Question

On a clear day at sea level, the partial pressure of N2 in air is 0.78 atm at 25 ºC. Under these conditions, the concentration of N2 in water is 5.3 x 10–4 M. What is the partial pressure of N2 when the concentration in water is 1.1 x 10–3 M?

Answer 1

May I get a formula hint?

Answer 2

\[pV=nRT\]
U can use the ideal gas equation as shown above.. p = pressure, V = volumina, n = moles, T = temperature in K and R = 8.314 J/(mol*K)

Answer 3

But that will not give me partial pressure for that molarity.

Answer 4

For that molarity, I only know n, V, but no T.

Answer 5

Are you saying to assume constant T?

Answer 6

That wouldn't work.

Answer 7

I would assume T = 25°C, there are no other indications in the text.

Answer 8

http://www.cramster.com/answers-may-11/chemistry/partial-pressure-concentra-clear-day-sea-level-temperature-25-degree_1305806.aspx?rec=0

Answer 9

Use Henery's Law P=K x where P is partial pressure and x is mole fraction. Convert molarity into mole fraction.
Molarity=moles/Volume. (Volume od solution assuming water to be 1kg/L you get 5.3 *10^-4 moles in 1kg or 5.3*10^-4 moles in 1000/18 moles of water. From this you get mole fraction.) From the first equation P=k x you know P you know x find K or the Henry's constant.
Now again find mole fraction in second case and substitue in the equation the K value to get the answer. I don't think you want the entire solution, If you have doubts in what i have posted feel free to ask.

Answer 10

PV=nRT is clearly wrong here, (number of moles n is dissolved in liquid whereas Pressure given in pressure of Nitrogen above the liqquid, They are two different things in two different places so do not use PV=nRT)