1. Convert gallons to mL. 1 gal = 3785.4117840007 mL, multiply that by 29 and get 109776.94173602 mL.
2. Since there is one gram per every mL, there are 109776.94173602 g of water in the fish tank.
3. Convert g to pounds. 1 g = 0.0022 pounds. Multiply 109776.94173602 by 0.0022 and end up with about 241.5 pounds of water.
Ba3PO4 is not neutral, it is positive. (NH4)2SO4 is neutral, the charges cancel.
Mg2OH is not neutral, it is positive. LiF2 is not neutral, it is negative. CaOH is not neutral, it is positive. The answer is (NH4)2SO4, correct ions will have a neutral charge.