If a sample of calcium chloride is introduced into a nonluminous ...

Question

If a sample of calcium chloride is introduced into a nonluminous 
flame, the color of the flame turns to orange 
('flame test'). The light is emitted because calcium atoms 
become excited; their return to the ground state results in 
light emission. (b) What is the energy of 
1.00 mol of these photons (a mole of photons is called an 
Einstein)?

Accepted Answer

Hey everyone in this example, we're told lithium chloride in parts of red color to a flame, calculate the energy of one mole of photons if involved, If the wavelength of light emitted is 6 70.8 nanometers, we're going to recall that our formula for the energy of a photon is equal to plank's constant, multiplied by the speed of light. And then we're dividing by our wavelength. We're going to recall that because our units of speed of light should be in meters per second. We're going to have our wavelength be in units of meters so that meters can cancel out. So getting into our calculation for energy of a photon, we would have planks constant, which we recall is 6.626 times 10 to the negative 34th power jewels. Time seconds as the units multiplied by the speed of light, which we recall is 3.0 times 10 to the eighth power meters per second. We're then going to divide by our wavelength given in the prompt as 670.8 nm, which as we said, we would convert to meters. So we're going to recall that our prefix nano tells us that we have 10 to the negative ninth power meters. Now we're able to cancel out nanometers. We can also go ahead and cancel out meters as well as seconds with inverse seconds, leaving us with jewels as our final unit for energy, which is what we want. And we're going to get that energy is equal to a value of 2.963 times 10 to the negative 19th power units of joules per photon. Now, because the prompts us to calculate energy for one mole of our photons, we're going to start out with our energy. We calculated above 2.963 times 10 to the negative 19th power jewels per photon. And we're going to get moles into our setup here by recalling avocados number which we recall in terms of photons is six point oh 22 times 10 to the 23rd Power Photons Permal. So we're able to cancel out photons and we're left with jewels per mole. So what we're going to get for our final answer is a value of 1.785 times 10 to the fifth power and this is jules for one more of photons. So this would be our final answer to complete this example. I hope that everything I reviewed was clear. If you have any questions, please leave them down below and I will see everyone in the next practice video

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