Q: What is the percent composition of nitrogen in N$$_2O$_4$$? (Molar mass: N = 14.01 g/mol, O = 16.00 g/mol)

$$\frac{2 \times 14.01}{2 \times 14.01 + 4 \times 16.00} \times 100 \approx 30.4\%$$

Question 1

Which of the following best describes the difference between a mixture and a compound, as illustrated by the hydrogen and oxygen mixture and water in the first image?

Accepted Answer

A compound has a fixed ratio of elements, while a mixture can have any ratio.

Question 2

Which type of bond is formed when sodium reacts with chlorine to form table salt, as shown in the images?

Accepted Answer

Ionic bond

Question 3

In the formation of NaCl, sodium becomes a cation and chlorine becomes an anion. What is the charge on each ion?

Accepted Answer

Na$$^{+}$$ and Cl$$^{-}$$

Question 4

Which of the following compounds is a molecular compound?

Accepted Answer

CH$$_2O$$

Question 5

What is the empirical formula for C$$_6H$_6$$?

Accepted Answer

CH

Question 6

Which of the following best describes a ball-and-stick molecular model?

Accepted Answer

It represents atoms as balls and bonds as sticks, showing the molecule's shape.

Question 7

According to the octet rule, how many electrons does boron typically have in its valence shell when forming compounds?

Accepted Answer

6

Question 8

Which of the following compounds would you expect to have the greatest lattice energy?

Accepted Answer

MgO

Question 9

What is the correct name for the compound FeS?

Accepted Answer

Iron(II) sulfide

Question 10

Which of the following is the correct formula for potassium oxide?

Accepted Answer

K$$_2O$$

Question 11

What is the formula for the polyatomic ion sulfate?

Accepted Answer

SO$$_4$$^{2-}$$

Question 12

Which of the following best describes a double covalent bond?

Accepted Answer

Two atoms share two pairs of electrons.

Question 13

What is the correct name for the molecular compound N$$_2O$_5$$?

Accepted Answer

Dinitrogen pentoxide

Question 14

An aspirin tablet contains 325 mg of acetylsalicylic acid (C$$_9H$_8O$_4). $$What is the first step to determine the number of molecules in the tablet?

Accepted Answer

Convert grams to moles using the molar mass.

Question 15

What is the percent composition of nitrogen in N$$_2O$_4$$? (Molar mass: N = 14.01 g/mol, O = 16.00 g/mol)

Accepted Answer

$$\frac{2 	imes 14.01}{2 	imes 14.01 + 4 	imes 16.00} 	imes 100 \approx 30.4\%$$

Question 16

A compound is found to contain 43.64% phosphorus and 56.36% oxygen by mass. What is the empirical formula of the compound? (P = 30.97 g/mol, O = 16.00 g/mol)

Accepted Answer

P$$_2O$_5$$

Question 17

If the empirical formula of a compound is CH$$_2O $$and its molar mass is 180 g/mol, what is its molecular formula? (Molar mass of CH$$_2O = 30 g/$$mol)

Accepted Answer

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

Question 18

Which of the following statements about ionic compounds is correct?

Accepted Answer

Ionic compounds are held together by electrostatic attraction between cations and anions.

Question 19

Which of the following is the correct Lewis structure for a water molecule?

Accepted Answer

O atom in the center with two single bonds to H atoms and two lone pairs on O.

Question 20

Which of the following best explains why MgO has a higher lattice energy than NaCl?

Accepted Answer

Mg$$^{2+}$$ and O$$^{2-}$$ have greater charges than Na$$^{+}$$ and Cl$$^{-}$$, leading to stronger electrostatic attraction.

Chapter 4: Molecules and Compounds – Structured Study Notes

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