Posted by kelsie on .
Enormous numbers of microwave photons are needed to warm macroscopic samples of matter. A portion of soup containing 177 g of water is heated in a microwave oven from 20degrees Celsius to 98 degrees Celsius, with readiation of wavelength 1.55x10^2m. How many photons are absorbed by the water in the soup?

chemistry 
DrBob222,
Calculate q for the heat required to heat the soup.
q = mass x specific heat H2O x delta T.
q = ?? in Joules.
Then use E = hc/wavelength to determine the energy per photon. Go from there. Post your work if you get stuck. Check my thinking. 
chemistry 
Sam,
ok. whew. just put in my answer into webassign and i got it correct.
Ill show the example with the numbers I was given. That way you can actually do the problem with your numbers.
I found the way to do this at the link below.
so my water mass was 360 g
my temp went from 28C to 93C
the radiation of wavelength is 1.55 x 102 m (same)
k so the first thing to do is find the work needed.
Q=mcΔT
this is mass times (4.184J/g°C) ΔT. so (360)(4.184)(9328) = 97905.6 J. The 4.184 changes things to Angstroms. The overall equation will have the units Joules.
k so we also have the equations
E'=hv and c=λv
h = 6.626 x 10^34
c = 3 x 10^8
solve and replace so that somehow you get this
Q (97905.6 J) / (hc/1.55 x 10^2)
so 97905.6/((6.626e34)(3e8)/(1.55e2))
I got 7.6e27
webassign verified it. 
your mom 
Anonymous,
its so easy