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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: echonet on October 09, 2007, 09:37:53 PM

Title: Simple density problem giving me difficulty :(
Post by: echonet on October 09, 2007, 09:37:53 PM

Here's what I have to solve, easy right?:

"A full barrel holds 750 pounds of gasoline. The same barrel holds 1100 pounds of water when full. What is the density of the gasoline?"

I've go 2 problems with this:
  1. The density of water varies with temperature, right? Do you see any temperature
   anywhere in that question?

  2. The units are strange (pounds). Are there different densities for pounds?

I've done it without worrying about these things (using .99 for density and ignoring the unit conversions that I might need completely), and I got .68. Is this even near right?

Thanks a lot in advance for your help, don't worry this is not for homework!

Title: Re: Simple density problem giving me difficulty :(
Post by: AWK on October 10, 2007, 12:44:58 AM

Pounds are units of mass but not a density.
http://en.wikipedia.org/wiki/Density

Title: Re: Simple density problem giving me difficulty :(
Post by: Padfoot on October 10, 2007, 01:59:05 AM

From the relative difference between the 2 masses you can work out the density of gasoline using density of water=1gmL^-1.

Density water/Density gasoline=m(water)/m(gasoline)
(Since volume is constant)

Density gasoline=m(gasoline)/m(water)*Density water

Title: Re: Simple density problem giving me difficulty :(
Post by: Borek on October 10, 2007, 03:34:32 AM

Ignore temperature, assume water density is 1 g/mL. In genmeral you are right that the question should state in what temperature it all happens. But for all practical purposes water is 1.0 g/mL regardless of temp.