Final answer:
To determine how much N₂ can dissolve in H₂O at a partial pressure of 0.7 atm, the Henry's Law constant for N₂ is required, which is not provided in the question, thus making it impossible to select the correct option.
Step-by-step explanation:
The amount of gas that can dissolve in water at a certain partial pressure is described by Henry's Law, which states that the solubility of a gas in a liquid at a particular temperature is directly proportional to the pressure of that gas above the liquid. This implies that if the partial pressure of N₂ is 0.7 atm, we need to refer to the Henry's Law constant for N₂ to determine how much of it dissolves in H₂O. Without the Henry's Law constant, we cannot provide a specific value, and none of the options (a) 0.7 atm, (b) 0.3 atm, (c) 1.0 atm, or (d) 0.5 atm can be verified as the correct answer to this question.