Q: Which of the following is the correct calculation for the average atomic mass of chlorine, given $$75.77\%$$ chlorine-35 ($$34.97\ \mathrm{amu}) $$and $$24.23\%$$ chlorine-37 ($$36.97\ \mathrm{amu}$$)?

$$(0.7577 \times 34.97) + (0.2423 \times 36.97)$$

Q: What is the mass, in grams, of $$3.25$$ moles of ammonia ($$\mathrm{NH_3$}$$)? (Molar mass of $$\mathrm{NH_3$} = 17.03\ \mathrm{g/mol})$$

$$3.25 \times 17.03 = 55.3\ \mathrm{g}$$

Q: Which of the following is the correct definition of a mole?

The amount of substance containing $$6.022 \times 10$$^{23}$$ particles.

Q: Which of the following is the correct relationship for converting grams of an element to number of atoms?

$$\text{grams} \xrightarrow{\div\ \text{molar mass}} \text{moles} \xrightarrow{\times\ 6.022 \times 10$$^{23}$$} \text{atoms}$$

Question 1

Which of the following best describes the Law of Conservation of Mass as demonstrated by the reaction: $$7.7\ \mathrm{g}$$ sodium reacts with $$11.9\ \mathrm{g}$$ chlorine to produce $$19.6\ \mathrm{g}$$ sodium chloride?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 2

Which Greek philosopher argued that matter was continuous and could be divided infinitely?

Accepted Answer

Aristotle

Question 3

A sample of mercuric oxide decomposes to produce $$92.61\ \mathrm{g}$$ mercury and $$7.39\ \mathrm{g}$$ oxygen from $$100.00\ \mathrm{g} of $$mercuric oxide. Which law does this experiment best illustrate?

Accepted Answer

Law of Conservation of Mass

Question 4

Which statement is NOT part of Dalton’s Atomic Theory?

Accepted Answer

Atoms can be created and destroyed in chemical reactions.

Question 5

Which law is illustrated by the fact that water ($$\mathrm{H_2O}) $$always contains hydrogen and oxygen in a mass ratio of approximately $$1:8$$, regardless of the source?

Accepted Answer

Law of Definite Proportions

Question 6

Carbon and oxygen can form both carbon monoxide ($$\mathrm{CO}) $$and carbon dioxide ($$\mathrm{CO_2$}). If$$ $$1\ \mathrm{g} of $$carbon combines with $$1.33\ \mathrm{g} of $$oxygen in CO and $$2.67\ \mathrm{g} of $$oxygen in CO$$_2$$, what law does this illustrate?

Accepted Answer

Law of Multiple Proportions

Question 7

Which of the following is the correct calculation for the average atomic mass of chlorine, given $$75.77\%$$ chlorine-35 ($$34.97\ \mathrm{amu}) $$and $$24.23\%$$ chlorine-37 ($$36.97\ \mathrm{amu}$$)?

Accepted Answer

$$(0.7577 	imes 34.97) + (0.2423 	imes 36.97)$$

Question 8

How many moles of $$\mathrm{CO_2$}$$ are present in $$150.0\ \mathrm{g} of$$ $$\mathrm{CO_2$}$$? (Molar mass of $$\mathrm{CO_2$} = 44.01\ \mathrm{g/mol})$$

Accepted Answer

$$\frac{150.0}{44.01} = 3.41\ \mathrm{mol}$$

Question 9

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 10

What is the mass, in grams, of $$3.25$$ moles of ammonia ($$\mathrm{NH_3$}$$)? (Molar mass of $$\mathrm{NH_3$} = 17.03\ \mathrm{g/mol})$$

Accepted Answer

$$3.25 	imes 17.03 = 55.3\ \mathrm{g}$$

Question 11

Which of the following is the correct definition of a mole?

Accepted Answer

The amount of substance containing $$6.022 	imes 10$$^{23}$$ particles.

Question 12

Which property is defined by the atomic number ($$Z) of an $$element?

Accepted Answer

The number of protons in the nucleus.

Question 13

A sample of neon contains $$90.48\%$$ atoms with $$10$$ neutrons, $$9.25\%$$ with $$12$$ neutrons, and $$0.27\%$$ with $$11$$ neutrons. What does this data illustrate?

Accepted Answer

Natural abundance of isotopes.

Question 14

Which of the following best explains why Mendeleev left gaps in his periodic table?

Accepted Answer

He predicted the existence of undiscovered elements.

Question 15

Which of the following is the correct relationship for converting grams of an element to number of atoms?

Accepted Answer

$$	ext{grams} \xrightarrow{\div\ 	ext{molar mass}} 	ext{moles} \xrightarrow{	imes\ 6.022 	imes 10$$^{23}$$} 	ext{atoms}$$

Question 16

Which of the following is a real-world application of the Law of Definite Proportions?

Accepted Answer

Silver sulfide ($$\mathrm{Ag_2S}) $$always forms with a $$2:1$$ ratio of Ag to S, regardless of the source.

Question 17

If $$1.0\ \mathrm{mol} of $$copper atoms has a mass of $$63.55\ \mathrm{g}$$, what is the mass of a single copper atom in amu?

Accepted Answer

$$63.55\ \mathrm{amu}$$

Question 18

Which of the following best describes the periodic law?

Accepted Answer

Elements with similar properties recur in a regular pattern.

Question 19

A tablespoon of water contains approximately $$1\ \mathrm{mol} of $$water molecules. How many molecules is this?

Accepted Answer

$$6.022 	imes 10$$^{23}$$

Atoms, Atomic Theory, and the Periodic Table: Foundations of Chemistry

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