Q: Given the following isotopes of neon: $^{20}$Ne (90.48%), $^{21}$Ne (0.27%), and $^{22}$Ne (9.25%), calculate the average atomic mass of neon. (Atomic masses: $^{20}$Ne = 19.992 amu, $^{21}$Ne = 20.994 amu, $^{22}$Ne = 21.991 amu)

$(19.992 \times 0.9048) + (20.994 \times 0.0027) + (21.991 \times 0.0925) = 20.179$ amu

Question 1

Which of the following best describes the Law of Conservation of Mass?

Accepted Answer

The total mass of the reactants in a chemical reaction is equal to the total mass of the products.

Question 2

A sample of calcium oxide (CaO) is formed by decomposing 10.0 g of CaCO$_3$ to produce 5.60 g of CaO and 4.40 g of CO$_2$. Which law does this experiment best illustrate?

Accepted Answer

Law of Conservation of Mass

Question 3

Which of the following statements is consistent with the Law of Definite Proportions?

Accepted Answer

All samples of a given compound have the same proportions of their constituent elements.

Question 4

Carbon forms two oxides: CO and CO$_2$. If 2.67 g of O reacts with 1.00 g of C to form CO, and 5.34 g of O reacts with 1.00 g of C to form CO$_2$, what is the ratio of the masses of oxygen that combine with a fixed mass of carbon in these two compounds?

Accepted Answer

$\frac{5.34}{2.67} = 2.00$

Question 5

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

Accepted Answer

Atoms are created and destroyed in chemical reactions.

Question 6

Which experiment provided the first direct evidence for the existence of the electron?

Accepted Answer

J.J. Thomson's cathode ray tube experiment

Question 7

In Millikan's oil drop experiment, what fundamental property of the electron was determined?

Accepted Answer

The charge of the electron

Question 8

Which observation from Rutherford's gold foil experiment led to the nuclear model of the atom?

Accepted Answer

Most alpha particles passed through the foil, but a few were deflected at large angles.

Question 9

Which of the following statements about subatomic particles is correct?

Accepted Answer

Protons and neutrons have approximately the same mass.

Question 10

A neutral atom of an element has 17 protons, 18 neutrons, and 17 electrons. What is the mass number and atomic number of this atom?

Accepted Answer

Mass number = 35, Atomic number = 17

Question 11

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 12

Given the following isotopes of neon: $^{20}$Ne (90.48%), $^{21}$Ne (0.27%), and $^{22}$Ne (9.25%), calculate the average atomic mass of neon. (Atomic masses: $^{20}$Ne = 19.992 amu, $^{21}$Ne = 20.994 amu, $^{22}$Ne = 21.991 amu)

Accepted Answer

$(19.992 	imes 0.9048) + (20.994 	imes 0.0027) + (21.991 	imes 0.0925) = 20.179$ amu

Question 13

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

Accepted Answer

Elements in the same vertical column have similar chemical properties.

Question 14

Which of the following is a property of metals as described in the periodic table?

Accepted Answer

They are shiny solids that conduct heat and electricity.

Question 15

Which of the following best explains why the charge-to-mass ratio ($e/m$) of the electron was important in the discovery of subatomic particles?

Accepted Answer

It allowed scientists to determine that electrons are much lighter than atoms.

Question 16

Which of the following is a correct statement about the nuclear theory of the atom?

Accepted Answer

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

Question 17

A sample contains 80.0 g of phosphorus and 124.0 g of chlorine, forming two different compounds. In the first compound, 124.0 g of chlorine combines with 56.0 g of phosphorus. In the second, 124.0 g of chlorine combines with 80.0 g of phosphorus. What is the ratio of phosphorus masses that combine with a fixed mass of chlorine, and does this support the law of multiple proportions?

Accepted Answer

$\frac{80.0}{56.0} = 1.43$, which is a small whole number ratio, supporting the law of multiple proportions.

Question 18

Which of the following is NOT a property of electric charge?

Accepted Answer

Like charges attract each other.

Question 19

Which of the following best describes the difference between atomic number and mass number?

Accepted Answer

Atomic number is the number of protons; mass number is the sum of protons and neutrons.

Atoms and Elements: Fundamental Concepts in General Chemistry

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