Answer:
There is 4010⁻¹² g (or 4 10⁻¹¹ g) solute in one liter of solution
Explanation:
Concentration measured in very small levels is expressed in terms of ppt i.e. parts per trillion which is the amount (grams) of solute present in a liter (L) volume of solution
\(1 ppt = 1*10^{-12} g\ solute/L\ solution\\\)
The concentration of salt in the aquarium is 40 ppt
This implies that there is 40*10⁻¹² g salt in one liter of the solution
