Q: A photon has a frequency of $$6.25 \times 10$$^{14}$$\ \mathrm{Hz}. $$What is its wavelength in meters? (Speed of light $$c = 3.00 \times 10^8$\ \mathrm{m/s})$$

$$4.80 \times 10$$^{-7}$$\ \mathrm{m}$$

Q: Calculate the energy of a single photon with a frequency of $$6.25 \times 10$$^{14}$$\ \mathrm{Hz}$$. ($$h = 6.626 \times 10$$^{-34}$$\ \mathrm{J \cdot s})$$

$$4.14 \times 10$$^{-19}$$\ \mathrm{J}$$

Q: If the energy of a photon is $$4.14 \times 10$$^{-19}$$\ \mathrm{J}$$, what is its frequency? ($$h = 6.626 \times 10$$^{-34}$$\ \mathrm{J \cdot s})$$

$$6.25 \times 10$$^{14}$$\ \mathrm{Hz}$$

Question 1

A photon has a frequency of $$6.25 	imes 10$$^{14}$$\ \mathrm{Hz}. $$What is its wavelength in meters? (Speed of light $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$4.80 	imes 10$$^{-7}$$\ \mathrm{m}$$

Question 2

What is the wavelength in nanometers of light with a frequency of $$6.25 	imes 10$$^{14}$$\ \mathrm{Hz}$$? (Speed of light $$c = 3.00 	imes 10^8$\ \mathrm{m/s}$$; $$1\ \mathrm{m} = 10^9$\ \mathrm{nm})$$

Accepted Answer

$$480\ \mathrm{nm}$$

Question 3

Calculate the energy of a single photon with a frequency of $$6.25 	imes 10$$^{14}$$\ \mathrm{Hz}$$. ($$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J \cdot s})$$

Accepted Answer

$$4.14 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 4

What is the total energy in kilojoules of one mole of photons, each with a frequency of $$6.25 	imes 10$$^{14}$$\ \mathrm{Hz}$$? ($$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J \cdot s}$$, $$N_A = 6.022 	imes 10$$^{23}$$\ \mathrm{mol}^{-1})$$

Accepted Answer

$$249\ \mathrm{kJ/mol}$$

Question 5

Which of the following best describes a line spectrum?

Accepted Answer

A spectrum showing only specific, discrete wavelengths of light emitted or absorbed by an element.

Question 6

Why was the hydrogen line spectrum historically significant in the development of atomic theory?

Accepted Answer

It provided evidence that electrons occupy quantized energy levels.

Question 7

According to the Bohr model, what happens when an electron in a hydrogen atom moves from $$n=5 to$$ $$n=2$$?

Accepted Answer

A photon is emitted with energy equal to the difference between the two energy levels.

Question 8

Calculate the wavelength (in nm) of light emitted when an electron in a hydrogen atom transitions from $$n=5 to$$ $$n=2$$. ($$R_H = 1.097 	imes 10^7$\ \mathrm{m}^{-1}$$, $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$434\ \mathrm{nm}$$

Question 9

Which equation correctly relates the energy of a photon to its frequency?

Accepted Answer

$$E = h 
u$$

Question 10

A student claims that the line spectrum of hydrogen is continuous because electrons can have any energy. What is the flaw in this reasoning?

Accepted Answer

Electrons in hydrogen can only occupy specific, quantized energy levels, so only certain transitions (and thus certain wavelengths) are possible.

Question 11

Which of the following best explains why the energy of a mole of photons is much larger than the energy of a single photon?

Accepted Answer

A mole contains Avogadro's number of photons, so the total energy is multiplied by $$6.022 	imes 10$$^{23}$$.

Question 12

Which formula would you use to calculate the wavelength of light emitted during an electron transition in hydrogen from $$n_i to$$ $$n_f$$?

Accepted Answer

$$\frac{1}{\lambda} = R_H \left( \frac{1}{n_f^2$} - \frac{1}{n_i^2$} \right)$$

Question 13

If the energy of a photon is $$4.14 	imes 10$$^{-19}$$\ \mathrm{J}$$, what is its frequency? ($$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J \cdot s})$$

Accepted Answer

$$6.25 	imes 10$$^{14}$$\ \mathrm{Hz}$$

Question 14

Which of the following statements about the Bohr model is correct?

Accepted Answer

Electrons can only occupy certain allowed orbits with fixed energies.

Question 15

A hospital uses a UV lamp emitting light at $$254\ \mathrm{nm} to $$sterilize equipment. What is the energy of one photon of this light? ($$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J \cdot s}$$, $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$7.83 	imes 10$$^{-19}$$\ \mathrm{J}$$

General Chemistry Chapter 2: Light, Energy, and Atomic Structure Practice Guidance

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