Q: A sample contains 0.50 moles of calcium (Ca). How many atoms of calcium are present in the sample? (Avogadro's number $$N_A = 6.022 \times 10$$^{23}$$ atoms/mol)

$$3.01 \times 10$$^{23}$$ atoms

Q: Which of the following is the correct formula to calculate the energy difference between two energy levels in the hydrogen atom according to Bohr's model?

$$\Delta E = -2.18 \times 10$$^{-18}$$ \left( \frac{1}{n_f^2$} - \frac{1}{n_i^2$} \right) J$$

Q: A student needs to convert 12.0 grams of carbon ($$C) to $$moles. What is the correct calculation? (Atomic mass of $$C = 12.01 g/$$mol)

$$\frac{12.0\ \text{g}}{12.01\ \text{g/mol}} = 1.00\ \text{mol}$$

Q: Which of the following is the correct equation for the kinetic energy of an ejected electron in the photoelectric effect?

$$E_{\text{kinetic}} = h\nu - \phi$$

Question 1

Which of the following best describes the Law of Conservation of Mass?

Accepted Answer

The total mass of reactants and products in a chemical reaction remains constant.

Question 2

A sample contains 0.50 moles of calcium (Ca). How many atoms of calcium are present in the sample? (Avogadro's number $$N_A = 6.022 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$3.01 	imes 10$$^{23}$$ atoms

Question 3

Which of the following is the correct formula to calculate the energy difference between two energy levels in the hydrogen atom according to Bohr's model?

Accepted Answer

$$\Delta E = -2.18 	imes 10$$^{-18}$$ \left( \frac{1}{n_f^2$} - \frac{1}{n_i^2$} ight) J$$

Question 4

If an electron transitions from $$n=4 to$$ $$n=2 in a $$hydrogen atom, what is the sign of $$\Delta E$$ and what does it indicate?

Accepted Answer

$$\Delta E is $$negative; energy is emitted as a photon.

Question 5

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

The azimuthal quantum number $$l$$

Question 6

Calculate the wavelength of an electron moving at $$2.0 	imes 10^6$ m/s. (Use de Broglie's equation: $$\lambda = \frac{h}{mv}$$, h = 6.626$$ 	imes $$10^{-34} J$$·s, $$m = 9.11 	imes 10$$^{-31}$$ kg)

Accepted Answer

$$3.63 	imes 10$$^{-10}$$ m

Question 7

Which of the following statements about atomic mass and isotopes is correct?

Accepted Answer

The atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes.

Question 8

A sample of chlorine contains 75.78% $$^{35}Cl ($$mass = 34.969 amu) and 24.22% $$^{37}Cl ($$mass = 36.966 amu). What is the average atomic mass of chlorine?

Accepted Answer

35.45 amu

Question 9

Which of the following is NOT a criterion that defines a wave?

Accepted Answer

Density

Question 10

Which quantum number specifies the orientation of an orbital in space?

Accepted Answer

Magnetic quantum number $$m_l$$

Question 11

A student needs to convert 12.0 grams of carbon ($$C) to $$moles. What is the correct calculation? (Atomic mass of $$C = 12.01 g/$$mol)

Accepted Answer

$$\frac{12.0\ 	ext{g}}{12.01\ 	ext{g/mol}} = 1.00\ 	ext{mol}$$

Question 12

Which of the following best describes the relationship between the position and momentum of an electron according to Heisenberg's uncertainty principle?

Accepted Answer

The more precisely the position is known, the less precisely the momentum is known.

Question 13

Which of the following is the correct equation for the kinetic energy of an ejected electron in the photoelectric effect?

Accepted Answer

$$E_{	ext{kinetic}} = h
u - \phi$$

Question 14

Which of the following is a correct statement about significant figures in calculations?

Accepted Answer

The final answer should reflect the least number of significant figures from the values used in multiplication or division.

Question 15

Which of the following best explains why the emission spectrum of hydrogen consists of discrete lines?

Accepted Answer

Electrons in hydrogen atoms can only occupy specific energy levels, so transitions between these levels produce photons of specific energies.

Question 16

A photon has a frequency of $$6.0 	imes 10$$^{14}$$ Hz. What is its energy? (h = 6.626$$ 	imes $$10^{-34} J$$·s)

Accepted Answer

$$3.98 	imes 10$$^{-19}$$ J

Question 17

Which of the following is NOT a possible value for the magnetic quantum number $$m_l if$$ $$l = 2$$?

Accepted Answer

$$m_l = 3$$

Question 18

Which of the following best describes the principal quantum number $$n$$?

Accepted Answer

It determines the energy level and relative size of the orbital.

Question 19

Which of the following is a correct statement about the photoelectric effect?

Accepted Answer

Electrons are ejected from a metal surface only if the incident light has a frequency above a certain threshold.

Question 20

Which of the following is the correct relationship for the speed of light $$c$$, wavelength $$\lambda$$, and frequency $$
u$$?

Accepted Answer

$$c = \lambda 
u$$

General Chemistry: Atomic Structure, Quantum Theory, and Fundamental Calculations

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