Q: A sample of chlorine contains two isotopes: $$^{35}\text{Cl} (75.8$$% abundance, mass = 34.97 amu) and $$^{37}\text{Cl} (24.2$$% abundance, mass = 36.97 amu). What is the average atomic mass of chlorine?

Average atomic mass = $$0.758 \times 34.97 + 0.242 \times 36.97 = 35.45$$ amu

Q: How many molecules are in 18.0 g of water ($$\text{H}_2\text{O}$$)? (Molar mass of water = 18.0 g/mol, Avogadro's number $$N_A = 6.022 \times 10$$^{23}$$)

Number of molecules = $$\frac{18.0}{18.0} \times 6.022 \times 10$$^{23}$$ = 6.022 \times 10$$^{23}$$

Q: What is the energy of a photon with a wavelength of $$500 nm$$? (Planck's constant $$h = 6.63 \times 10$$^{-34}$$ J·s, speed of light c = 2.998$$ \times $$10^8 m/s)$$

Energy $$E = \frac{hc}{\lambda} = \frac{6.63 \times 10$$^{-34}$$ \times 2.998 \times 10^8$}{500 \times 10$$^{-9}$$} = 3.97 \times 10$$^{-19}$$ J

Question 1

Which of the following best describes the difference between precision and accuracy in a laboratory measurement?

Accepted Answer

Precision refers to how close repeated measurements are to each other, while accuracy refers to how close a measured value is to the true value.

Question 2

A student measures the mass of a liquid as 15.0 g and its volume as 12.5 mL. What is the density of the liquid, and how many significant figures should the answer have?

Accepted Answer

Density = $$\frac{15.0}{12.5} = 1.20 g/mL$$, with 3 significant figures.

Question 3

Which of the following is an example of an intensive property?

Accepted Answer

Density

Question 4

Which experiment led to the replacement of Aristotle's model of matter (earth, air, fire, water) with the atomic theory?

Accepted Answer

The willow tree mass experiment, which showed that most of the mass gained by the tree came from water.

Question 5

Which of the following statements about Rutherford's gold foil experiment is correct?

Accepted Answer

It demonstrated that atoms are mostly empty space, with electrons far from the nucleus.

Question 6

Given the isotope symbol $$^{23}_{11}	ext{Na}$$, how many protons, neutrons, and electrons are present in a neutral atom?

Accepted Answer

Protons: 11, Neutrons: 12, Electrons: 11

Question 7

A sample of chlorine contains two isotopes: $$^{35}	ext{Cl} (75.8$$% abundance, mass = 34.97 amu) and $$^{37}	ext{Cl} (24.2$$% abundance, mass = 36.97 amu). What is the average atomic mass of chlorine?

Accepted Answer

Average atomic mass = $$0.758 	imes 34.97 + 0.242 	imes 36.97 = 35.45$$ amu

Question 8

How many molecules are in 18.0 g of water ($$	ext{H}_2	ext{O}$$)? (Molar mass of water = 18.0 g/mol, Avogadro's number $$N_A = 6.022 	imes 10$$^{23}$$)

Accepted Answer

Number of molecules = $$\frac{18.0}{18.0} 	imes 6.022 	imes 10$$^{23}$$ = 6.022 	imes 10$$^{23}$$

Question 9

Which of the following best describes the photoelectron effect experiment?

Accepted Answer

Electrons are emitted from a metal surface when light of sufficient frequency shines on it.

Question 10

What is the energy of a photon with a wavelength of $$500 nm$$? (Planck's constant $$h = 6.63 	imes 10$$^{-34}$$ J·s, speed of light c = 2.998$$ 	imes $$10^8 m/s)$$

Accepted Answer

Energy $$E = \frac{hc}{\lambda} = \frac{6.63 	imes 10$$^{-34}$$ 	imes 2.998 	imes 10^8$}{500 	imes 10$$^{-9}$$} = 3.97 	imes 10$$^{-19}$$ J

Question 11

Which set of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

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

Question 12

How many d orbitals are present in the $$n=3$$ principal quantum level?

Accepted Answer

5

Question 13

Which of the following best describes Hund's rule as applied to orbital box diagrams?

Accepted Answer

Electrons fill orbitals singly with parallel spins before pairing up.

Question 14

Which element is likely to form a $$+1$$ ion based on its electron configuration and position in the periodic table?

Accepted Answer

Sodium (Na)

Question 15

Which of the following statements about effective nuclear charge ($$Z_{	ext{eff}}) is $$correct?

Accepted Answer

Effective nuclear charge increases from left to right across a period.

Question 16

Which of the following ions is largest in an isoelectronic series: $$	ext{Na}^+$$, $$	ext{Mg}^{2+}$$, $$	ext{Al}^{3+}$$?

Accepted Answer

$$	ext{Na}^+$$

Question 17

Which of the following best describes the uncertainty principle?

Accepted Answer

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

Question 18

Which of the following is a chemical property?

Accepted Answer

Reactivity with oxygen

Question 19

A photon has a frequency of $$6.0 	imes 10$$^{14}$$ Hz. What is its wavelength? (Speed of light c = 2.998$$ 	imes $$10^8 m/s)$$

Accepted Answer

Wavelength $$\lambda = \frac{c}{
u} = \frac{2.998 	imes 10^8$}{6.0 	imes 10$$^{14}$$} = 5.0 	imes 10$$^{-7}$$ m

General Chemistry Study Guide: Chapters E, 1, 2, and 3

Guida di studio - Domande di pratica

Study guide - Flashcard