Light of three different wavelengths—325 nm, 455 nm, and 632 nm—is shined on a metal surface. The observations for each wavelength, labeled A, B, and C, is as follows: Observation A: No photoelectrons were observed.
Observation B: Photoelectrons with a kinetic energy of 155 kJ/mol were observed
Observation C: Photoelectrons with a kinetic energy of 51 kJ/mol were observed
Which observation corresponds to which wavelength of light?
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Answer:
A. No photoelectrons < C. KE = 51 kJ·mol⁻¹ < B. KE = 155 kJ·mol⁻¹
632 nm < 455 nm < 325 nm
Explanation:
The equation for the photoelectric effect is
E = hf = Φ + KE
That is, the energy (hf) of the incident photon is used to eject an electron from the surface of the metal ( the work function, Φ), and anything left over goes into the kinetic energy (KE) of the electron.
1. Calculate the relative energies of the three wavelengths
E = hf
fλ = c or f = c/λ. So,
E = (hc)/λ
The energy is inversely proportional to the wavelength. Thus, the order of increasing energies is
632 nm < 455 nm < 325 nm
2. Assign the radiation to the observations.
Solve the photoelectric equation for KE.
E = Φ + KE
KE = E - Φ
If E < Φ, the light does not have enough energy to eject a photoelectron.
Once E > φ, the greater the value of E, the greater the value of KE.
The order of energies is
A. No photoelectrons < C. KE = 51 kJ·mol⁻¹ < B. KE = 155 kJ·mol⁻¹
632 nm < 455 nm < 325 nm
Final answer:
Observation A corresponds to the 325 nm wavelength, observation B corresponds to the 632 nm wavelength, and observation C corresponds to the 455 nm wavelength.
Explanation:
The observation labeled A corresponds to the 325 nm wavelength, observation B corresponds to the 632 nm wavelength, and observation C corresponds to the 455 nm wavelength. This is because the behavior of photoelectric effect can be explained by Einstein's equation, E = hf, where E is the energy of a photon, h is Planck's constant, and f is the frequency of the light. Since frequency and wavelength are inversely proportional, higher frequency light corresponds to shorter wavelength and vice versa.
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Skeleton equation →
Balanced equation →
What is a balanced chemical equation?
A balanced equation is an equation for a chemical reaction in which the number of atoms for each element in the reaction and the total charge is the same for both the reactants and the products.
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balanced equation C6H12O6 + 6O2 -----> 6CO2 + 6 H2O
Answers
Answer:
CaCO3 + 2HCL -> CO2 +H2O + CaCl2
Explanation:
When balancing an equation, it is important to first ensure that the chemical formulas in the equation are correct. In the above equation, the first modification required is for CaCl to be corrected to CaCl2. This is because the calcium ion has a charge of 2+ which has to be balanced by 2 chloride ions, each of charge 1-
Next, the overall atoms of the equations should be balanced. The number of atoms of each element on the side of reactants should be equal to their number on the side of the products. In this case, the number of HCL molecules should be 2.
Before balancing equation:
Reactants: Ca: 1, C: 1, O: 3, H: 1, Cl: 1
Products: Ca: 1, C: 1, O: 3, H: 2, Cl: 1
After balancing equation:
Reactants: Ca: 1, C: 1, O: 3, H: 2, Cl: 2
Products: Ca: 1, C: 1, O: 3, H: 2, Cl: 2
:CaCO3+2HCl---> CO2+ H2O+CaCl2