Q: A compound is decomposed to yield 12.0 g of element X and 4.0 g of element Y. What is the mass ratio of X to Y in this compound?

$$\frac{12.0\,\text{g}}{4.0\,\text{g}} = 3.0$$

Q: What is the formula mass of $$\mathrm{Mg(NO_3$)_2}$$? (Atomic masses: Mg = 24.31 amu, N = 14.01 amu, O = 16.00 amu)

$$24.31 + 2 \times 14.01 + 6 \times 16.00 = 148.33\ \mathrm{amu}$$

Q: Which of the following is the correct formula mass for $$\mathrm{$$CCl_4$$}$$? (Atomic masses: C = 12 amu, Cl = 35 amu)

$$1 \times 12 + 4 \times 35.45 = 153.8\ \mathrm{amu}$$

Question 1

Which of the following best illustrates the law of constant composition?

Accepted Answer

Two samples of carbon dioxide from different sources both have an oxygen-to-carbon mass ratio of $$\frac{4.8\,	ext{g O}}{1.8\,	ext{g C}} = 2.7$$

Question 2

A compound is decomposed to yield 12.0 g of element X and 4.0 g of element Y. What is the mass ratio of X to Y in this compound?

Accepted Answer

$$\frac{12.0\,	ext{g}}{4.0\,	ext{g}} = 3.0$$

Question 3

How many total atoms are present in one formula unit of $$\mathrm{Pb($$HSO_4$$)_4}$$?

Accepted Answer

25

Question 4

Which of the following is the correct chemical formula for a compound containing aluminum ions and phosphate ions?

Accepted Answer

$$\mathrm{$$AlPO_4$$}$$

Question 5

Which of the following substances is a molecular element?

Accepted Answer

$$\mathrm{Cl_2$}$$

Question 6

What is the correct name for the compound $$\mathrm{Fe(NO_3$)_3}$$?

Accepted Answer

iron(III) nitrate

Question 7

Which of the following is the correct formula for the compound formed between strontium and chlorine?

Accepted Answer

$$\mathrm{$$SrCl_2$$}$$

Question 8

A sample of water is decomposed to yield 8.0 g of oxygen and 1.0 g of hydrogen. What is the mass ratio of oxygen to hydrogen, and does this support the law of constant composition?

Accepted Answer

The mass ratio is $$8.0:1$$, which supports the law of constant composition.

Question 9

Which of the following is the correct name for $$\mathrm{N_2O_4}$$?

Accepted Answer

dinitrogen tetroxide

Question 10

What is the formula mass of $$\mathrm{Mg(NO_3$)_2}$$? (Atomic masses: Mg = 24.31 amu, N = 14.01 amu, O = 16.00 amu)

Accepted Answer

$$24.31 + 2 	imes 14.01 + 6 	imes 16.00 = 148.33\ \mathrm{amu}$$

Question 11

Which of the following is the correct name for $$\mathrm{H_2SO_3}$$?

Accepted Answer

sulfurous acid

Question 12

Which of the following compounds is best classified as an ionic compound?

Accepted Answer

$$\mathrm{Na_2O}$$

Question 13

What is the correct name for $$\mathrm{K_2CrO_4}$$?

Accepted Answer

potassium chromate

Question 14

Which of the following is the correct formula for iron(III) oxide?

Accepted Answer

$$\mathrm{Fe_2O_3}$$

Question 15

A space-filling model shows two red spheres and two white spheres. According to the color code (red = oxygen, white = hydrogen), what is the correct chemical formula for this compound?

Accepted Answer

$$\mathrm{H_2O_2}$$

Question 16

Which of the following is the correct name for $$\mathrm{HF(aq)}$$?

Accepted Answer

hydrofluoric acid

Question 17

Which of the following best describes the difference between an ionic and a molecular compound?

Accepted Answer

Ionic compounds are composed of cations and anions arranged in a lattice, while molecular compounds are composed of discrete molecules.

Question 18

What is the correct name for $$\mathrm{CO}$$?

Accepted Answer

carbon monoxide

Question 19

Which of the following is the correct formula mass for $$\mathrm{$$CCl_4$$}$$? (Atomic masses: C = 12 amu, Cl = 35 amu)

Accepted Answer

$$1 	imes 12 + 4 	imes 35.45 = 153.8\ \mathrm{amu}$$

Question 20

Which of the following is the correct name for $$\mathrm{$$HClO_3$$}$$?

Accepted Answer

chloric acid

Ch 5: Molecules and Compounds: Structure, Classification, and Nomenclature

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