, CHEM 121 FINAL - Original Practice Study Guide
CHEM 121 Final Module Exam Portage General
Chemistry w/Lab 100% Correct
1. Which value has four significant figures?
A) 0.004560
B) 0.0045
C) 4500 without a decimal point
D) 0.040
Correct Answer: 0.004560
Rationale: Leading zeros are not significant, but trailing zeros after a decimal are significant; 0.004560 has four
significant figures.
2. A CHEM 121 student is applying this concept on a cumulative final-review problem. convert 25.0 °C to
kelvin.
A) 325.0 K
B) 248.15 K
C) 273.15 K
D) 298.15 K
Correct Answer: 298.15 K
Rationale: Kelvin temperature equals degrees Celsius plus 273.15. Solving cumulative chemistry problems requires
selecting the relevant model or equation, tracking units and signs, and checking whether the result is chemically
reasonable.
3. A CHEM 121 student is applying this concept on a cumulative final-review problem. a sample has a
mass of 45.0 g and a volume of 15.0 mL. What is its density?
A) 3.00 g/mL
B) 0.333 g/mL
C) 30.0 g/mL
D) 60.0 g/mL
Correct Answer: 3.00 g/mL
Rationale: Density equals mass divided by volume: 45.0/15.0 = 3.00 g/mL. Solving cumulative chemistry problems
requires selecting the relevant model or equation, tracking units and signs, and checking whether the result is
chemically reasonable.
4. A CHEM 121 student is applying this concept on a cumulative final-review problem. which is a chemical
change?
A) Water boiling
B) Ice melting
C) Iron rusting
D) Glass breaking
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, CHEM 121 FINAL - Original Practice Study Guide
Correct Answer: Iron rusting
Rationale: Rusting produces new substances, whereas melting, boiling, and breaking are physical changes. Solving
cumulative chemistry problems requires selecting the relevant model or equation, tracking units and signs, and
checking whether the result is chemically reasonable.
5. Which is a homogeneous mixture?
A) Granite
B) Saltwater
C) Oil and water
D) Sand in water
Correct Answer: Saltwater
Rationale: A homogeneous mixture has uniform composition throughout.
6. A CHEM 121 student is applying this concept on a cumulative final-review problem. which particle
determines the atomic number?
A) Neutron
B) Proton
C) Electron only
D) Photon
Correct Answer: Proton
Rationale: Atomic number equals the number of protons in the nucleus. Solving cumulative chemistry problems
requires selecting the relevant model or equation, tracking units and signs, and checking whether the result is
chemically reasonable.
7. A CHEM 121 student is applying this concept on a cumulative final-review problem. an atom has 17
protons and 18 electrons. What is its charge?
A) 0
B) +1
C) -1
D) -2
Correct Answer: -1
Rationale: One extra electron relative to protons gives a net -1 charge. Solving cumulative chemistry problems
requires selecting the relevant model or equation, tracking units and signs, and checking whether the result is
chemically reasonable.
8. A CHEM 121 student is applying this concept on a cumulative final-review problem. which pair
represents isotopes of the same element?
A) Atoms with different protons and same neutrons
B) Atoms with the same protons but different neutrons
C) Two ions with different proton numbers
D) Two compounds with same mass
Page 3
CHEM 121 Final Module Exam Portage General
Chemistry w/Lab 100% Correct
1. Which value has four significant figures?
A) 0.004560
B) 0.0045
C) 4500 without a decimal point
D) 0.040
Correct Answer: 0.004560
Rationale: Leading zeros are not significant, but trailing zeros after a decimal are significant; 0.004560 has four
significant figures.
2. A CHEM 121 student is applying this concept on a cumulative final-review problem. convert 25.0 °C to
kelvin.
A) 325.0 K
B) 248.15 K
C) 273.15 K
D) 298.15 K
Correct Answer: 298.15 K
Rationale: Kelvin temperature equals degrees Celsius plus 273.15. Solving cumulative chemistry problems requires
selecting the relevant model or equation, tracking units and signs, and checking whether the result is chemically
reasonable.
3. A CHEM 121 student is applying this concept on a cumulative final-review problem. a sample has a
mass of 45.0 g and a volume of 15.0 mL. What is its density?
A) 3.00 g/mL
B) 0.333 g/mL
C) 30.0 g/mL
D) 60.0 g/mL
Correct Answer: 3.00 g/mL
Rationale: Density equals mass divided by volume: 45.0/15.0 = 3.00 g/mL. Solving cumulative chemistry problems
requires selecting the relevant model or equation, tracking units and signs, and checking whether the result is
chemically reasonable.
4. A CHEM 121 student is applying this concept on a cumulative final-review problem. which is a chemical
change?
A) Water boiling
B) Ice melting
C) Iron rusting
D) Glass breaking
Page 2
, CHEM 121 FINAL - Original Practice Study Guide
Correct Answer: Iron rusting
Rationale: Rusting produces new substances, whereas melting, boiling, and breaking are physical changes. Solving
cumulative chemistry problems requires selecting the relevant model or equation, tracking units and signs, and
checking whether the result is chemically reasonable.
5. Which is a homogeneous mixture?
A) Granite
B) Saltwater
C) Oil and water
D) Sand in water
Correct Answer: Saltwater
Rationale: A homogeneous mixture has uniform composition throughout.
6. A CHEM 121 student is applying this concept on a cumulative final-review problem. which particle
determines the atomic number?
A) Neutron
B) Proton
C) Electron only
D) Photon
Correct Answer: Proton
Rationale: Atomic number equals the number of protons in the nucleus. Solving cumulative chemistry problems
requires selecting the relevant model or equation, tracking units and signs, and checking whether the result is
chemically reasonable.
7. A CHEM 121 student is applying this concept on a cumulative final-review problem. an atom has 17
protons and 18 electrons. What is its charge?
A) 0
B) +1
C) -1
D) -2
Correct Answer: -1
Rationale: One extra electron relative to protons gives a net -1 charge. Solving cumulative chemistry problems
requires selecting the relevant model or equation, tracking units and signs, and checking whether the result is
chemically reasonable.
8. A CHEM 121 student is applying this concept on a cumulative final-review problem. which pair
represents isotopes of the same element?
A) Atoms with different protons and same neutrons
B) Atoms with the same protons but different neutrons
C) Two ions with different proton numbers
D) Two compounds with same mass
Page 3
