Finding the mass of the earth's atmosphere

[deltabourne]

A barometer having a cross-sectional area of 1.00 cm^2 at sea level measures a pressure of 76.0 cm of mercury. The pressure exerted by this column of mercury is equal to the pressure exerted by all the air on 1 cm^2 of Earth's surface. Given that the density of mercury is 13.6 g/mL and the average radius of Earth is 6371 km, calculate the total mass of Earth's atmosphere in kilograms (Hint: The surface area of a sphere is 4pir^2)

I have no idea where to start on this one, and how to relate the mercury to find the mass of the atmosphere.. can anyone point me in the right direction?

[Tom Mattson]

I don't think you even need the density of mercury. You know the pressure and the area over which the pressure acts. Since P=F/A, you can determine the force that exerts the pressure (which is the weight of the air above the barometer). That gives you the mass of a column of air with a cross section of 1cm2. To get the mass of the entire atmosphere, you need to use the formula for the area of a sphere that was given.