Preparing for the ACS General Chemistry & Study Guide can feel challenging, but the right practice approach can make it manageable. This test is built to help you understand how questions are framed and what concepts are most important. As you progress, you’ll start noticing patterns that make answering questions easier. The key is to stay consistent, review your mistakes, and keep improving with each attempt.
Updated for 2026: This guide provides a structured approach to help you prepare effectively, understand key concepts, and practice real exam-level questions.
How to Use This Practice Test
- Start by reviewing key concepts before attempting questions
- Take the test in a timed environment
- Analyze your mistakes and revisit weak areas
Why This Practice Test Matters
This practice test is designed to simulate the real exam environment and help you identify knowledge gaps, improve accuracy, and build confidence.
| Exam Name | ACS General Chemistry Practice Exam |
|---|---|
| Exam Provider | American Chemical Society (ACS) |
| Exam Type | College-Level Standardized Chemistry Assessment |
| Total Practice Questions | 120+ Practice Questions (Updated for 2026) |
| Coverage Topics | • Atomic Structure & Periodic Trends • Chemical Bonding & Molecular Geometry • Stoichiometry & Chemical Reactions • Thermodynamics & Kinetics • Equilibrium & Acid–Base Chemistry • Solutions & Electrochemistry |
| Question Format | Multiple Choice Questions (MCQs) – Conceptual + Numerical |
| Difficulty Level | Intermediate to Advanced (Aligned with Real ACS Exam) |
| Study Tips | • Focus on conceptual understanding, not memorization • Practice calculations (stoichiometry, pH, gas laws) • Master periodic trends and bonding concepts • Review thermodynamics and equilibrium principles |
| Best For | College students preparing for ACS standardized chemistry exams |
| Updated | 2026 Latest Version |
1.
Which particle determines the identity of an element?
A. Electron
B. Neutron
C. Proton
D. Nucleus
Correct Answer: C
Explanation: The number of protons in an atom’s nucleus defines the atomic number, which uniquely identifies an element. Changing the number of protons changes the element itself, while electrons and neutrons can vary without altering elemental identity.
2.
What is the electron configuration of oxygen (Z = 8)?
A. 1s² 2s² 2p⁴
B. 1s² 2s² 2p⁶
C. 1s² 2p⁶
D. 1s² 2s² 2p³
Correct Answer: A
Explanation: Oxygen has 8 electrons. Filling orbitals in order gives 1s² (2), 2s² (2), and 2p⁴ (4). This configuration reflects Hund’s rule and the Aufbau principle.
3.
Which bond is most polar?
A. C–H
B. O–H
C. N–H
D. C–C
Correct Answer: B
Explanation: Bond polarity depends on electronegativity difference. Oxygen is much more electronegative than hydrogen, creating a strong dipole. Other bonds listed have smaller differences and are less polar.
4.
What is the molar mass of CO₂?
A. 28 g/mol
B. 32 g/mol
C. 44 g/mol
D. 46 g/mol
Correct Answer: C
Explanation: Carbon (12 g/mol) + 2 oxygens (16×2 = 32) = 44 g/mol. Molar mass is the sum of atomic masses.
5.
Which law states that volume is inversely proportional to pressure?
A. Charles’s law
B. Boyle’s law
C. Avogadro’s law
D. Dalton’s law
Correct Answer: B
Explanation: Boyle’s law states that pressure and volume are inversely related at constant temperature. Increasing pressure decreases volume and vice versa.
6.
What is the oxidation state of sulfur in SO₄²⁻?
A. +2
B. +4
C. +6
D. −2
Correct Answer: C
Explanation: Oxygen is −2 each (−8 total). The ion has a −2 charge, so sulfur must be +6 to balance: +6 + (−8) = −2.
7.
Which phase change is endothermic?
A. Freezing
B. Condensation
C. Vaporization
D. Deposition
Correct Answer: C
Explanation: Vaporization requires energy to overcome intermolecular forces, making it endothermic. The others release energy.
8.
What is the pH of a solution with [H⁺] = 1×10⁻³ M?
A. 1
B. 2
C. 3
D. 4
Correct Answer: C
Explanation: pH = −log[H⁺] → −log(10⁻³) = 3. This logarithmic relationship is key in acid-base chemistry.
9.
Which is a strong acid?
A. CH₃COOH
B. HCl
C. NH₃
D. H₂O
Correct Answer: B
Explanation: HCl fully dissociates in water, making it a strong acid. Acetic acid is weak, ammonia is a base, and water is neutral.
10.
What type of reaction is combustion?
A. Synthesis
B. Decomposition
C. Redox
D. Double replacement
Correct Answer: C
Explanation: Combustion involves oxidation of fuel and reduction of oxygen, making it a redox reaction involving electron transfer.
11.
Which gas law relates pressure, volume, and temperature?
A. Boyle’s
B. Charles’s
C. Ideal Gas Law
D. Avogadro’s
Correct Answer: C
Explanation: PV = nRT combines pressure, volume, temperature, and moles into one equation.
