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Key Facts: PAU Chemistry (Aragón) Exam

90 min

Exam Duration

UNIZAR PAU Commission

0–10

Grading Scale

Gobierno de Aragón

4.0 / 10

Min. Access Phase Mark

PAU Regulations

EUR 75.00

Ordinary Registration Fee

UNIZAR PAU inscription page 2026

The Aragón PAU Chemistry exam (Química) is administered by the PAU Organising Commission of Aragón / UNIZAR for 2nd Bachillerato students entering university. Lasting 90 minutes and graded on a 0–10 scale (minimum 4.0 required in the Access Phase), it tests mastery of physical, analytical, inorganic, and organic chemistry. Questions here serve as an English MCQ study adaptation for the Aragón PAU 2026 exam.

Sample PAU Chemistry (Aragón) Practice Questions

Try these sample questions to review concepts for the PAU Chemistry (Aragón) exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which set of quantum numbers (n, l, m_l, m_s) is allowed for an electron occupying a 3p orbital?

A.n = 3, l = 0, m_l = 1, m_s = +1/2

B.n = 2, l = 1, m_l = -1, m_s = +1/2

C.n = 3, l = 1, m_l = -1, m_s = +1/2

D.n = 3, l = 2, m_l = 0, m_s = -1/2

Explanation: For a 3p orbital, the principal quantum number is n = 3 and the azimuthal quantum number is l = 1. The magnetic quantum number m_l can take integer values from -l to +l (-1, 0, +1), and the spin quantum number m_s must be +1/2 or -1/2. The set (n = 3, l = 1, m_l = -1, m_s = +1/2) satisfies all these quantum mechanical rules.

2What is the ground-state electron configuration of the Fe²⁺ ion (atomic number Z = 26)?

A.[Ar] 3d⁶

B.[Ar] 4s² 3d⁴

C.[Ar] 4s¹ 3d⁵

D.[Ar] 3d⁵ 4s¹

Explanation: Neutral iron (Z = 26) has the ground-state electron configuration [Ar] 4s² 3d⁶. When transition metal atoms lose electrons to form cations, the outer 4s electrons are removed before 3d electrons. Thus, Fe²⁺ loses its two 4s electrons, resulting in [Ar] 3d⁶.

3Which of the following ground-state neutral atoms has the highest first ionization energy?

A.Fluorine (F)

B.Neon (Ne)

C.Chlorine (Cl)

D.Oxygen (O)

Explanation: First ionization energy generally increases across a period from left to right and decreases down a group. Neon (Ne) is a noble gas in Period 2 with a complete octet valence shell (2s² 2p⁶), giving it an exceptionally high effective nuclear charge and high ionization energy compared to F, Cl, and O.

4According to Pauling's scale, which element is the most electronegative?

A.Fluorine (F)

B.Oxygen (O)

C.Chlorine (Cl)

D.Helium (He)

Explanation: Fluorine has the highest electronegativity value on the Pauling scale (3.98), reflecting its strong tendency to attract shared electron pairs in covalent bonds due to its small radius and high effective nuclear charge.

5Which principle states that no two electrons in an atom can have the exact same four quantum numbers?

A.Aufbau Principle

B.Pauli Exclusion Principle

C.Heisenberg Uncertainty Principle

D.Hund's Rule of Maximum Multiplicity

Explanation: The Pauli Exclusion Principle dictates that no two electrons in a single atom can possess an identical set of four quantum numbers (n, l, m_l, m_s). Consequently, an atomic orbital can hold at most two electrons with opposite spins (+1/2 and -1/2).

6How many unpaired electrons are present in a ground-state neutral Nitrogen atom (Z = 7)?

A.2

B.3

C.0

D.1

Explanation: Nitrogen (Z = 7) has the ground-state electron configuration 1s² 2s² 2p³. According to Hund's rule, the three electrons in the 2p subshell occupy three separate degenerate orbitals (2px, 2py, 2pz) with parallel spins, giving 3 unpaired electrons.

7Which of the following species is isoelectronic with the Argon atom (Z = 18)?

A.S²⁻

B.Na⁺

C.F⁻

D.Mg²⁺

Explanation: Argon has 18 electrons (1s² 2s² 2p⁶ 3s² 3p⁶). Neutral Sulfur (Z = 16) gains 2 electrons to form S²⁻, giving it 16 + 2 = 18 electrons. Thus, S²⁻ is isoelectronic with Ar.

