Recall Planck's constant equals 6.63 × 10−34 J·s and the speed of light is 3.00 × 108 m/s. Calculate the wavelength (in nm) of a photon emitted by a hydrogen atom when its electron drops from the n = 5 state to the n = 3 state.

The wavelength of light is 1281.9 nm

Explanation:

To calculate the wavelength of light, we use Rydberg's Equation:

Where,

= Wavelength of radiation

= Rydberg's Constant  =

= Upper energy level = 3

= Lower energy level = 5

Putting the values in above equation, we get:

Converting this into nanometers, we use the conversion factor:

So,

Hence, the wavelength of light is 1281.9 nm

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g

1.solid

2.carbon dioxide

3.helium