Q: A sample contains 75.37% $$^{35}Cl ($$atomic mass 34.969 u) and 24.63% $$^{37}Cl ($$atomic mass 36.966 u). What is the average atomic mass of chlorine?

$$(0.7537 \times 34.969) + (0.2463 \times 36.966) = 35.45 u$$

Question 1

Which experiment provided evidence that most of the mass of an atom is concentrated in a tiny, positively charged nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 2

Which subatomic particle has a mass of $$9.109382 	imes 10$$^{-31}$$ kg and a charge of -1.602176$$ 	imes $$10^{-19} C$$?

Accepted Answer

Electron

Question 3

What is the atomic number ($$Z) of an $$atom with 79 protons?

Accepted Answer

$$Z = 79$$

Question 4

Which statement about isotopes is correct?

Accepted Answer

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

Question 5

A sample contains 75.37% $$^{35}Cl ($$atomic mass 34.969 u) and 24.63% $$^{37}Cl ($$atomic mass 36.966 u). What is the average atomic mass of chlorine?

Accepted Answer

$$(0.7537 	imes 34.969) + (0.2463 	imes 36.966) = 35.45 u$$

Question 6

Which law states that the total mass of reactants equals the total mass of products in a chemical reaction?

Accepted Answer

Law of conservation of mass

Question 7

What is the charge of an atom with 79 protons and 79 electrons?

Accepted Answer

0 (neutral)

Question 8

Which real-world application uses isotope ratios to determine the year of birth from tooth enamel?

Accepted Answer

Forensic dating using $$^{14}C $$levels

Question 9

Which process is illustrated by the splitting of $$^{235}U $$after neutron absorption, releasing energy and forming $$^{92}Kr $$and $$^{141}Ba$$?

Accepted Answer

Nuclear fission

Question 10

Which instrument is used to separate isotopes based on their mass-to-charge ratio?

Accepted Answer

Mass spectrometer

Question 11

If an atom has 6 protons, 8 neutrons, and 6 electrons, what is its mass number ($$A$$)?

Accepted Answer

$$A = 14$$

Question 12

Which of the following elements has only one naturally occurring isotope?

Accepted Answer

$$^{19}F$

Question 13

A gallium sample has an average atomic mass of 69.723 u. If $$^{69}Ga $$has a mass of 68.926 u and $$^{71}Ga $$has a mass of 70.925 u, which isotope is more abundant?

Accepted Answer

$$^{69}Ga$$

Question 14

Which postulate of Dalton’s atomic theory has been modified based on modern evidence?

Accepted Answer

Atoms are indivisible and indestructible.

Question 15

Which of the following best explains why atomic masses on the periodic table are not whole numbers?

Accepted Answer

They are weighted averages of all naturally occurring isotopes.

Question 16

Which real-world technology relies on the photoelectric effect, a phenomenon explained by atomic structure?

Accepted Answer

Solar panels

Question 17

Which element is defined by having 43 protons in its nucleus?

Accepted Answer

Technetium

Question 18

Which of the following is a direct application of the law of constant composition?

Accepted Answer

A sample of sodium chloride always contains sodium and chlorine in a 1:1 ratio.

Question 19

Which of the following best describes the difference between a compound and a mixture?

Accepted Answer

A compound has elements combined in fixed ratios; a mixture does not.

Question 20

Which of the following is NOT a subatomic particle found in the nucleus?

Accepted Answer

Electron

Atomic Structure and Isotopes: Foundations of Modern Chemistry

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