12.
What is the shape of CO₂?
A. Bent
B. Linear
C. Trigonal planar
D. Tetrahedral
Correct Answer: B
Explanation: CO₂ has two electron domains around carbon, leading to a linear geometry with 180° bond angle.
13.
Which intermolecular force is strongest?
A. London dispersion
B. Dipole-dipole
C. Hydrogen bonding
D. Ion-dipole
Correct Answer: D
Explanation: Ion-dipole forces involve full charges interacting with partial charges, making them stronger than other intermolecular forces listed.
14.
What is the molarity of 1 mole in 1 L?
A. 0.1 M
B. 0.5 M
C. 1 M
D. 2 M
Correct Answer: C
Explanation: Molarity = moles/volume → 1 mol / 1 L = 1 M.
15.
Which orbital holds maximum 2 electrons?
A. s
B. p
C. d
D. f
Correct Answer: A
Explanation: Each orbital holds a maximum of 2 electrons with opposite spins. The s subshell has only one orbital.
16.
Which is a heterogeneous mixture?
A. Air
B. Saltwater
C. Oil and water
D. Sugar solution
Correct Answer: C
Explanation: Oil and water form separate phases, making it heterogeneous.
17.
Which has highest electronegativity?
A. Na
B. Cl
C. F
D. O
Correct Answer: C
Explanation: Fluorine is the most electronegative element.
18.
What is Avogadro’s number?
A. 6.02×10²³
B. 3.01×10²³
C. 1.00×10²³
D. 9.11×10⁻³¹
Correct Answer: A
Explanation: It represents number of particles per mole.
19.
Which is a base?
A. HCl
B. NaOH
C. CO₂
D. H₂SO₄
Correct Answer: B
Explanation: NaOH releases OH⁻ ions, making it a base.
20.
What is the unit of pressure?
A. Mole
B. Kelvin
C. Pascal
D. Joule
Correct Answer: C
Explanation: Pascal (Pa) is SI unit of pressure.
21.
Which reaction absorbs heat?
A. Exothermic
B. Endothermic
C. Neutralization
D. Combustion
Correct Answer: B
Explanation: Endothermic reactions absorb heat from surroundings.
22.
What is the charge of an electron?
A. +1
B. −1
C. 0
D. +2
Correct Answer: B
23.
Which is noble gas?
A. O₂
B. N₂
C. Ne
D. Cl₂
Correct Answer: C
24.
What is boiling point trend?
A. Decreases down group
B. Increases with stronger IMF
C. Random
D. Always constant
Correct Answer: B
25.
Which is ionic bond?
A. H₂
B. CO₂
C. NaCl
D. CH₄
Correct Answer: C
26.
What is the formula for density?
A. m/v
B. v/m
C. m×v
D. m+v
Correct Answer: A
27.
Which law: energy conserved?
A. Boyle
B. First law of thermodynamics
C. Charles
D. Dalton
Correct Answer: B
28.
Which has lowest pH?
A. 1
B. 3
C. 7
D. 10
Correct Answer: A
29.
Which is catalyst effect?
A. Increase energy
B. Lower activation energy
C. Stop reaction
D. Increase pressure
Correct Answer: B
30.
What is SI unit of energy?
A. Watt
B. Joule
C. Pascal
D. Kelvin
Correct Answer: B
31.
Which quantum number determines the shape of an orbital?
A. n
B. l
C. mₗ
D. mₛ
Correct Answer: B
Explanation: The angular momentum quantum number (l) determines the shape of an orbital. For example, l = 0 corresponds to s orbitals (spherical), l = 1 to p orbitals (dumbbell-shaped), and higher values correspond to more complex shapes. This directly affects electron distribution in atoms.
32.
Which element has the largest atomic radius?
A. Na
B. Cl
C. F
D. O
Correct Answer: A
Explanation: Atomic radius increases down a group and decreases across a period. Sodium (Na) is lower and to the left compared to the other elements listed, meaning it has more electron shells and less effective nuclear charge pulling electrons inward, giving it the largest radius.
33.
Which compound exhibits hydrogen bonding?
A. CH₄
B. NH₃
C. CO₂
D. H₂
Correct Answer: B
Explanation: Hydrogen bonding occurs when hydrogen is bonded to highly electronegative atoms like N, O, or F. NH₃ contains N–H bonds, allowing hydrogen bonding. CH₄ and H₂ lack polarity, and CO₂ is linear and nonpolar, so they cannot form hydrogen bonds.
34.
What is the empirical formula of C₆H₁₂O₆?
A. CH₂O
B. C₂H₄O₂
C. C₃H₆O₃
D. CHO
Correct Answer: A
Explanation: The empirical formula is the simplest whole-number ratio of atoms. Dividing all subscripts by 6 gives CH₂O. This represents the simplest ratio of carbon, hydrogen, and oxygen atoms in the compound.
35.