8Which list correctly orders the ionic radii of the isoelectronic species N³⁻, O²⁻, F⁻, and Na⁺ from largest to smallest?

A.F⁻ > O²⁻ > N³⁻ > Na⁺

B.N³⁻ > O²⁻ > F⁻ > Na⁺

C.N³⁻ > F⁻ > O²⁻ > Na⁺

D.Na⁺ > F⁻ > O²⁻ > N³⁻

Explanation: For an isoelectronic series (all having 10 electrons), ionic radius decreases as nuclear charge (Z) increases because more protons pull the electron cloud inward. Here Z(N)=7, Z(O)=8, Z(F)=9, Z(Na)=11. Thus, N³⁻ is largest and Na⁺ is smallest: N³⁻ > O²⁻ > F⁻ > Na⁺.

9What is the maximum number of electrons that can occupy a subshell with azimuthal quantum number l = 2?

A.10

B.6

C.14

D.2

Explanation: An azimuthal quantum number l = 2 corresponds to a d subshell. The number of orbitals in a subshell is 2l + 1 = 2(2) + 1 = 5. Since each orbital holds up to 2 electrons of opposite spin, the maximum electron capacity is 2(2l + 1) = 2(5) = 10 electrons.

10Why is the second ionization energy of Sodium (Na, Z = 11) significantly larger than its first ionization energy?

A.The 3s subshell is doubly degenerate and stabilizes the Na⁺ ion.

B.Sodium forms covalent bonds after losing one electron.

C.The nuclear charge decreases after losing the first valence electron.

D.The second electron must be removed from a stable, lower-shell noble gas core ([Ne]), which experiences a higher effective nuclear charge.

Explanation: Na has the electron configuration [Ne] 3s¹. Removing the first electron (IE1 = 496 kJ/mol) leaves the Na⁺ ion with the stable noble-gas configuration [Ne] (2s² 2p⁶). Removing a second electron (IE2 = 4562 kJ/mol) requires breaking into this fully-filled n=2 inner shell, which is closer to the nucleus and experiences a dramatically higher effective nuclear charge.

About the PAU Chemistry (Aragón) Exam

The Aragón PAU Chemistry exam (Química 2º Bachillerato) evaluates secondary school students across Aragón on core chemical concepts, including atomic physics, bonding theories, thermodynamics, kinetics, chemical equilibria, acid-base systems, electrochemistry, and organic chemistry. Please note: The official UNIZAR exam features written open-ended problem solving in Spanish; the 100 practice questions provided here are an English-language multiple-choice adaptation designed for self-assessment and curriculum mastery.

Exam sponsor: PAU Organising Commission of Aragón / UNIZAR. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Standardized written examination organized by the PAU Organising Commission of Aragón / UNIZAR featuring quantitative problem-solving and theoretical questions (adapted here to a 100-item English MCQ practice format).

Time Limit

90 minutes (1.5 hours)

Passing Score

Marked on a 0–10 scale. Minimum 4.0 required in Access Phase to combine with Bachillerato GPA (60% Bachillerato + 40% PAU >= 5.0 to pass).

Exam / Certification Fees

EUR 75.00 ordinary registration fee (Access Phase plus two voluntary subjects); EUR 30.93 per additional voluntary subject (UNIZAR 2026)

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Official sources

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

15%

Atomic Structure & Periodic Table

Quantum numbers (n, l, ml, ms), atomic orbital shapes, electron configurations, Aufbau principle, Pauli exclusion, Hund's rule, periodic properties (atomic radius, first ionization energy, electron affinity, electronegativity).

15%

Chemical Bonding & Molecular Structure

Ionic bond formation, lattice energy, Born-Haber thermochemical cycles, covalent bonding, Lewis structures, formal charges, VSEPR molecular geometry, valence bond theory, hybrid orbitals (sp, sp2, sp3), bond polarity, metallic bonding, and intermolecular forces (hydrogen bonding, dipole-dipole, dispersion).

15%

Thermodynamics & Thermochemistry

First law of thermodynamics, reaction enthalpy (ΔH°), standard enthalpies of formation, combustion, and neutralization, Hess's Law applications, bond enthalpies, standard entropy (ΔS°), Gibbs free energy equation (ΔG° = ΔH° - TΔS°), and spontaneity criteria.

