For this problem, we should use the Henry's Law formula which is written below:
P = kC
where
P is the partial pressure of the gas
k is the Henry's Law constant at a certain temperature
C is the concentration
Substituting the values,
1.71 atm = (7.9×10⁻⁴ /atm)C
Solving for C,
C = 2164.56 molal or 2164.56 mol/kgwater
Let's make use of density of water (1 kg/1 m³) and the molar mass of NF₃ (71 g/mol).
Mass of NF₃ = 2164.56 mol/kg water * 1 kg/1 m³ * 1 m³/1000000 mL * 150 mL * 71 g/mol = 23.05 g
