Question 1

Which ancient philosopher argued that all matter is composed of four elements—earth, air, fire, and water—and that matter is continuous and infinitely divisible?

Accepted Answer

Aristotle

Question 2

Which law states that during a chemical change, matter is neither created nor destroyed, and the total mass of the products equals the total mass of the reactants?

Accepted Answer

Law of Conservation of Mass

Question 3

A sample of methane ($$\mathrm{CH_4$}) is $$decomposed to give carbon and hydrogen in a mass ratio of 3:1. How many grams of hydrogen can be obtained from 90.0 g of methane?

Accepted Answer

$$22.5\ \mathrm{g}$$

Question 4

Which scientist is credited with the Law of Definite Proportions, stating that a compound always contains the same elements in the same proportions by mass?

Accepted Answer

Proust

Question 5

Which of the following best explains why Dalton’s atomic theory was considered a theory and not a law?

Accepted Answer

It explained observed laws and made predictions about the nature of matter.

Question 6

Which of the following is NOT a postulate of Dalton’s atomic theory?

Accepted Answer

Atoms can be created or destroyed in chemical reactions.

Question 7

Which law is illustrated by the fact that carbon and oxygen can form both carbon monoxide ($$\mathrm{CO}) $$and carbon dioxide ($$\mathrm{CO_2$}$$), with different mass ratios of oxygen to carbon?

Accepted Answer

Law of Multiple Proportions

Question 8

A compound contains 40.0 g of calcium and 16.0 g of oxygen. What is the mass ratio of calcium to oxygen in this compound?

Accepted Answer

$$2.5:1$$

Question 9

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes are atoms of the same element with different masses due to different numbers of neutrons.

Question 10

How many atoms are in 2.00 moles of carbon-12?

Accepted Answer

$$1.204 	imes 10$$^{24}$$

Question 11

What is the molar mass of water ($$\mathrm{H_2O}$$)?

Accepted Answer

$$18.0\ \mathrm{g/mol}$$

Question 12

Which scientist arranged the elements in order of increasing atomic mass and predicted the properties of undiscovered elements?

Accepted Answer

Mendeleev

Question 13

Which of the following best describes a molecule?

Accepted Answer

A group of atoms chemically bonded together

Question 14

Which of the following is an example of green chemistry?

Accepted Answer

Replacing rare or hazardous substances with more abundant or less hazardous ones

Question 15

If you have 36.0 g of water ($$\mathrm{H_2O}$$), how many moles do you have? (Molar mass of $$\mathrm{H_2O} is$$ $$18.0\ \mathrm{g/mol})$$

Accepted Answer

$$2.0$$ moles

Question 16

Which of the following statements about the periodic table is correct?

Accepted Answer

Mendeleev arranged elements by increasing atomic mass and left gaps for undiscovered elements.

Question 17

A chemical reaction produces 92.61 g of mercury and 7.39 g of oxygen from 100.00 g of mercuric oxide. Which law does this experiment illustrate?

Accepted Answer

Law of Conservation of Mass

Question 18

Which of the following is a real-world application of the Law of Conservation of Mass?

Accepted Answer

Converting hazardous waste into less harmful substances

Question 19

Which of the following best explains why pure water always freezes at $$0^\circC $$and boils at $$100^\circC at $$sea level?

Accepted Answer

Water is a compound with a constant composition and properties.

Question 20

Which of the following is the correct value for Avogadro’s number?

Accepted Answer

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

Atoms, Laws of Chemical Combination, and the Periodic Table: Foundations of Modern Chemistry

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