Q: Chlorine has two naturally occurring isotopes: $$^{35}\mathrm{Cl} (75.78$$%, mass = 34.969 amu) and $$^{37}\mathrm{Cl} (24.22$$%, mass = 36.966 amu). What is the average atomic mass of chlorine?

$$(0.7578 \times 34.969) + (0.2422 \times 36.966) = 35.45\ \mathrm{amu}$$

Q: How many atoms are present in $$2.00\ \mathrm{mol} of $$carbon? (Avogadro’s number $$= 6.022 \times 10$$^{23}$$\ \mathrm{atoms/mol})$$

$$2.00 \times 6.022 \times 10$$^{23}$$ = 1.20 \times 10$$^{24}$$ atoms

Q: If the wavelength of light is $$500\ \mathrm{nm}$$, what is its frequency? (Speed of light $$c = 3.00 \times 10^8$\ \mathrm{m/s}$$, $$1\ \mathrm{nm} = 1 \times 10$$^{-9}$$\ \mathrm{m})$$

$$\nu = \frac{c}{\lambda} = \frac{3.00 \times 10^8$}{500 \times 10$$^{-9}$$} = 6.00 \times 10$$^{14}$$\ \mathrm{Hz}$$

Question 1

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture in which the composition is uniform throughout, such as salt dissolved in water.

Question 2

Which step in the scientific method involves formulating a tentative explanation for an observation?

Accepted Answer

Hypothesis

Question 3

Dalton’s atomic theory states all of the following EXCEPT:

Accepted Answer

Atoms can be created or destroyed in chemical reactions.

Question 4

A sample of magnesium reacts with oxygen to form magnesium oxide. If 24.3 g of magnesium reacts with 16.0 g of oxygen, what is the total mass of magnesium oxide formed? (Law of Conservation of Mass)

Accepted Answer

$$40.3\ \mathrm{g}$$

Question 5

Which experiment provided evidence for the existence of the electron?

Accepted Answer

J. J. Thomson’s cathode ray experiment

Question 6

An atom of $$^{37}\mathrm{Cl}$$ has how many neutrons? (Atomic number of Cl = 17)

Accepted Answer

$$20$$

Question 7

Chlorine has two naturally occurring isotopes: $$^{35}\mathrm{Cl} (75.78$$%, mass = 34.969 amu) and $$^{37}\mathrm{Cl} (24.22$$%, mass = 36.966 amu). What is the average atomic mass of chlorine?

Accepted Answer

$$(0.7578 	imes 34.969) + (0.2422 	imes 36.966) = 35.45\ \mathrm{amu}$$

Question 8

Which technique is commonly used to determine the masses of atoms?

Accepted Answer

Mass spectrometry

Question 9

Convert $$5.00\ \mathrm{g} of $$water to moles. (Molar mass of $$\mathrm{H}_2\mathrm{O} = 18.02\ \mathrm{g/mol})$$

Accepted Answer

$$5.00\ \mathrm{g} \div 18.02\ \mathrm{g/mol} = 0.277\ \mathrm{mol}$$

Question 10

How many atoms are present in $$2.00\ \mathrm{mol} of $$carbon? (Avogadro’s number $$= 6.022 	imes 10$$^{23}$$\ \mathrm{atoms/mol})$$

Accepted Answer

$$2.00 	imes 6.022 	imes 10$$^{23}$$ = 1.20 	imes 10$$^{24}$$ atoms

Question 11

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

Accepted Answer

$$\Delta E = h 
u$$

Question 12

If the wavelength of light is $$500\ \mathrm{nm}$$, what is its frequency? (Speed of light $$c = 3.00 	imes 10^8$\ \mathrm{m/s}$$, $$1\ \mathrm{nm} = 1 	imes 10$$^{-9}$$\ \mathrm{m})$$

Accepted Answer

$$
u = \frac{c}{\lambda} = \frac{3.00 	imes 10^8$}{500 	imes 10$$^{-9}$$} = 6.00 	imes 10$$^{14}$$\ \mathrm{Hz}$$

Question 13

Which of the following observations supports the quantization of energy?

Accepted Answer

The emission of light at specific wavelengths from excited hydrogen atoms

Question 14

What is the significance of the photoelectric effect in the development of quantum theory?

Accepted Answer

It demonstrated that light has particle-like properties and energy is quantized.

Question 15

Arrange the following types of electromagnetic radiation in order of increasing energy: infrared, ultraviolet, visible.

Accepted Answer

Infrared \u003c Visible \u003c Ultraviolet

Question 16

Which electron transition in a hydrogen atom results in the absorption of the highest energy photon?

Accepted Answer

$$n=1 to$$ $$n=2$$

Question 17

Which of the following quantum number sets is NOT allowed for an electron in an atom?

Accepted Answer

$$n=2,\ l=2,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 18

How many angular nodes are present in a $$3p$$ orbital?

Accepted Answer

$$l = 1$$,\ 	ext{so 1 angular node}$

Question 19

Which statement best describes the Heisenberg uncertainty principle?

Accepted Answer

It is impossible to simultaneously know both the exact position and exact momentum of an electron.

Question 20

How many radial nodes are present in a $$4s$$ orbital?

Accepted Answer

$$n - l - 1 = 4 - 0 - 1 = 3$$

General Chemistry Exam 1 Study Guide: Atoms, Atomic Theory, and Quantum Mechanics

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