Question 1

Which of the following statements best explains why the mole is a useful unit in chemistry?

Accepted Answer

It allows chemists to count atoms and molecules by weighing them, since atoms and molecules are too small to count individually.

Question 2

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of CO_2$. How many moles of CO_2$ are present?

Accepted Answer

$$0.50$$ mol

Question 3

Which of the following best describes the difference between isotopes of the same element?

Accepted Answer

They have the same number of protons but different numbers of neutrons.

Question 4

Given the following data for chlorine isotopes: $$^{35}Cl (75.76$$%, 34.969 amu) and $$^{37}Cl (24.24$$%, 36.966 amu), what is the average atomic mass of chlorine?

Accepted Answer

$$35.45$$ amu

Question 5

Which of the following is true about the atomic structure of an atom?

Accepted Answer

Most of the atom's volume is occupied by electrons, while the nucleus is very small and dense.

Question 6

A compound has the empirical formula CH$$_2O $$and a molar mass of $$180.16 g/$$mol. What is its molecular formula?

Accepted Answer

C$$_6H$_{12}O$_6$$

Question 7

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture with uniform composition throughout, such as salt water.

Question 8

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number ($$l)$$

Question 9

Which of the following electron configurations represents the ground state of a neutral oxygen atom?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^4$$

Question 10

Which of the following trends is correct for atomic radius across a period in the periodic table?

Accepted Answer

Atomic radius decreases from left to right across a period.

Question 11

Which of the following ions is isoelectronic with Ne and has the smallest ionic radius?

Accepted Answer

Al$$^{3+}$$

Question 12

Which of the following statements about ionization energy is correct?

Accepted Answer

Ionization energy increases across a period from left to right.

Question 13

Which of the following best explains why NaCl conducts electricity when molten but not when solid?

Accepted Answer

Ions are free to move in the molten state, allowing electrical conductivity.

Question 14

Which of the following best describes the bonding in metallic solids?

Accepted Answer

A lattice of positive metal cations surrounded by a sea of delocalized electrons.

Question 15

Which of the following molecules is expected to have the strongest London dispersion forces?

Accepted Answer

I$$_2$$

Question 16

Which of the following statements about hydrogen bonding is correct?

Accepted Answer

Hydrogen bonding occurs when hydrogen is bonded to F, O, or N.

Question 17

Which of the following best describes the process of chromatography?

Accepted Answer

It separates components of a mixture based on their polarity and solubility.

Question 18

A solution is prepared by dissolving $$0.5$$ mol of NaCl in enough water to make $$1.0 L of $$solution. What is the molarity of the solution?

Accepted Answer

$$0.5 M$$

Question 19

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

Accepted Answer

$$E = h v$$

Question 20

Which of the following best explains why the atomic mass of chlorine is not a whole number?

Accepted Answer

It is the weighted average of the masses of its naturally occurring isotopes.

General Chemistry Foundations: Atoms, Molecules, and Bonding

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