Answer : The partial pressure of nitrogen gas is, 2.94 atm
Explanation:
According top the Henry's Law, the concentration of a gas in a liquid is directly proportional to the partial pressure of the gas.


is Henry's constant.
or,

where,
= initial concentration of gas = 
= final concentration of gas = 
= initial partial pressure of gas = 0.78 atm
= final partial pressure of gas = ?
Now put all the given values in the above formula, we get the final partial pressure of the gas.


Therefore, the partial pressure of nitrogen gas is, 2.94 atm