Question

1.) Calculate the energy difference (?E) for the electron transition of n = 3 to n = 2 for 1.00 mol of hydrogen atoms. Enter your answer in scientific notation.

2.) A lithium flame has a characteristic red color due to emissions of wavelength 671 nm. What is the mass equivalence of 1.0 mol of photons of this wavelength

(1 J = 1 kg·m²/s²)?

------ × 10^------- kg (Enter your answer in scientific notation.) -> the dotted lines are the empty spaces that need to be filled in

Please help I am really lost, I got 3.0297385 x 10^-19 J/mol for the first problem but it was marked wrong, and I have no idea how to solve number 2

Answer 1

1)

Apply Rydberg Formula

E = R*(1/nf^2 – 1/ni ^2)

R = -2.178*10^-18 J

Nf = final stage/level

Ni = initial stage/level

E = Energy per unit (i.e. J/photon)

E = (-2.178*10^-18)*(1/1^3 – 1/2 ^2)

E = 1.6335*10^-18 J/particle

for 1 mol

E = (1.6335*10^-18)(6.022*10^23) = 983693.7 J per mol

2)

WL = 671 nm = 671*10^-9 m

find the mass equivalence

E = m*C^2

solve for E first

E = hc/WL

h = Planck Constant = 6.626*10^-34 J s

c = speed of particle (i.e. light) = 3*10^8 m/s

E = (6.626*10^-34)(3*10^8)/( 671*10^-9) = 2.9624*10^-19 J/particle

E = (2.9624*10^-19)(6.022*10^23) = 178395.728 J/mol

then

E = m*c^2

m = E/(c^2) = 178395.728/(3*10^8)^2 = 1.98217*10^-12 kg