Question

Suppose that the microwave radiation has a wavelength of 10.8 cm. How many photons are required to heat 225 mL of coffee from 25.0*C to 62.0*C ? Assume that the coffee has the same density, 0.997 g/mL , and specific heat capacity, 4.184 J/(gK), as water over this temperature range

Answer 1

Calculate q required to heat the water for the coffee.
q = mass x specific heat x (Tfinal-Tinitial). q = ?? joules.

How many joules do we get out of 1 photon at this wavelength.
E = hc/wavelength = 6.626 x 10^-34 x 3 x 10^8/wavelength in meters.

Then set up a proportion:
(1 photon/energy 1 photon) = (# photons/energy needed)
Solve for # photons. Check the proportion after it is set up to make sure it is right.

Answer 2

thank you :D