Q: What is the mass percent of oxygen in water ($$\mathrm{H_2O}$$)? (Atomic masses: H = 1.01 g/mol, O = 16.00 g/mol)

$$\displaystyle \frac{16.00}{18.02} \times 100\% = 88.8\%$$

Question 1

Which of the following best describes the difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the transfer of electrons from a metal to a nonmetal, while covalent bonds involve the sharing of electrons between two nonmetals.

Question 2

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

Accepted Answer

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

Question 3

Which of the following compounds is named correctly?

Accepted Answer

NaCl: sodium chloride

Question 4

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

Accepted Answer

$$\mathrm{(NH_4$)_2SO_4}$$

Question 5

What is the mass percent of oxygen in water ($$\mathrm{H_2O}$$)? (Atomic masses: H = 1.01 g/mol, O = 16.00 g/mol)

Accepted Answer

$$\displaystyle \frac{16.00}{18.02} 	imes 100\% = 88.8\%$$

Question 6

A compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 7

Which of the following bonds is the most polar?

Accepted Answer

$$\mathrm{H-F}$$

Question 8

Which molecule violates the octet rule?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 9

Which of the following is a correct resonance structure for the nitrate ion ($$\mathrm{NO_3$^-}$$)?

Accepted Answer

One N=O double bond and two N–O single bonds, with the negative charge delocalized over the two single-bonded oxygens.

Question 10

According to VSEPR theory, what is the molecular geometry of $$\mathrm{NH_3$}$$?

Accepted Answer

Trigonal pyramidal

Question 11

What is the bond angle in a molecule with tetrahedral electron geometry?

Accepted Answer

$$109.5^\circ$$

Question 12

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

Accepted Answer

$$\mathrm{CO_2$}$$

Question 13

Which of the following is the correct hybridization for the central atom in $$\mathrm{BF_3$}$$?

Accepted Answer

$$sp^2$$

Question 14

A molecule has a central atom with two bonding pairs and two lone pairs. What is its molecular geometry and hybridization?

Accepted Answer

Bent, $$sp^3$$

Question 15

Which of the following is the correct name for $$\mathrm{P_2O_5}$$?

Accepted Answer

Diphosphorus pentoxide

Question 16

A sample of a compound contains 0.60 g of C, 0.10 g of H, and 0.80 g of O. What is the empirical formula?

Accepted Answer

$$\mathrm{C_2H_4O}$$

Question 17

Which of the following ions is a polyatomic ion?

Accepted Answer

$$\mathrm{SO_4$^{2-}}$$

Question 18

Which of the following best explains why $$\mathrm{H_2O} is a $$polar molecule?

Accepted Answer

The molecule has a bent shape and the O–H bonds are polar, resulting in a net dipole moment.

Question 19

Which of the following molecules has a central atom with $$sp^3d$ hybridization?

Accepted Answer

$$\mathrm{$$PCl_5$$}$$

Question 20

A patient is given a medication containing sodium bicarbonate. What is the correct formula for this compound?

Accepted Answer

$$\mathrm{$$NaHCO_3$$}$$

Study Guide: Molecules, Compounds, Molecular Shapes, and Valence Bond Theory

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