What is the wavelength of light (in nm) if 1.21x10^21 photons have a total energy of 432 j?

The wavelength is 556 nm.

Energy per photon = 432 J/1.21 × 10²¹ photons = 3.570 × 10⁻¹⁹ J/photon

fλ = c, so f = c/λ

E = hf = (hc)/λ

λ = (hc)/E = (6.626 × 10⁻³⁴ J·s × 2.998 × 10⁸ m·s⁻¹)/3.570 × 10⁻¹⁹ J = 5.56 × 10⁻⁷m =  556 nm

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-