10%

Chemical Kinetics

Reaction rates, experimental rate laws, reaction orders, rate constant units, collision theory, transition state theory, activation energy (Ea), Arrhenius equation calculations, homogeneous and heterogeneous catalysts.

15%

Chemical Equilibrium & Solubility

Reversible reactions, dynamic equilibrium, equilibrium constants (Kc, Kp) and relationship Kp = Kc(RT)^Δn, reaction quotient Qc, degree of dissociation (α), Le Chatelier's principle, solubility product Ksp, molar solubility, and common ion effect.

15%

Acid-Base Equilibria

Arrhenius and Brønsted-Lowry definitions, conjugate acid-base pairs, water autoionization Kw, pH and pOH scale, Ka and Kb, pKa and pKb, salt hydrolysis (acidic, basic, neutral salts), buffer solution mechanism, Henderson-Hasselbalch equation, and volumetric titrations.

10%

Redox Reactions & Electrochemistry

Oxidation state determination, balancing redox equations using ion-electron method in acidic and basic media, galvanic cells (anode, cathode, salt bridge), standard reduction potentials E°, electromotive force E°cell, Nernst equation, electrolytic cells, and Faraday's laws of electrolysis.

Organic Chemistry

IUPAC nomenclature for hydrocarbons (alkanes, alkenes, alkynes, aromatics) and oxygenated/nitrogenated functional groups (alcohols, ethers, aldehydes, ketones, carboxylic acids, esters, amines, amides), structural isomerism, stereoisomerism (cis-trans geometric and optical enantiomers), and organic reaction mechanisms (substitution, addition, elimination, combustion, esterification).

Preparing for the PAU Chemistry (Aragón) Exam

What You Need to Know

Passing score: Marked on a 0–10 scale. Minimum 4.0 required in Access Phase to combine with Bachillerato GPA (60% Bachillerato + 40% PAU >= 5.0 to pass).
Assessment: Standardized written examination organized by the PAU Organising Commission of Aragón / UNIZAR featuring quantitative problem-solving and theoretical questions (adapted here to a 100-item English MCQ practice format).
Time limit: 90 minutes (1.5 hours)
Exam / certification fees: EUR 75.00 ordinary registration fee (Access Phase plus two voluntary subjects); EUR 30.93 per additional voluntary subject (UNIZAR 2026) Official sources

Using Our Practice Resources

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PAU Chemistry (Aragón): Suggested Study Strategy

1Master quantitative calculations for equilibrium constants (Kc, Kp), degree of dissociation (α), and solubility products (Ksp).

2Practice balancing redox reactions systematically using the ion-electron method in both acidic and basic solutions.

3Calculate pH and pOH for strong and weak acids/bases, salt hydrolysis equilibria, and buffer solutions using Henderson-Hasselbalch.

4Use Hess's Law and ΔG° = ΔH° - TΔS° to solve thermodynamic problem sets and evaluate spontaneity conditions.

5Review IUPAC nomenclature rules for functionalized organic compounds and practice identifying structural and stereoisomers.

Frequently Asked Questions

What is the format of the official Aragón PAU Chemistry exam?

The official Aragón PAU Chemistry exam organized by UNIZAR is a 90-minute written examination in Spanish consisting of theoretical questions and multi-step quantitative calculation problems. The 100 questions here are an English-language MCQ study adaptation designed for practice.

What passing score is required for Aragón PAU Chemistry?

The exam is graded on a 0–10 scale. In the Access Phase (Fase de Acceso), a student must score at least 4.0 on the exam to combine it with their Bachillerato GPA (60% GPA + 40% PAU >= 5.0 required to pass).

What is the registration fee for the PAU exam in Aragón?

The base registration fee for the PAU Access Phase in Aragón is set by UNIZAR at EUR 75.00, with discounts available for large families (familia numerosa) and eligible categories.

Which topics carry the highest weight on the 2nd Bachillerato Chemistry exam?

Thermodynamics, Chemical Equilibrium, Acid-Base Equilibria, Chemical Bonding, and Atomic Structure each account for approximately 15% of the curriculum, with Kinetics, Electrochemistry, and Organic Chemistry forming the remaining sections.

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