Q: A sample contains $$3.0$$ moles of carbon atoms. How many atoms are present in the sample? (Avogadro's number $$= 6.022 \times 10$$^{23}$$ atoms/mol)

$$1.81 \times 10$$^{24}$$ atoms

Question 1

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

Accepted Answer

A compound consists of two or more elements chemically combined in a fixed ratio, while a mixture is a physical blend of substances.

Question 2

Which of the following is the correct electron configuration for a neutral atom of magnesium (Mg, atomic number 12)?

Accepted Answer

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

Question 3

Which of the following elements is most likely to form a cation with a $$+1$$ charge?

Accepted Answer

Sodium (Na)

Question 4

A sample contains $$3.0$$ moles of carbon atoms. How many atoms are present in the sample? (Avogadro's number $$= 6.022 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$1.81 	imes 10$$^{24}$$ atoms

Question 5

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

Accepted Answer

Metals have loosely held valence electrons that can move freely throughout the structure.

Question 6

Which of the following pairs of elements are in the same group (vertical column) of the periodic table?

Accepted Answer

Na and K

Question 7

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 8

Which of the following is the correct Lewis electron-dot structure for the chloride ion ($$Cl^-$$)?

Accepted Answer

A Cl atom surrounded by 8 dots and a negative sign: $$[:Cl:]^-$$

Question 9

Which of the following best describes the trend in atomic radius across a period from left to right in the periodic table?

Accepted Answer

Atomic radius decreases due to increasing nuclear charge.

Question 10

Which of the following molecules is polar?

Accepted Answer

H$$_2O$$

Question 11

A student mixes $$50.0 g of $$NaCl with $$100.0 g of $$water. Which of the following best describes the resulting mixture?

Accepted Answer

A homogeneous mixture (solution)

Question 12

Which of the following best describes the process of sublimation?

Accepted Answer

A solid changing directly to a gas

Question 13

Which of the following is the correct formula for magnesium chloride?

Accepted Answer

$$MgCl_2$$

Question 14

Which of the following statements about the Bohr model of the atom is correct?

Accepted Answer

Electrons move in fixed orbits around the nucleus with quantized energies.

Question 15

Which of the following elements has the highest electronegativity?

Accepted Answer

Fluorine (F)

Question 16

Calculate the average atomic mass of chlorine if $$^{35}Cl ($$mass = 34.97 amu, abundance = 75.77%) and $$^{37}Cl ($$mass = 36.97 amu, abundance = 24.23%) are present.

Accepted Answer

$$(0.7577 	imes 34.97) + (0.2423 	imes 36.97) = 35.45$$ amu

Question 17

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

Accepted Answer

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

Question 18

Which of the following is a physical change?

Accepted Answer

Melting of ice

Question 19

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

Accepted Answer

They have a complete octet of electrons in their outermost shell.

Question 20

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

Accepted Answer

Na \u003c Mg \u003c Al

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

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