WGU D425: INTRODUCTION TO CHEMISTRY
1, AND VERIFIED ANSWERS 100%
CORRECT GRADE A
49 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Apply quantum mechanical models to predict electronic structure and periodic properties
2 Perform multi-step stoichiometric and thermochemical calculations with precision
3 Analyze molecular geometry, bonding, and intermolecular forces to predict macroscopic properties
4 Evaluate acid-base equilibria and reaction kinetics using quantitative relationships
5 Integrate gas laws, solution chemistry, and thermodynamic principles in complex problem-solving
6 WGU D425
7 Introduction to chemistry 1
8 and Verified Answers 100% Correct Grade A
9 Foundations of Chemistry - Introduction to Chemistry 1
10 Applied Chemistry - Introduction to Chemistry 1
11 Advanced Chemistry - Introduction to Chemistry 1
12 Chemistry - Introduction to Chemistry 1 Review
ABSTRACT
This study document brings together 49 carefully worded exam questions drawn from WGU D425:
Introduction to chemistry 1, and Verified Answers 100% Correct Grade A, with the strongest
emphasis placed on Apply quantum mechanical models to predict electronic structure and periodic
properties, Perform multi-step stoichiometric and thermochemical calculations with precision,
Analyze molecular geometry, bonding and and intermolecular forces to predict macroscopic
properties. Every item follows the wording style and level of reasoning you meet in the real paper,
and each one is paired with a clear rationale so the correct choice is never a guess. Work through
the set at your own pace, mark the questions that slow you down, then come back to them until the
reasoning feels automatic. Learners who revise this way walk into the exam room recognising the
pattern behind the questions instead of meeting them for the first time. Keep going - steady, honest
practice is what turns a difficult paper into a comfortable pass.
Page 1
,Q1 APPLY QUANTUM MECHANICAL MODELS TO PREDICT ELECTRONIC STRUCTURE AND
PERIODIC PROPERTIES
An electron transitions from n=5 to n=2 in a hydrogen atom. Which statement
correctly describes the photon emitted and the spectral series?
A. The photon is in the Balmer series, and its energy equals the difference between the n=5 and
n=2 energy levels. CORRECT
B. The photon is in the Lyman series, and its energy equals the sum of the n=5 and n=2 energy
levels.
C. The photon is in the Paschen series, and its energy equals the ionization energy of hydrogen.
D. The photon is in the Brackett series, and its energy equals the Rydberg constant multiplied by
Planck's constant.
RATIONALE: Transitions ending at n=2 belong to the Balmer series (visible region). The emitted
photon's energy is exactly the energy difference between the initial and final levels, E = E5 E2.
Lyman series ends at n=1, Paschen at n=3, and Brackett at n=4, so B, C, and D are incorrect.
Q2 APPLY QUANTUM MECHANICAL MODELS TO PREDICT ELECTRONIC STRUCTURE AND
PERIODIC PROPERTIES
A 0.500 g sample of an unknown hydrocarbon is burned in excess oxygen,
producing 1.527 g CO and 0.625 g HO. What is the empirical formula of the
hydrocarbon?
A. CH CORRECT
B. CH
C. CH
D. CH
RATIONALE: Moles C = 1.527/44.01 = 0.0347; moles H = 2 × (0.625/18.02) = 0.0694. Ratio C:H
= 1:2, giving CH. The other formulas have different C:H ratios and would yield different product
masses.
Page 2
, Q3 APPLY QUANTUM MECHANICAL MODELS TO PREDICT ELECTRONIC STRUCTURE AND
PERIODIC PROPERTIES
Which of the following correctly ranks the elements K, Ca, Sc, and Ti by increasing
first ionization energy?
A. K < Ca < Sc < Ti CORRECT
B. Ti < Sc < Ca < K
C. K < Sc < Ca < Ti
D. Ca < K < Sc < Ti
RATIONALE: Across Period 4, effective nuclear charge increases while atomic radius decreases,
so first ionization energy generally increases from K to Ti. K has the lowest IE (easy to remove
4s¹ electron), and Ti has the highest among these. The other orders violate the periodic trend.
Q4 APPLY QUANTUM MECHANICAL MODELS TO PREDICT ELECTRONIC STRUCTURE AND
PERIODIC PROPERTIES
For the reaction N(g) + 3H(g) -> 2NH(g), H° = 92 kJ/mol. Which change will increase
the equilibrium yield of NH?
A. Increasing temperature and decreasing pressure
B. Decreasing temperature and increasing pressure CORRECT
C. Adding a catalyst and increasing volume
D. Removing N and increasing temperature
RATIONALE: The reaction is exothermic (H < 0) and reduces moles of gas (4 -> 2). By Le
Chatelier's principle, lowering temperature favors the exothermic forward direction, and
increasing pressure favors the side with fewer gas moles-both increase NH yield. Catalysts do
not shift equilibrium, and the other options oppose the favorable conditions.
