Q: Calculate the formula mass of calcium nitrate, Ca(NO$$_3$$)$$_2. ($$Atomic masses: Ca = 40.08, N = 14.01, O = 16.00)

$$40.08 + 2 \times (14.01 + 3 \times 16.00) = 164.10$$ amu

Q: A tablet contains 200.0 mg of ibuprofen (C$$_{13}H$_{18}O$_2). $$How many molecules of ibuprofen are in the tablet? (Molar mass = 206.29 g/mol, $$N_A = 6.022 \times 10$$^{23}$$)

$$\frac{0.2000\ \mathrm{g}}{206.29\ \mathrm{g/mol}} \times 6.022 \times 10$$^{23}$$ = 5.84 \times 10$$^{20}$$ molecules

Question 1

Which of the following statements best explains why water (H$$_2O) $$has very different properties from its constituent elements, hydrogen and oxygen?

Accepted Answer

Water is a compound in which hydrogen and oxygen atoms are chemically bonded in a fixed ratio, resulting in new properties.

Question 2

According to the law of definite proportions, which of the following is true for a sample of pure water?

Accepted Answer

It always contains twice as many hydrogen atoms as oxygen atoms.

Question 3

Which of the following best describes an ionic bond?

Accepted Answer

A bond formed by the transfer of electrons from a metal to a nonmetal, resulting in oppositely charged ions.

Question 4

Which of the following compounds is an example of a molecular compound?

Accepted Answer

CO$$_2$$

Question 5

What is the empirical formula for a compound with the molecular formula C$$_4H$_8$$?

Accepted Answer

$$\mathrm{CH}_2$$

Question 6

Which of the following is the correct name for the compound Fe$$_2(SO$_4$$)$$_3$$?

Accepted Answer

Iron(III) sulfate

Question 7

A sample of a compound contains 24.5 g of nitrogen and 70.0 g of oxygen. What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{N}_2\mathrm{O}_5$$

Question 8

Which of the following best describes why ionic solids, such as NaCl, conduct electricity when dissolved in water but not in the solid state?

Accepted Answer

The ions are locked in place in the solid state but are free to move when dissolved, allowing electrical conductivity.

Question 9

What is the correct formula for the ionic compound formed between aluminum and nitrogen?

Accepted Answer

$$\mathrm{Al}_3\mathrm{N}_2$$

Question 10

Which of the following is the correct name for the compound SnCl$$_2$$?

Accepted Answer

Tin(II) chloride

Question 11

Which of the following is the correct name for the molecular compound N$$_2O$_5$$?

Accepted Answer

Dinitrogen pentoxide

Question 12

Calculate the formula mass of calcium nitrate, Ca(NO$$_3$$)$$_2. ($$Atomic masses: Ca = 40.08, N = 14.01, O = 16.00)

Accepted Answer

$$40.08 + 2 	imes (14.01 + 3 	imes 16.00) = 164.10$$ amu

Question 13

A tablet contains 200.0 mg of ibuprofen (C$$_{13}H$_{18}O$_2). $$How many molecules of ibuprofen are in the tablet? (Molar mass = 206.29 g/mol, $$N_A = 6.022 	imes 10$$^{23}$$)

Accepted Answer

$$\frac{0.2000\ \mathrm{g}}{206.29\ \mathrm{g/mol}} 	imes 6.022 	imes 10$$^{23}$$ = 5.84 	imes 10$$^{20}$$ molecules

Question 14

Which of the following is the correct name for the hydrate MgSO$$_4$$·7H$$_2O$$?

Accepted Answer

Magnesium sulfate heptahydrate

Question 15

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

Accepted Answer

$$\mathrm{(NH}_4)_2\mathrm{SO}_4$$

Question 16

A compound has the empirical formula CH and a molar mass of 78.11 g/mol. What is its molecular formula?

Accepted Answer

$$\mathrm{C}_6\mathrm{H}_6$$

Question 17

Which of the following best describes the difference between a structural formula and a molecular formula?

Accepted Answer

A structural formula shows the arrangement of atoms and bonds, while a molecular formula only shows the number and type of atoms.

Question 18

Which of the following is the correct name for NaNO$$_2$$?

Accepted Answer

Sodium nitrite

Chapter 4: Molecules and Compounds – Structure, Bonding, and Properties

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