chemistry help needed

Question

PLEASE HELP!! I'm so confused.

1. Use the equation for the energy of the electron in the Bohr model of the atom and the fact that hxR = 2.180e-18 J to calculate the energy of an electron in the given level of each of the following ions.

He1+ when n=3

O7+ when n=5

2. a) What is the energy of the n = 2 level of a H atom?

b) What is the energy of the n = 3 level of a H atom?

c) What is E for the n = 2 to n = 3 transition

3. What is the energy in joules of a photon with a frequency of 7.94e+12 s-1? What is the energy in kilojoules of a mole of photons of this frequency? Express you answers to three significant digits.

4. A hydrogen atom in an excited state emits a photon of frequency ν = 3.199 x 1015 s-1. If the electron returns to the ground state, in which level was it before the photon was emitted?

5. How many moles of Fe3O4 can be produced when 6.00 mol Fe react with 2.00 mol O2? How many moles of each reactant are left over? Note that at least one must disappear.

Answer 1

1.) Bohr equation: En = - hR(Z²/n²) and -hR = -2.18x10^-18 J

For He¹⁺, Z = 2 and n = 3:

En = - 2.18x10^-18 (4/9) = -9.7x10^-19 J

Do the same for O⁷⁺ and for the others with varying values of n

2.) For transition from 1 quantum level to another, use 1/λ = RZ2 (1/nf2 - 1/ni2) where λ is wavelength = ?, R is Rydberg, Z = atomic number, nf = final level, ni = initial level and solve for λ. Then use E = hc/λ where h = plancks constant and c = speed of light and solve for E

3.) E = hν where h= plancks constant and ν is frequency. Answer will be in joules

4.) Similar to #2 above, but in reverse

5.) Write the balanced equation: 3Fe + 2O₂ ==> Fe₃O₄. Find limiting reactant: 6 moles Fe vs. 2 mole O₂. O₂ is limiting, Hopefully you can figure out why. Moles Fe3O4 produced = 1 b/c it is half of moles O₂ present from balanced eq. You should be able to figure moles Fe left over. There will be NO moles O_2 left over since it is used up.