Final answer:
Using Henry's Law, the mass of helium gas that can be dissolved in 1.200 L of water at 25°C and a helium partial pressure of 4.74 atm is about 0.0084 g.
Step-by-step explanation:
The student is asking how to calculate the mass of helium that can be dissolved in water at a given temperature and pressure, using Henry's Law. Henry's Law states that at a constant temperature, the amount of a given gas that will dissolve in a liquid is directly proportional to the partial pressure of that gas above the liquid. The formula to calculate the solubility is given by C = kP, where C is the solubility of the gas in mol/L, k is the Henry's Law constant, and P is the partial pressure of the gas.
To find the mass of helium, we first calculate the molarity of He in water using the provided Henry's Law constant (3.7×10⁻⁴ M/atm) and the partial pressure of He (4.74 atm). The solubility C = 3.7×10⁻⁴ M/atm × 4.74 atm = 1.753×10⁻ mol/L.
To convert molarity into mass, we multiply by the volume of water (1.200 L) and the molar mass of helium (4.00 g/mol). The final mass of He is: 1.753×10⁻ mol/L × 1.200 L × 4.00 g/mol = 0.0083984 g of He. So about 0.0084 g of helium can be dissolved in 1.200 L of water at 25°C and a He partial pressure of 4.74 atm.