I need help on general chemistry?

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Andy

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Warm objects emit electromagnetic radiation in the infra-red regions. Heat lamps employ this principle to generate infra-red radiation. Water absorbs infra-red radiation with wavelengths near 2.80 micrometer. Suppose this radiation is absorbed by the water and converted to heat. A 1.00 L sample of water absorbs infra-red radiation, and its temperature increases from 20.0 Celsius to 30.0 Celsius degree. How many photons of this radiation are used to heat the water?
 
first...energy of 1 photon

E = hc/L

h = plancks constant = 6.626x10^-34 J x s
c = speed of light = 3.00x10^8 m/s
L = wavelength = 2.80 um = 2.80x10^-6 m

calculate E / photon...in J / photon...

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next...
Q = m Cp dT

Q = energy needed to heat water
m = mass water = 1.00L x (1000 mL / L) x (1g / mL) = 1.00x10^3g H2O
Cp = 4.184 J/g°C
dT = 30.0 - 20.0 = 10.0°C

calculate Q.. in J...

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finally..

J x (1 photon / ___ J) = ___ # photons.

.............. ....↑
this is from part 1 above. but it's the reciprocal. right? watch the units. make sure they cancel
 
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