Question 1

Which of the following best explains why the second ionization energy of sodium ($$\mathrm{Na}) is $$much higher than its first ionization energy?

Accepted Answer

The second electron is removed from a completely filled shell, which is more stable.

Question 2

Which of the following compounds contains both ionic and covalent bonds?

Accepted Answer

Ammonium sulfate, $$\mathrm{(NH_4$)_2SO_4}$$

Question 3

Which of the following best describes why the formation of an ionic bond between sodium and chlorine is exothermic?

Accepted Answer

The electrostatic attraction between oppositely charged ions lowers the potential energy of the system, as described by Coulomb's Law: $$E = \dfrac{kQ_1Q_2}{r}.$$

Question 4

Which of the following is the correct formula for iron(III) sulfate?

Accepted Answer

$$\mathrm{Fe_2$(SO_4$)_3}$$

Question 5

A sample of $$\mathrm{$$CaCO_3$$} ($$calcium carbonate) has a mass of 50.0 g. What is the number of moles of $$\mathrm{$$CaCO_3$$} in $$the sample? (Molar mass of $$\mathrm{$$CaCO_3$$} = 100.1 g/$$mol)

Accepted Answer

$$0.499$$ mol

Question 6

Which of the following molecules is nonpolar, despite having polar bonds?

Accepted Answer

Carbon dioxide, $$\mathrm{CO_2$}$$

Question 7

Which of the following best explains why ozone ($$\mathrm{O_3$}) $$can absorb UV-B radiation while $$\mathrm{O_2$}$$ cannot?

Accepted Answer

Ozone has resonance structures that allow for delocalized electrons, enabling absorption of UV-B radiation.

Question 8

Given the following mass percent composition: 40.0% C, 6.7% H, and 53.3% O, what is the empirical formula of the compound?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 9

Which of the following statements about sigma ($$\sigma) $$and pi ($$\pi) $$bonds is correct?

Accepted Answer

A double bond consists of one $$\sigma$$ bond and one $$\pi$$ bond.

Question 10

Which of the following best describes the shape and hybridization of methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

Tetrahedral shape with $$sp^3$$ hybridization

Question 11

Which of the following best explains why $$\mathrm{He_2$}$$ does not exist as a stable molecule, according to molecular orbital theory?

Accepted Answer

The number of electrons in antibonding orbitals equals the number in bonding orbitals, resulting in a bond order of zero.

Question 12

Which of the following is the correct name for $$\mathrm{N_2O_4}$$?

Accepted Answer

Dinitrogen tetroxide

Question 13

Which of the following best describes the difference between constructive and destructive interference of atomic orbitals?

Accepted Answer

Constructive interference increases electron density between nuclei, forming a bonding orbital; destructive interference creates a node, forming an antibonding orbital.

Question 14

Which of the following molecules has a central atom with $$sp^2$$ hybridization?

Accepted Answer

Formaldehyde, $$\mathrm{CH_2O}$$

Question 15

Which of the following best explains why lone pairs occupy more space than bonding pairs in VSEPR theory?

Accepted Answer

Lone pairs are localized on one atom and are not shared, so their electron density is closer to the nucleus and repels bonding pairs more strongly.

Question 16

Which of the following is the correct formula for ammonium phosphate?

Accepted Answer

$$\mathrm{(NH_4$)_3PO_4}$$

Question 17

A molecule has the following Lewis structure: the central atom is bonded to three other atoms and has one lone pair. What is the molecular geometry?

Accepted Answer

Trigonal pyramidal

Question 18

Which of the following statements about bond energy and bond length is correct?

Accepted Answer

Triple bonds have higher bond energies and shorter bond lengths than single bonds.

Question 19

Which of the following best describes the role of cis- and trans- isomers in the chemistry of vision?

Accepted Answer

The conversion between cis- and trans- isomers in retinal triggers a signal in the visual process.

Question 20

Which of the following is the correct percent by mass of oxygen in $$\mathrm{H_2SO_4}$$? (Molar mass: $$\mathrm{H_2SO_4} = 98.1 g/$$mol)

Accepted Answer

$$65.0\%$$

Study Guide: Atomic Properties, Chemical Bonding, and Molecular Structure

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