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

$$40.08 + 2 \times 14.01 + 6 \times 16.00 = 164.10 g/$$mol

Q: A 200.0 mg tablet of ibuprofen (C$$_{13}H$_{18}O$_2) $$contains how many molecules? (Molar mass = 206.29 g/mol, Avogadro's number = $$6.022 \times 10$$^{23}$$)

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

Question 1

Which of the following statements best explains why water (H$$_2O) is a $$compound and not a mixture?

Accepted Answer

Water molecules are composed of two hydrogen atoms and one oxygen atom in a fixed ratio.

Question 2

Which type of chemical bond involves the transfer of electrons from one atom to another, resulting in the formation of cations and anions?

Accepted Answer

Ionic bond

Question 3

What is the empirical formula for a compound with the molecular formula C$$_4H$_8O$_4$$?

Accepted Answer

CH$$_2O$$

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 compounds contains a type two cation (a metal with variable charge)?

Accepted Answer

FeCl$$_3$$

Question 6

What is the correct name for the compound FeS?

Accepted Answer

Iron(II) sulfide

Question 7

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

Accepted Answer

Ions are locked in place in the solid state but are free to move when dissolved.

Question 8

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

Accepted Answer

$$40.08 + 2 	imes 14.01 + 6 	imes 16.00 = 164.10 g/$$mol

Question 9

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? (N = 14.01 g/mol, O = 16.00 g/mol)

Accepted Answer

NO$$_2$$

Question 10

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

Accepted Answer

A symbol with four dots around Si

Question 11

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

Accepted Answer

MgO has ions with larger charges, leading to stronger electrostatic attraction.

Question 12

What is the correct name for the compound P$$_2O$_5$$?

Accepted Answer

Diphosphorus pentoxide

Question 13

A 200.0 mg tablet of ibuprofen (C$$_{13}H$_{18}O$_2) $$contains how many molecules? (Molar mass = 206.29 g/mol, Avogadro's number = $$6.022 	imes 10$$^{23}$$)

Accepted Answer

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

Question 14

Which of the following is a correct ratio derived from the molecular formula for water, H$$_2O$$?

Accepted Answer

2 mol H : 1 mol O

Question 15

Which of the following best explains 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 because the same elements can combine in multiple ratios, but not for ionic compounds because their ratios are fixed by charge balance.

Question 16

A compound has an empirical formula of CH$$_2O $$and a molar mass of 180.16 g/mol. What is its molecular formula?

Accepted Answer

C$$_6H$_{12}O$_6$$

Question 17

Which of the following is a polyatomic ion?

Accepted Answer

NO$$_3^-$$

Question 18

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 19

Which of the following is the correct name for the compound Na$$_2SO$_4$$·10H$$_2O$$?

Accepted Answer

Sodium sulfate decahydrate

Molecules and Compounds: Structure, Bonding, and Formulas

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