chem help..................?

Question

i need to know how to get the answers step by step. all i need is the answere, but i do not know where to begin.

1.Carbon absorbs energy at a wavelength of 150. nm. The total amount of energy emitted by a carbon sample is 5.98 × 105 J. Calculate the number of carbon atoms present in the sample, assuming that each atom emits one photon.


2. An FM radio station broadcasts at 90.2 MHz. Calculate the wavelength of the corresponding radio waves.
i got 9.01 10^7 m

thanx

Answer 1

1) It seems to me that you have trouble to relate energy in J to frequency or wavelength. Please memorize the following formula.
To convert energy to frequency or wavelength, we have to use the following formula:
E = h•ν = h•c/λ
where h the Plank constant 6.626x10^-34 J•s, ν the frequency in 1/s, c the speed of light 2.998x10^8m/s, and λ the wavelength in m (1nm = 10^-9m).
The energy of one photon of wavelength 150. nm is:
E = h•c/λ = (6.626x10^-34 J•s)*(2.998x10^8m/s)/(150.x10^-9m)
= 1.32x10^-18 J
So the final answer is: 5.98 ×10^5 / 1.32x10^-18 = 4.52x10^23

(2) For any wave, the following equation holds:
ν•λ = V
where ν the frequency of wave in 1/s, λ the wavelength of wave in m, and V the speed of wave in m/s. For any electro-magnetic wave (in this case as well), V is the speed of light c = 2.998x10^8m/s. Here ν = 90.2 MHz = 90.2x10^6 /s. Now please do the math: λ = c/ν. Your previous result is toooo large.