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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