[helpingout]

We have been trying to solve this problem for a few hours.  We are coming up with different answers and disagree on how to solve it.  Can anyone help?
The fuel tank in an automobile has a capacity of 11.8 gallons. If the density of gasoline is 42.0lbs/ft3.  What is the mass of fuel in kilograms when the tank is full?
My friend keeps converting to liters but I don't see why?   Any hints?

[mike]

11.8 gallons = 1.577 cu feet

density = mass/volume

therefore: mass = density x volume = 42.0 x 1.577 = 66.234lbs

66.234lbs = 30.043kg

[helpingout]

Thanks, that is the answer we worked out too.  Just were not sure.
Now we are working on another problem.  We DONOT want you to solve it.  But we can't pick out the important information.
A solution to chlorinate a swimming pool contains 7% chlorine by mass.  The ideal chlorine level is 1 ppm (parts by mass).  Assume the density of the chlorine solution is 1.10g/ml and the density of the pool water is 1.00g/ml.  What is the vol. of chlorine solution in liters required to produce a ppm level in a 1.8x10^4 gallon pool.
What we can't figure out is if the 7% is relevant and the ppm is relevant?

[mike]

Yes, you need to use the 7% so you can determine how much of the chlorine solution to use.

You also need the ppm level (1ppm) as this tells you how much chlorine you are trying to end up with in the pool.

[helpingout]

we don't know where to start.

[mike]

Work out how much chlorine there is in the pool. Convert the gallons to litres.

Work out how much of the chlorine solution you would need to add to the pool to make that concentration of chlorine.

[helpingout]

Thanks for your help.  It was my boyfriends problem and I was trying to help him.  He couldn't figure it out before he left.  There were just too many variables and we couldn't figure out what went with what.  He will hopefully get the problem solved in  class tomorrow.  I am curious how it will turn out for him.

[mike]

Ok no problem. Don't forget also that 1 ppm is the same as 1mg/L or 1mg/kg etc