$$A_{avg} = ($$fraction_1$$ \times $$mass_1$$) + ($$fraction_2$$ \times $$mass_2$$)$$

Question 1

Which of the following statements best describes the difference between a compound and a mixture?

Accepted Answer

A compound has a fixed composition and properties, while a mixture can have variable composition and properties.

Question 2

Which of the following elements is a diatomic molecule in its natural state?

Accepted Answer

Oxygen (O$$_2)$$

Question 3

Given the atomic number ($$Z) $$and mass number ($$A) of an $$atom, which formula correctly calculates the number of neutrons ($$n$$)?

Accepted Answer

$$n = A - Z$$

Question 4

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have delocalized electrons that can move freely throughout the lattice.

Question 5

Which of the following is the correct electron configuration for a neutral sodium atom (Na, $$Z=11$$)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^1$$

Question 6

Which of the following best describes the Law of Definite Proportions?

Accepted Answer

A chemical compound always contains exactly the same proportion of elements by mass.

Question 7

A sample contains 70% chlorine and 30% sodium by mass. Which compound is most likely present?

Accepted Answer

NaCl

Question 8

Which of the following is the correct formula for calculating the average atomic mass ($$A_{avg}) of an $$element with two isotopes?

Accepted Answer

$$A_{avg} = ($$fraction_1$$ 	imes $$mass_1$$) + ($$fraction_2$$ 	imes $$mass_2$$)$$

Question 9

Which of the following elements has the highest electronegativity?

Accepted Answer

Fluorine (F)

Question 10

Which statement about the periodic table is correct?

Accepted Answer

Elements are arranged in order of increasing atomic number.

Question 11

Which of the following is a physical change?

Accepted Answer

Melting ice

Question 12

Which of the following best describes an ionic bond?

Accepted Answer

A bond formed by the transfer of electrons from a metal to a nonmetal.

Question 13

Which of the following is the correct Lewis structure for methane (CH$$_4$$)?

Accepted Answer

A central C atom with four single bonds to four H atoms.

Question 14

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have a full valence shell of electrons.

Question 15

Which of the following is the correct order of increasing atomic radius for the elements Na, Mg, and Al?

Accepted Answer

Al \u003c Mg \u003c Na

Question 16

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

Accepted Answer

$$E = h 
u$$

Question 17

Which of the following best describes the difference between a covalent and an ionic compound?

Accepted Answer

Covalent compounds involve sharing electrons, while ionic compounds involve transferring electrons.

Question 18

Which of the following is the correct electron configuration for a chloride ion (Cl$$^-$$, $$Z=17$$)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^6$$

Question 19

Which of the following elements is most likely to form a cation?

Accepted Answer

Sodium (Na)

Question 20

Which of the following best describes the trend in ionization energy across a period in the periodic table?

Accepted Answer

Ionization energy increases from left to right.

Introduction to Chemistry: Structure, Properties, and Bonding of Matter

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