When an excited electron falls from n = 3 to n = 2, a red radiation in the balmer series emitted. what is the frequency of this photon?
a. 6.63 x 10-34 hz
b. 2.19 x 1016 hz
c. 5.28 x 1011 hz
d. 4.57 x 1014 hz

Awelder using a tank of volume 7.50×10^-2 m^3 fills it with oxygen (with a molar mass of 32.0 g/mol ) at a gauge pressure of 3.30×10^5 pa and temperature of 37.1 ∘c. the tank has a small leak, and in time some of the oxygen leaks out. on a day when the temperature is 23.1 ∘c, the gauge pressure of the oxygen in the tank is 2.00×10^5 pa . a) find the initial mass of oxygen. b) find the mass of oxygen that has leaked out.