Q: A 200.0 mg tablet of ibuprofen contains how many molecules of ibuprofen? (Molar mass of ibuprofen = 206.3 g/mol, Avogadro's number = $$6.022 \times 10$$^{23}$$ molecules/mol)

$$5.84 \times 10$$^{20}$$ molecules

Question 1

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

Accepted Answer

Water is a compound, and when elements combine to form compounds, they create entirely new substances with unique properties.

Question 2

Which law states that a chemical compound always contains the same proportion of elements by mass?

Accepted Answer

Law of Definite Proportion

Question 3

What type of bond forms between sodium and chlorine to make table salt (NaCl)?

Accepted Answer

Ionic bond

Question 4

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

Accepted Answer

An empirical formula shows the simplest whole-number ratio of atoms, while a molecular formula shows the actual number of atoms of each element in a molecule.

Question 5

Which of the following is the correct Lewis symbol for silicon (Si)?

Accepted Answer

A symbol with four dots around Si, representing four valence electrons.

Question 6

Which of the following compounds contains a metal with an invariant charge?

Accepted Answer

SrCl$$_2$$

Question 7

What is the correct name for the compound CaBr$$_2$$?

Accepted Answer

Calcium bromide

Question 8

Which of the following best explains why MgO has a higher melting point than NaCl?

Accepted Answer

MgO has higher melting point because the ions have larger charges.

Question 9

Which of the following is the correct formula for the compound formed between aluminum and nitrogen?

Accepted Answer

$$\mathrm{Al_3N_2}$$

Question 10

A sample of a compound is decomposed and produces 24.5 g of nitrogen and 70.0 g of oxygen. What is the empirical formula of the compound? (N: 14.01 g/mol, O: 16.00 g/mol)

Accepted Answer

$$\mathrm{NO_2$}$$

Question 11

Which of the following statements about ionic solids is correct?

Accepted Answer

Ionic solids are brittle and shatter when struck.

Question 12

What is the mass percent of chlorine in Freon-112 ($$\mathrm{C_2Cl_4F_2}$$)? (C: 12.01 g/mol, Cl: 35.45 g/mol, F: 19.00 g/mol)

Accepted Answer

58.6%

Question 13

Which of the following is the correct name for the compound $$\mathrm{N_2O_5}$$?

Accepted Answer

Dinitrogen pentoxide

Question 14

A 200.0 mg tablet of ibuprofen contains how many molecules of ibuprofen? (Molar mass of ibuprofen = 206.3 g/mol, Avogadro's number = $$6.022 	imes 10$$^{23}$$ molecules/mol)

Accepted Answer

$$5.84 	imes 10$$^{20}$$ molecules

Question 15

Which of the following best describes why prefixes such as mono-, di-, and tri- are used in naming molecular compounds but not ionic compounds?

Accepted Answer

Prefixes are used for molecular compounds but not for ionic compounds.

Question 16

Which of the following is the correct molecular formula for a compound with an empirical formula of CH$$_2O $$and a molar mass of 180 g/mol? (Empirical formula mass = 30 g/mol)

Accepted Answer

$$\mathrm{C_6H_{12}O_6$}$$

Question 17

Which of the following statements about the Lewis model of bonding is correct?

Accepted Answer

Lewis structures focus on valence electrons because chemical bonding involves the transfer or sharing of valence electrons.

Question 18

Which of the following is a correct ratio that can be derived from the molecular formula for water ($$\mathrm{H_2O}$$)?

Accepted Answer

2 mol H : 1 mol O

Question 19

Which of the following best explains why ionic compounds conduct electricity when dissolved in water but not in the solid state?

Accepted Answer

In the solid state, ions are locked in place and cannot move; in solution, ions are free to move and carry charge.

Molecules and Compounds: Structure, Bonding, and Formulas

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