Answer:
Using Henry's law, we know that solubility is directly proportional to pressure:
S1/P1 = S2/P2
where S1 and P1 are the initial solubility and pressure, and S2 and P2 are the new solubility and pressure.
Plugging in the values given:
16.9 g/L / 5.00 atm = S2 / 3.00 atm
Solving for S2:
S2 = 10.14 g/L
Therefore, the solubility of the gas at 20 °C and 3.00 atm pressure is 10.14 g/L.