posted by Shylo on .
Please help me with this question from my homework package
What is the minimum number of photons with wavelength 645nm needed to prepare 135 grams of glucose?
When the thermochemical equation is
C6H12O6(s)+ 6O2(g)--> 6CO2(g)+ 6H2O(g) Reaction is -2539.01 Kj/mol
How much energy is needed for a photon of 645 nm? That is delta E = hc/wavelength - 6.626 x 10^-34*3 x 10^8/645 x 10^-9 = about 3 x 10^-19 J/photon (but you need to do this exactly).
How much energy is needed to prepare 135 g glucose? That will be 135/180 (you need to convert the molar mass exactly since my 180 is an estimate) = about 0.75 mol glucose so 0.75 x 2539.01 x 10^3 J/mol = about 1904 J.
So how many packets of energy of 3 x 10^-19 do you need to have a total of 1904 J? Check my work.