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Answer 1 · 2017-12-02T14:58:15

(a) #3.37xx10^-19 (J)#
(b) #44.1(J)#
(c) #2.03xx10^5 (J)#

The energy of a photon is #E=hν#, where
#h#: Planck constant(#6.626×10^-34 J*s#)
#ν#: Frequency (#ν=c/λ# Hz)

The frequency of the light(λ=#589# nm=#5.89×10^-7# m) is
#ν= c/λ=(3.00xx10^8 " m/s")/(5.89xx10^-7 " m")=5.09xx10^14# Hz.

(a) #E=hν=5.09xx10^14 Hz **6.626xx10^-34 J*s=3.37xx10^-19 (J)# .

I will solve (c) first and get back to (b) later.

(c) Multiple the energy of a photon by Avogadoro's constant(#N_A=6.02xx10^23 mol^-1#).
#3.37xx10^-19*6.02xx10^23=2.03xx10^5 (J)#

(b) Molar mass of sodium is #23.0# g/mol, and #5.00# mg of #Na# is equal to
#(5.00xx10^-3 g)/(23.0 g*mol^-1)=2.17xx10^-4# mol.

Therefore, the total emitted energy is
#2.03xx10^5 (J*mol^-1) * 2.17xx10^-4 (mol) = 44.1 (J)#.