass with the information I'm given?
  2. jcsd
  3. Oct 22, 2012 #2


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    welcome to pf!

    hi wahaj! welcome to pf! :smile:
    the missing information is that specific gravity is always relative to water (unless the question specifies otherwise) …

    so you only need to know the density of water :wink:
  4. Oct 22, 2012 #3


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    Specifically, the specific gravity of a substance is its density divided by the density of water.
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