Chapter 3—Atoms and Moles



Chapter 3—Atoms and Moles

MULTIPLE CHOICE

1. The law of conservation of mass follows from the concept that

|a. |atoms are indivisible. |

|b. |atoms of different elements have different properties. |

|c. |matter is composed of atoms. |

|d. |atoms can be destroyed in chemical reactions. |

ANS: A PTS: 1 DIF: I OBJ: 3.1.1

2. The composition of the two oxides of lead, PbO and PbO2, are explained by the

|a. |periodic law. |c. |atomic law. |

|b. |law of multiple proportions. |d. |law of conservation of mass. |

ANS: B PTS: 1 DIF: II OBJ: 3.1.1

3. Who first proposed an atomic theory based on scientific knowledge?

|a. |John Dalton |c. |Robert Brown |

|b. |Jons Berzelius |d. |Dmitri Mendeleev |

ANS: A PTS: 1 DIF: I OBJ: 3.1.2

4. According to Dalton’s atomic theory, atoms

|a. |are destroyed in chemical reactions. |

|b. |can be divided. |

|c. |of each element are identical in size, mass, and other properties. |

|d. |of different elements cannot combine. |

ANS: C PTS: 1 DIF: I OBJ: 3.1.2

5. Which of the following is NOT part of Dalton’s atomic theory?

|a. |Atoms cannot be divided, created, or destroyed. |

|b. |The number of protons in an atom is its atomic number. |

|c. |In chemical reactions, atoms are combined, separated, or rearranged. |

|d. |All matter is composed of extremely small particles called atoms. |

ANS: B PTS: 1 DIF: I OBJ: 3.1.2

6. The law of definite proportions

|a. |contradicted Dalton’s atomic theory. |

|b. |was explained by Dalton’s atomic theory. |

|c. |replaced the law of conservation of mass. |

|d. |assumes that atoms of all elements are identical. |

ANS: B PTS: 1 DIF: I OBJ: 3.1.2

15. The mass of a neutron is

|a. |about the same as that of a proton. |c. |double that of a proton. |

|b. |about the same as that of an electron. |d. |double that of an electron. |

ANS: A PTS: 1 DIF: I OBJ: 3.2.1

16. The nucleus of most atoms is composed of

|a. |tightly packed protons. |

|b. |tightly packed neutrons. |

|c. |tightly packed protons and neutrons. |

|d. |loosely connected protons and electrons. |

ANS: C PTS: 1 DIF: I OBJ: 3.2.1

17. Protons and neutrons strongly attract when they

|a. |are moving fast. |c. |are at high energies. |

|b. |are very close together. |d. |have opposite charges. |

ANS: B PTS: 1 DIF: I OBJ: 3.2.1

18. An aluminum isotope consists of 13 protons, 13 electrons, and 14 neutrons. Its mass number is

|a. |13. |c. |27. |

|b. |14. |d. |40. |

ANS: C PTS: 1 DIF: II OBJ: 3.2.2

19. Isotopes are atoms of the same element that have different

|a. |principal chemical properties. |c. |numbers of protons. |

|b. |masses. |d. |numbers of electrons. |

ANS: B PTS: 1 DIF: I OBJ: 3.2.3

20. Atoms of the same element that have different masses are called

|a. |moles. |c. |nuclides. |

|b. |isotopes. |d. |neutrons. |

ANS: B PTS: 1 DIF: I OBJ: 3.2.3

21. Isotopes of an element contain different numbers of

|a. |electrons. |c. |neutrons. |

|b. |protons. |d. |nuclides. |

ANS: C PTS: 1 DIF: I OBJ: 3.2.3

COMPLETION

1. The statement that a chemical compound always contains the same elements in exactly the same proportions is called the law of _________________________.

ANS: definite proportions

PTS: 1 DIF: I OBJ: 3.1.1

2. The statement that mass cannot be created or destroyed in ordinary chemical and physical changes is called the law of _________________________.

ANS: conservation of mass

PTS: 1 DIF: I OBJ: 3.1.1

3. The statement that when two elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other element is in the ratio of small whole numbers is known as the law of _________________________.

ANS: multiple proportions

PTS: 1 DIF: I OBJ: 3.1.1

4. A subatomic particle that has a negative electric change is a(n) ____________________.

ANS: electron

PTS: 1 DIF: I OBJ: 3.2.1

5. An atom’s central region, which is made up of protons and neutrons, is the ____________________.

ANS: nucleus

PTS: 1 DIF: I OBJ: 3.2.1

6. A subatomic particle that has a positive charge and that is found in the nucleus of an atom is a(n) ____________________.

ANS: proton

PTS: 1 DIF: I OBJ: 3.2.1

7. A subatomic particle that has no charge and is found in the nucleus is a(n) ____________________.

ANS: neutron

PTS: 1 DIF: I OBJ: 3.2.1

8. The number of protons in the nucleus of an atom is called the ____________________.

ANS: atomic number

PTS: 1 DIF: I OBJ: 3.2.2

9. The sum of the numbers of protons and neutrons of the nucleus of an atom is called the ____________________.

ANS: mass number

PTS: 1 DIF: I OBJ: 3.2.2

10. An atom that has the same number of protons as other atoms of the same element but has a different number of neutrons is called a(n) ____________________.

