Q: Calculate the number of atoms in 14.955 g of carbon. (Atomic mass of C = 12.01 g/mol, $$N_A = 6.02 \times 10$$^{23}$$ atoms/mol)

$$7.50 \times 10$$^{23}$$ atoms

Q: A sample contains 3.7 g of silver (Ag). How many atoms are present? (Atomic mass of Ag = 107.87 g/mol, $$N_A = 6.02 \times 10$$^{23}$$ atoms/mol)

$$2.06 \times 10$$^{22}$$ atoms

Question 1

Which statement best describes the Law of Conservation of Mass?

Accepted Answer

Matter is neither created nor destroyed during a chemical or physical change.

Question 2

A compound is analyzed and found to always contain 39.34% sodium and 60.66% chlorine by mass, regardless of the sample size. Which law does this observation illustrate?

Accepted Answer

Law of Definite Proportions

Question 3

Which of the following is a correct application of the Law of Multiple Proportions?

Accepted Answer

Two elements can combine in different ratios to form different compounds.

Question 4

A chemist decomposes several samples of carbon monoxide (CO) and finds the mass ratio of oxygen to carbon is always 1.33. What does this result support?

Accepted Answer

Law of Definite Proportions

Question 5

Which statement is NOT consistent with Dalton's Atomic Theory?

Accepted Answer

Atoms can be created or destroyed in chemical reactions.

Question 6

In the Millikan oil-drop experiment, what physical quantity was directly measured?

Accepted Answer

The charge of a single electron

Question 7

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 8

A neutral atom of sodium has 11 protons and 11 electrons. What is the charge of a sodium ion (Na⁺)?

Accepted Answer

+1

Question 9

Which statement about subatomic particles is TRUE?

Accepted Answer

Protons and neutrons have nearly the same mass.

Question 10

A mass spectrum shows two peaks for gallium at 68.9256 amu and 70.9247 amu. If the relative abundances are 60.11% and 39.89%, respectively, which isotope is more abundant?

Accepted Answer

Ga-69

Question 11

Which of the following diagrams represents a homogeneous mixture?

Accepted Answer

A diagram with two types of particles evenly distributed throughout

Question 12

Which of the following is a compound?

Accepted Answer

Carbon monoxide (CO)

Question 13

Calculate the number of atoms in 14.955 g of carbon. (Atomic mass of C = 12.01 g/mol, $$N_A = 6.02 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$7.50 	imes 10$$^{23}$$ atoms

Question 14

Which of the following is the correct isotopic symbol for the silver isotope with 60 neutrons? (Atomic number of Ag = 47)

Accepted Answer

$$^{107}_{47}Ag$$

Question 15

A sample contains 3.7 g of silver (Ag). How many atoms are present? (Atomic mass of Ag = 107.87 g/mol, $$N_A = 6.02 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$2.06 	imes 10$$^{22}$$ atoms

Question 16

Which of the following best describes a cation?

Accepted Answer

An atom that has lost electrons and has a positive charge

Question 17

Which statement about mass spectrometry is correct?

Accepted Answer

It determines the mass-to-charge ratio ($$m/z) of $$ions.

Question 18

A hydrogen-filled balloon is ignited and 1.50 g of hydrogen reacts with 12.0 g of oxygen. How many grams of water vapor form? (Law of Conservation of Mass)

Accepted Answer

13.5 g

Question 19

Which of the following is a heterogeneous mixture?

Accepted Answer

Sand and iron filings

Question 20

Which statement is true regarding the atomic mass of an element?

Accepted Answer

It is the weighted average of all naturally occurring isotopes.

Foundations of Atomic Theory, Laws of Chemical Combination, Isotopes, Ions, and the Mole Concept

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