Question 1

Which of the following best describes the law of conservation of mass?

Accepted Answer

In a chemical reaction, matter is neither created nor destroyed.

Question 2

A log burns completely in a campfire, leaving behind much less mass in the form of ash. According to the law of conservation of mass, what happened to the rest of the matter?

Accepted Answer

The matter that composed the log reacts to form gases that are released into the air.

Question 3

Which of the following is an example of the law of definite proportions?

Accepted Answer

The decomposition of 18.0 g of water always results in 16.0 g of oxygen and 2.0 g of hydrogen, regardless of the water's source.

Question 4

If the mass ratio of nitrogen to hydrogen in ammonia is 4.7:1, how many grams of nitrogen are present in a sample containing 10.0 g of hydrogen?

Accepted Answer

$4.7 	imes 10.0 = 47$ g

Question 5

Which statement best distinguishes the law of definite proportions from the law of multiple proportions?

Accepted Answer

The law of definite proportions applies to two or more samples of the same compound, while the law of multiple proportions applies to two different compounds containing the same two elements.

Question 6

Which experiment led to the discovery of the electron?

Accepted Answer

J.J. Thomson's cathode ray tube experiment

Question 7

What was the key finding of Rutherford’s gold foil experiment?

Accepted Answer

Most of the atom's mass and all of its positive charge are contained in a small core called a nucleus.

Question 8

Which subatomic particle has a mass of approximately $1.67493 	imes 10^{-27}$ kg and no electrical charge?

Accepted Answer

Neutron

Question 9

How many protons, electrons, and neutrons are present in an atom of $^{53}\mathrm{Cr}$?

Accepted Answer

Protons: 24, Electrons: 24, Neutrons: 29

Question 10

Which element contains 50 protons in its nucleus?

Accepted Answer

Tin

Question 11

An argon isotope has a mass number of 40 ($A = 40$) and an atomic number of 18. How many neutrons does it contain?

Accepted Answer

$40 - 18 = 22$

Question 12

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 13

How many electrons are present in the $O^{2-}$ anion?

Accepted Answer

10

Question 14

Which terms best apply to lead (Pb)?

Accepted Answer

Main-group element; metal

Question 15

Which group in the periodic table contains elements that are very reactive nonmetals and tend to gain one electron to form 1- ions?

Accepted Answer

Halogens (Group 7A)

Question 16

Which of the following best describes the periodic law as formulated by Mendeleev?

Accepted Answer

When the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically.

Question 17

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

Accepted Answer

Elements are listed in order of increasing atomic number.

Question 18

A sample of chlorine contains 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu). What is the atomic mass of chlorine?

Accepted Answer

$0.7577 	imes 34.97 + 0.2423 	imes 36.97 = 35.45$ amu

Question 19

How many atoms are present in 2.00 mol of carbon?

Accepted Answer

$2.00 	imes 6.022 	imes 10^{23} = 1.2044 	imes 10^{24}$ atoms

Question 20

Which of the following statements about main-group elements and their ions is correct?

Accepted Answer

Main-group metals tend to lose electrons to form cations with the same number of electrons as the nearest noble gas.

Atoms and Elements: Foundations of Atomic Theory

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