ANS: isotope

PTS: 1 DIF: I OBJ: 3.2.3

11. Another method of writing the nickel isotope, [pic], is ____________________.

ANS: nickel-58

PTS: 1 DIF: I OBJ: 3.2.3

12. A region in an atom where there is a high probability of finding electrons is called a(n) ____________________.

ANS: orbital

PTS: 1 DIF: I OBJ: 3.3.1

13. Orbitals are sometimes called electron ____________________ because they do not have hard boundaries.

ANS: clouds

PTS: 1 DIF: I OBJ: 3.3.1

14. All of the frequencies or wavelengths of electromagnetic radiation make up the electromagnetic ____________________.

ANS: spectrum

PTS: 1 DIF: I OBJ: 3.3.2

15. The wavelength of electromagnetic radiation is inversely proportional to its ____________________.

ANS: frequency

PTS: 1 DIF: II OBJ: 3.3.2

16. Light can be thought of as a stream of particles, the ____________________ of which is determined by the light’s frequency.

ANS: energy

PTS: 1 DIF: III OBJ: 3.3.2

17. A state in which an atom has more energy than it does in its ground state is called a(n) ____________________.

ANS: excited state

PTS: 1 DIF: I OBJ: 3.3.2

18. A number that specifies a property of an orbital is called a(n) ____________________.

ANS: quantum number

PTS: 1 DIF: I OBJ: 3.3.3

19. The statement that two particles of a certain class cannot be in the exact same energy state is known as the ____________________ principle.

ANS: Pauli exclusion

PTS: 1 DIF: I OBJ: 3.3.4

20. The _________________________ of an atom is the arrangement of its electrons.

ANS: electron configuration

PTS: 1 DIF: I OBJ: 3.3.4

21. The statement that the structure of each successive element is obtained by adding one proton to the nucleus of the atom and one electron to the lowest-energy orbital that is available is known as the ____________________ principle.

ANS: aufbau

PTS: 1 DIF: I OBJ: 3.3.4

22. The statement that for an atom in the ground state, the number of unpaired electrons is the maximum possible and these unpaired electrons have the same spin is known as ____________________ rule.

ANS: Hund’s

PTS: 1 DIF: I OBJ: 3.3.4

23. The mass of an atom expressed in atomic mass units is the ____________________.

ANS: atomic mass

PTS: 1 DIF: I OBJ: 3.4.1

24. The SI base unit used to measure the amount of a substance whose number of particles is the same as the number of particles in 12 g of carbon-12 is called the ____________________.

ANS: mole

PTS: 1 DIF: I OBJ: 3.4.2

25. Avogadro’s number has a value (to three significant figures) of ____________________.

ANS: 6.02 × 1023

PTS: 1 DIF: I OBJ: 3.4.2

26. The mass in grams of 1 mol of a substance is the substance’s ____________________.

ANS: molar mass

PTS: 1 DIF: I OBJ: 3.4.2

SHORT ANSWER

1. What is the atomic number of the atom [pic] ?

ANS:

15

PTS: 1 DIF: I OBJ: 3.2.2

2. What is the mass number of the atom [pic] ?

ANS:

86

PTS: 1 DIF: I OBJ: 3.2.2

3. How many electrons are in a neutral atom of [pic] ?

ANS:

56

PTS: 1 DIF: I OBJ: 3.2.2

4. How many protons are in an atom of [pic] ?

ANS:

40

PTS: 1 DIF: I OBJ: 3.2.2

5. How many neutrons are in an atom of [pic] ?

ANS:

82

PTS: 1 DIF: I OBJ: 3.2.2

6. What is the molar mass of tin, which has an atomic mass of 118.7 amu?

ANS:

118.7 g/mol

PTS: 1 DIF: I OBJ: 3.2.2

PROBLEM

1. What is the mass of 2.5 moles of carbon?

ANS:

[pic]

PTS: 1 DIF: II OBJ: 3.4.3

2. How many moles of copper are present in 180.0 g Cu?

ANS:

[pic]

PTS: 1 DIF: II OBJ: 3.4.3

3. The mass of 1 mol of gold atoms is 196.97 g. Find the mass of 1 atom of gold.

ANS:

[pic]

PTS: 1 DIF: III OBJ: 3.4.3

4. How many atoms are in 0.12 mol of cadmium?

ANS:

[pic]

PTS: 1 DIF: II OBJ: 3.4.3

ESSAY

1. Describe atomic mass.

ANS:

Atomic mass is the sum of the masses of the total number of protons and neutrons in the atom.

PTS: 1 DIF: I OBJ: 3.2.2

2. Describe the atomic mass unit.

ANS:

The atomic mass unit is the average of the mass of the protons and neutrons in the carbon-12 isotope.

PTS: 1 DIF: I OBJ: 3.4.1

3. How are the atomic mass unit and the atomic mass related?

ANS:

The atomic mass is the atomic mass unit multiplied by the number of protons and neutrons in the atom.

PTS: 1 DIF: I OBJ: 3.4.1

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