
math water problem
"you have a 55 gallon fish tank, which you want to keep at 34.5 ppt. How many kg of seasalt should you add?"
I can't figure this problem out and any help anyone could give would be much appreciated. thanks.
also, there is a follow up question associated with this: "if 3 gallons of water evaporate from the tank, what is the salinity now?"

Re: math water problem
Well, it's strange that the problem mixes gallons and kg, liters would be nicer. I'm guessing a mass fraction ratio for the problem (mass of salt:mass of water)?
55 gallons converts to 208 litres of water, which means 208 kg of water.
therefore: 208 kg * 34.5 * 10^12 parts ~= 0.000000007176 kg of salt. (7.18 * 10^9 kg)
then for the follow up you do the mass of salt divided by the new mass of water, 52 gallons > 197 kg
7.18 * 10^9 kg / 197kg = 3.64 *10^11 > 36.4 parts per trillion
hope this helps.

Re: math water problem
thanks very much. this was helpful.