WGU D425 Intro to Chemistry Objective
Assessment Actual Exam 2025/2026 |
Questions with Verified Answers | 100%
Correct | Pass Guaranteed
Q001: How many protons, neutrons, and electrons are in an atom of
sulfur-34?
Options:
• A. 16 p, 16 n, 16 e
• B. 16 p, 18 n, 16 e
• C. 16 p, 18 n, 16 e
• D. 18 p, 16 n, 18 e
ANSWER: C
Detailed Answer: Sulfur has atomic number 16, so it always has 16
protons and 16 electrons in the neutral atom. The mass number is 34, so
neutrons = 34 − 16 = 18.
Q002: Which ionic compound is correctly named?
Options:
• A. MgCl₂ magnesium dichloride
• B. Al₂O₃ dialuminum trioxide
• C. Na₂O sodium oxide
• D. Ca₃N₂ calcium nitrate
ANSWER: C
,Detailed Answer: Na₂O contains Na⁺ and O²⁻ ions. The crisscross rule
gives a 2:1 ratio, and the name is simply sodium oxide because sodium
only forms +1 ions.
Q003: What is the molar mass of Ca(NO₃)₂?
Options:
• A. 102.1 g/mol
• B. 132.1 g/mol
• C. 164.1 g/mol
• D. 202.1 g/mol
ANSWER: C
Detailed Answer: Ca = 40.08, N = 14.01 × 2 = 28.02, O = 16.00 × 6 =
96.00.
Sum = 40.08 + 28.02 + 96.00 = 164.1 g/mol.
Q004: How many moles of CO₂ are in 88.0 g of CO₂?
Options:
• A. 1.00 mol
• B. 2.00 mol
• C. 2.00 mol
• D. 4.00 mol
ANSWER: C
Detailed Answer: Molar mass of CO₂ = 44.01 g/mol.
88.0 g ÷ 44.01 g/mol ≈ 2.00 mol.
,Q005: What is the oxidation state of Cl in ClO₄⁻?
Options:
• A. +1
• B. +5
• C. +7
• D. −1
ANSWER: C
Detailed Answer (Q005): Oxygen is −2 (×4 = −8), overall charge = −1.
Let chlorine = x:
x + (−8) = −1
x = +7
Q006: Which bond is most polar?
Options:
• A. H–H
• B. O–H
• C. N–H
• D. C–H
ANSWER: B
Detailed Answer: Electronegativity difference: O (3.44) − H (2.20) =
1.24, the largest listed, so O–H is the most polar.
Q007: How many valence electrons does phosphorus have?
, Options:
• A. 3
• B. 5
• C. 5
• D. 15
ANSWER: C
Detailed Answer: Phosphorus is in Group 15; therefore, it has 5
valence electrons.
Q008: What is the electron configuration of Al³⁺?
Options:
• A. 1s² 2s² 2p⁶ 3s² 3p¹
• B. 1s² 2s² 2p⁶ 3s²
• C. 1s² 2s² 2p⁶
• D. 1s² 2s² 2p⁶ 3s² 3p⁶
ANSWER: C
Detailed Answer: Neutral aluminum (Al) has the electron configuration
1s² 2s² 2p⁶ 3s² 3p¹. Forming Al³⁺ removes the three outermost electrons
(3p¹ and 3s²), leaving 1s² 2s² 2p⁶, which is the same electron
configuration as neon.
Q009: Which of the following is an example of a physical change?
Options:
Assessment Actual Exam 2025/2026 |
Questions with Verified Answers | 100%
Correct | Pass Guaranteed
Q001: How many protons, neutrons, and electrons are in an atom of
sulfur-34?
Options:
• A. 16 p, 16 n, 16 e
• B. 16 p, 18 n, 16 e
• C. 16 p, 18 n, 16 e
• D. 18 p, 16 n, 18 e
ANSWER: C
Detailed Answer: Sulfur has atomic number 16, so it always has 16
protons and 16 electrons in the neutral atom. The mass number is 34, so
neutrons = 34 − 16 = 18.
Q002: Which ionic compound is correctly named?
Options:
• A. MgCl₂ magnesium dichloride
• B. Al₂O₃ dialuminum trioxide
• C. Na₂O sodium oxide
• D. Ca₃N₂ calcium nitrate
ANSWER: C
,Detailed Answer: Na₂O contains Na⁺ and O²⁻ ions. The crisscross rule
gives a 2:1 ratio, and the name is simply sodium oxide because sodium
only forms +1 ions.
Q003: What is the molar mass of Ca(NO₃)₂?
Options:
• A. 102.1 g/mol
• B. 132.1 g/mol
• C. 164.1 g/mol
• D. 202.1 g/mol
ANSWER: C
Detailed Answer: Ca = 40.08, N = 14.01 × 2 = 28.02, O = 16.00 × 6 =
96.00.
Sum = 40.08 + 28.02 + 96.00 = 164.1 g/mol.
Q004: How many moles of CO₂ are in 88.0 g of CO₂?
Options:
• A. 1.00 mol
• B. 2.00 mol
• C. 2.00 mol
• D. 4.00 mol
ANSWER: C
Detailed Answer: Molar mass of CO₂ = 44.01 g/mol.
88.0 g ÷ 44.01 g/mol ≈ 2.00 mol.
,Q005: What is the oxidation state of Cl in ClO₄⁻?
Options:
• A. +1
• B. +5
• C. +7
• D. −1
ANSWER: C
Detailed Answer (Q005): Oxygen is −2 (×4 = −8), overall charge = −1.
Let chlorine = x:
x + (−8) = −1
x = +7
Q006: Which bond is most polar?
Options:
• A. H–H
• B. O–H
• C. N–H
• D. C–H
ANSWER: B
Detailed Answer: Electronegativity difference: O (3.44) − H (2.20) =
1.24, the largest listed, so O–H is the most polar.
Q007: How many valence electrons does phosphorus have?
, Options:
• A. 3
• B. 5
• C. 5
• D. 15
ANSWER: C
Detailed Answer: Phosphorus is in Group 15; therefore, it has 5
valence electrons.
Q008: What is the electron configuration of Al³⁺?
Options:
• A. 1s² 2s² 2p⁶ 3s² 3p¹
• B. 1s² 2s² 2p⁶ 3s²
• C. 1s² 2s² 2p⁶
• D. 1s² 2s² 2p⁶ 3s² 3p⁶
ANSWER: C
Detailed Answer: Neutral aluminum (Al) has the electron configuration
1s² 2s² 2p⁶ 3s² 3p¹. Forming Al³⁺ removes the three outermost electrons
(3p¹ and 3s²), leaving 1s² 2s² 2p⁶, which is the same electron
configuration as neon.
Q009: Which of the following is an example of a physical change?
Options:
