It will take 409 liters of water to dissolve 1.00 grams of barium sulfate at 20°C
Barium sulfate is almost insoluble in water. At 20°C, only 2.448 x 10^-3 grams will dissolve in 1 liter of water. So take the amount of barium sulfate and divide by its solubility.
1.00 / 2.448 x 10^-3 = 408.49 liters.
Since we only have 3 significant figures, round the result to 3 figures.
409 liters
