Part A Suppose that the microwave radiation has a wavelength of 11.2 c m . How m
ID: 820280 • Letter: P
Question
Part A Suppose that the microwave radiation has a wavelength of 11.2cm . How many photons are required to heat 235mL of coffee from 25.0 ?C to 62.0 ?C? Assume that the coffee has the same density, 0.997g/mL , and specific heat capacity, 4.184J/(g?K) , as water over this temperature range. Express the number of photons numerically. Part A Suppose that the microwave radiation has a wavelength of 11.2cm . How many photons are required to heat 235mL of coffee from 25.0 ?C to 62.0 ?C? Assume that the coffee has the same density, 0.997g/mL , and specific heat capacity, 4.184J/(g?K) , as water over this temperature range. Express the number of photons numerically.Explanation / Answer
Mass of coffee = volume x density = 235 x 0.997 = 234.295 g
Heat required = mass x specific heat x temperature change of coffee
= 234.295 x 4.184 x (62.0 - 25.0) = 36271 J
Wavelength = 11.2 cm = 0.112 m
Energy of 1 photon E = hc/wavelength
= 6.626 x 10^(-34) x 2.998 x 10^8/0.112
= 1.7736 x 10^(-24) J
Number of photons = heat required/energy of 1 photon
= 36271/1.7736 x 10^(-24)
= 2.045 x 10^28 photons = 2.05 x 10^28 photons