Q: How many total atoms are present in $2.00$ moles of $\mathrm{NH_3}$? ($N_A = 6.02 \times 10^{23}\ \mathrm{mol}^{-1}$)

$4.82 \times 10^{24}$ atoms$\ (2\ \mathrm{mol} \times 6.02 \times 10^{23}\ \mathrm{mol}^{-1} \times 4\ \mathrm{atoms/molecule})$

Q: A student dissolves $58.5$ grams of $\mathrm{NaCl}$ (molar mass $= 58.5\ \mathrm{g/mol}$) in water. How many formula units of $\mathrm{NaCl}$ are present in the solution?

$6.02 \times 10^{23}$ formula units

Question 1

Which of the following elements has exactly 5 valence electrons in its ground state electron configuration?

Accepted Answer

Nitrogen ($Z=7$)

Question 2

According to the octet rule, which of the following ions is most likely to form when a sodium atom reacts?

Accepted Answer

$\mathrm{Na}^{+}$

Question 3

A magnesium atom ($Z=12$) loses two electrons to form an ion. What is the correct symbol for this ion, and how many electrons does it have?

Accepted Answer

$\mathrm{Mg}^{2+}$, 10 electrons

Question 4

Which of the following correctly names the ionic compound $\mathrm{FeCl_3}$?

Accepted Answer

Iron(III) chloride

Question 5

What is the formula for the ionic compound formed between calcium and phosphate ions?

Accepted Answer

$\mathrm{Ca_3(PO_4)_2}$

Question 6

Which of the following compounds is covalent and not ionic?

Accepted Answer

$\mathrm{CO_2}$

Question 7

How many moles of $\mathrm{H_2O}$ molecules are present in $36.0$ grams of water? (Molar mass of $\mathrm{H_2O} = 18.0\ \mathrm{g/mol}$)

Accepted Answer

$2.0$ moles

Question 8

Which of the following best describes the shape of a methane ($\mathrm{CH_4}$) molecule according to VSEPR theory?

Accepted Answer

Tetrahedral

Question 9

Which of the following molecules is polar due to both its bond polarities and its molecular shape?

Accepted Answer

$\mathrm{H_2O}$

Question 10

A sample contains $3.01 	imes 10^{23}$ molecules of $\mathrm{CO_2}$. How many moles of $\mathrm{CO_2}$ are present? ($N_A = 6.02 	imes 10^{23}\ \mathrm{mol}^{-1}$)

Accepted Answer

$0.50$ moles

Question 11

Which of the following correctly gives the number of bonds typically formed by nitrogen in a molecule, and the number of valence electrons it has?

Accepted Answer

3 bonds, 5 valence electrons

Question 12

What is the correct name for the covalent compound $\mathrm{N_2O_4}$?

Accepted Answer

Dinitrogen tetroxide

Question 13

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity decreases down a group and increases across a period.

Question 14

A transition metal forms a compound with the formula $\mathrm{Fe_2O_3}$. What is the oxidation state of iron in this compound?

Accepted Answer

$+3$

Question 15

Which of the following best explains why $\mathrm{NaCl}$ is an ionic compound while $\mathrm{Cl_2}$ is a covalent compound?

Accepted Answer

$\mathrm{NaCl}$ forms between a metal and a nonmetal, while $\mathrm{Cl_2}$ forms between two nonmetals.

Question 16

How many total atoms are present in $2.00$ moles of $\mathrm{NH_3}$? ($N_A = 6.02 	imes 10^{23}\ \mathrm{mol}^{-1}$)

Accepted Answer

$4.82 	imes 10^{24}$ atoms$\ (2\ \mathrm{mol} 	imes 6.02 	imes 10^{23}\ \mathrm{mol}^{-1} 	imes 4\ \mathrm{atoms/molecule})$

Question 17

Which of the following Lewis structures is correct for carbon dioxide ($\mathrm{CO_2}$)?

Accepted Answer

O=C=O, with each O atom having two lone pairs

Question 18

Which of the following best describes the polarity of $\mathrm{CCl_4}$?

Accepted Answer

Nonpolar molecule with polar bonds

Question 19

A student dissolves $58.5$ grams of $\mathrm{NaCl}$ (molar mass $= 58.5\ \mathrm{g/mol}$) in water. How many formula units of $\mathrm{NaCl}$ are present in the solution?

Accepted Answer

$6.02 	imes 10^{23}$ formula units

Chapter 3 Study Guide: Chemical Bonding, The Mole, and Molecular Structure

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