Q: Using the Bohr model, what is the energy change ($$\Delta E) $$when an electron in a hydrogen atom transitions from $$n=3 to$$ $$n=2$$? Use $$R_H = 2.18 \times 10$$^{-18}$$\ \mathrm{J}.$$

$$\Delta E = -2.18 \times 10$$^{-18}$$ (\frac{1}{2^2$} - \frac{1}{3^2$})$$

Question 1

Which of the following best describes a compound?

Accepted Answer

A pure substance composed of two or more different elements that are chemically combined.

Question 2

Which property is intensive and does NOT depend on the amount of substance present?

Accepted Answer

Density

Question 3

A student mixes sand and salt in a beaker. Which type of matter is formed?

Accepted Answer

Heterogeneous mixture

Question 4

Which of the following is a chemical property?

Accepted Answer

Flammability

Question 5

Which experiment led to the discovery that most of the atom is empty space and that the nucleus is small and dense?

Accepted Answer

Rutherford gold foil experiment

Question 6

What is the atomic number of an atom with 8 protons, 8 neutrons, and 8 electrons?

Accepted Answer

8

Question 7

Which of the following best describes the difference between a physical and a chemical change?

Accepted Answer

A chemical change produces a new substance, while a physical change does not.

Question 8

Which of the following is an example of a homogeneous mixture?

Accepted Answer

Salt water

Question 9

Which equation correctly relates the speed of light ($$c$$), wavelength ($$\lambda$$), and frequency ($$
u$$)?

Accepted Answer

$$c = \lambda 
u$$

Question 10

A sample of gasoline has a density of $$0.74\ \mathrm{g/mL}. If $$you have $$200\ \mathrm{mL} of $$gasoline, what is its mass?

Accepted Answer

$$148\ \mathrm{g}$$

Question 11

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 12

Which of the following is the correct formula for calculating the energy of a photon?

Accepted Answer

$$E = h
u$$

Question 13

Using the Bohr model, what is the energy change ($$\Delta E) $$when an electron in a hydrogen atom transitions from $$n=3 to$$ $$n=2$$? Use $$R_H = 2.18 	imes 10$$^{-18}$$\ \mathrm{J}.$$

Accepted Answer

$$\Delta E = -2.18 	imes 10$$^{-18}$$ (\frac{1}{2^2$} - \frac{1}{3^2$})$$

Question 14

Which of the following best explains why boiling water to produce steam is a physical change?

Accepted Answer

The state of water changes but the molecules remain H$$_2O.$$

Question 15

Which of the following is a correct statement about the Bohr model of the atom?

Accepted Answer

Electrons travel in specific, quantized orbits around the nucleus.

Question 16

A neutral atom has 17 protons and 18 neutrons. What is its mass number?

Accepted Answer

35

Question 17

Which of the following is an example of a chemical change?

Accepted Answer

Iron rusting

Question 18

Which of the following best describes an allotrope?

Accepted Answer

Different molecular forms of the same element

Question 19

Calculate the wavelength (in nm) of light emitted when an electron in a hydrogen atom drops from $$n=4 to$$ $$n=1$$ using the Rydberg equation: $$\frac{1}{\lambda} = \frac{1}{91\ \mathrm{nm}} (\frac{1}{n_f^2$} - \frac{1}{n_i^2$}).$$

Accepted Answer

$$\lambda = 97.2\ \mathrm{nm}$$

Atoms, Elements, and Compounds: Foundations of Matter and Atomic Structure

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