Page 3
1, AND VERIFIED ANSWERS 100%
CORRECT GRADE A
49 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Apply quantum mechanical models to predict electronic structure and periodic properties
2 Perform multi-step stoichiometric and thermochemical calculations with precision
3 Analyze molecular geometry, bonding, and intermolecular forces to predict macroscopic properties
4 Evaluate acid-base equilibria and reaction kinetics using quantitative relationships
5 Integrate gas laws, solution chemistry, and thermodynamic principles in complex problem-solving
6 WGU D425
7 Introduction to chemistry 1
8 and Verified Answers 100% Correct Grade A
9 Foundations of Chemistry - Introduction to Chemistry 1
10 Applied Chemistry - Introduction to Chemistry 1
11 Advanced Chemistry - Introduction to Chemistry 1
12 Chemistry - Introduction to Chemistry 1 Review
ABSTRACT
This study document brings together 49 carefully worded exam questions drawn from WGU D425:
Introduction to chemistry 1, and Verified Answers 100% Correct Grade A, with the strongest
emphasis placed on Apply quantum mechanical models to predict electronic structure and periodic
properties, Perform multi-step stoichiometric and thermochemical calculations with precision,
Analyze molecular geometry, bonding and and intermolecular forces to predict macroscopic
properties. Every item follows the wording style and level of reasoning you meet in the real paper,
and each one is paired with a clear rationale so the correct choice is never a guess. Work through
the set at your own pace, mark the questions that slow you down, then come back to them until the
reasoning feels automatic. Learners who revise this way walk into the exam room recognising the
pattern behind the questions instead of meeting them for the first time. Keep going - steady, honest
practice is what turns a difficult paper into a comfortable pass.
Page 1
,Q1 APPLY QUANTUM MECHANICAL MODELS TO PREDICT ELECTRONIC STRUCTURE AND
PERIODIC PROPERTIES
An electron transitions from n=5 to n=2 in a hydrogen atom. Which statement
correctly describes the photon emitted and the spectral series?
A. The photon is in the Balmer series, and its energy equals the difference between the n=5 and
n=2 energy levels. CORRECT
B. The photon is in the Lyman series, and its energy equals the sum of the n=5 and n=2 energy
levels.
C. The photon is in the Paschen series, and its energy equals the ionization energy of hydrogen.
D. The photon is in the Brackett series, and its energy equals the Rydberg constant multiplied by
Planck's constant.
RATIONALE: Transitions ending at n=2 belong to the Balmer series (visible region). The emitted
photon's energy is exactly the energy difference between the initial and final levels, E = E5 E2.
Lyman series ends at n=1, Paschen at n=3, and Brackett at n=4, so B, C, and D are incorrect.
Q2 APPLY QUANTUM MECHANICAL MODELS TO PREDICT ELECTRONIC STRUCTURE AND
PERIODIC PROPERTIES
A 0.500 g sample of an unknown hydrocarbon is burned in excess oxygen,
producing 1.527 g CO and 0.625 g HO. What is the empirical formula of the
hydrocarbon?
A. CH CORRECT
B. CH
C. CH
D. CH
RATIONALE: Moles C = 1.527/44.01 = 0.0347; moles H = 2 × (0.625/18.02) = 0.0694. Ratio C:H
= 1:2, giving CH. The other formulas have different C:H ratios and would yield different product
masses.
Page 2
, Q3 APPLY QUANTUM MECHANICAL MODELS TO PREDICT ELECTRONIC STRUCTURE AND
PERIODIC PROPERTIES
Which of the following correctly ranks the elements K, Ca, Sc, and Ti by increasing
first ionization energy?
A. K < Ca < Sc < Ti CORRECT
B. Ti < Sc < Ca < K
C. K < Sc < Ca < Ti
D. Ca < K < Sc < Ti
RATIONALE: Across Period 4, effective nuclear charge increases while atomic radius decreases,
so first ionization energy generally increases from K to Ti. K has the lowest IE (easy to remove
4s¹ electron), and Ti has the highest among these. The other orders violate the periodic trend.
Q4 APPLY QUANTUM MECHANICAL MODELS TO PREDICT ELECTRONIC STRUCTURE AND
PERIODIC PROPERTIES
For the reaction N(g) + 3H(g) -> 2NH(g), H° = 92 kJ/mol. Which change will increase
the equilibrium yield of NH?
A. Increasing temperature and decreasing pressure
B. Decreasing temperature and increasing pressure CORRECT
C. Adding a catalyst and increasing volume
D. Removing N and increasing temperature
RATIONALE: The reaction is exothermic (H < 0) and reduces moles of gas (4 -> 2). By Le
Chatelier's principle, lowering temperature favors the exothermic forward direction, and
increasing pressure favors the side with fewer gas moles-both increase NH yield. Catalysts do
not shift equilibrium, and the other options oppose the favorable conditions.
Page 3