Which gas deviates most from ideal behavior?
A. He
B. H₂
C. NH₃
D. Ne
Correct Answer: C
Explanation: Real gases deviate most when intermolecular forces are strong. NH₃ is polar and exhibits hydrogen bonding, causing significant deviation. Noble gases like He and Ne are nonpolar and behave more ideally.
36.
What is the hybridization of carbon in CH₄?
A. sp
B. sp²
C. sp³
D. dsp³
Correct Answer: C
Explanation: Carbon in methane forms four sigma bonds, requiring four hybrid orbitals. This leads to sp³ hybridization, resulting in a tetrahedral geometry with bond angles of approximately 109.5°.
37.
Which reaction type forms a precipitate?
A. Combustion
B. Single replacement
C. Double replacement
D. Decomposition
Correct Answer: C
Explanation: Double replacement reactions often produce a precipitate when two aqueous ionic compounds exchange ions and form an insoluble solid. This is a key reaction type in solubility and ionic chemistry.
38.
What is the oxidation number of nitrogen in NH₃?
A. −3
B. −2
C. +3
D. +5
Correct Answer: A
Explanation: Hydrogen has a +1 oxidation state. With three hydrogens (+3 total), nitrogen must be −3 to balance the neutral molecule. This reflects nitrogen gaining electrons in this compound.
39.
Which solution has the highest boiling point?
A. Pure water
B. 0.1 M NaCl
C. 1.0 M NaCl
D. 0.5 M glucose
Correct Answer: C
Explanation: Boiling point elevation depends on solute concentration and number of particles. NaCl dissociates into two ions, and 1.0 M provides the highest particle concentration, resulting in the greatest boiling point elevation.
40.
What is the rate law determined by?
A. Balanced equation
B. Experimental data
C. Molar mass
D. Temperature only
Correct Answer: B
Explanation: The rate law must be determined experimentally because it depends on the reaction mechanism, which is not always reflected in the balanced equation. Reaction order cannot be predicted solely from stoichiometry.
41.
Which orbital fills after 3p?
A. 3d
B. 4s
C. 4p
D. 2d
Correct Answer: B
Explanation: According to the Aufbau principle, orbitals fill in order of increasing energy. The 4s orbital is lower in energy than 3d, so it fills first after 3p.
42.
Which compound is most soluble in water?
A. C₆H₆
B. NaCl
C. CO₂
D. CH₄
Correct Answer: B
Explanation: Ionic compounds like NaCl dissolve well in water due to strong ion-dipole interactions. Nonpolar molecules like benzene and methane are poorly soluble.
43.
What is the unit of molarity?
A. mol/kg
B. mol/L
C. g/mol
D. L/mol
Correct Answer: B
Explanation: Molarity is defined as moles of solute per liter of solution, making mol/L the correct unit.
44.
Which process releases energy?
A. Melting
B. Vaporization
C. Freezing
D. Sublimation
Correct Answer: C
Explanation: Freezing releases energy as molecules form stronger intermolecular forces. It is an exothermic process.
45.
Which element is most metallic?
A. Na
B. Mg
C. Al
D. Si
Correct Answer: A
Explanation: Metallic character increases down a group and to the left. Sodium is farthest left, making it the most metallic.
46.
What is the bond angle in a tetrahedral molecule?
A. 90°
B. 109.5°
C. 120°
D. 180°
Correct Answer: B
Explanation: Tetrahedral geometry arises from four electron domains, resulting in bond angles of 109.5° to minimize repulsion.
47.
Which is a strong base?
A. NH₃
B. NaOH
C. H₂O
D. CO₂
Correct Answer: B
Explanation: NaOH completely dissociates into OH⁻ ions, making it a strong base. NH₃ is weak, and CO₂ is acidic.
48.
What is the pOH of a solution with pH = 4?
A. 4
B. 6
C. 10
D. 14
Correct Answer: C
Explanation: pH + pOH = 14 → pOH = 14 − 4 = 10.
49.
Which law relates moles and volume?
A. Boyle
B. Charles
C. Avogadro
D. Dalton
Correct Answer: C
Explanation: Avogadro’s law states that volume is directly proportional to moles at constant temperature and pressure.
50.
Which is a nonelectrolyte?
A. NaCl
B. HCl
C. Sugar
D. NaOH
Correct Answer: C
Explanation: Sugar dissolves but does not ionize in water, so it does not conduct electricity, making it a nonelectrolyte.
51.
Which has highest ionization energy?
A. Na
B. Mg
C. Al
D. Ar
Correct Answer: D
Explanation: Ionization energy increases across a period. Noble gases like argon have full shells, requiring the most energy to remove an electron.
52.
What is the shape of NH₃?
A. Linear
B. Trigonal planar
C. Trigonal pyramidal
D. Tetrahedral
Correct Answer: C
Explanation: NH₃ has three bonding pairs and one lone pair, creating a trigonal pyramidal shape due to electron pair repulsion.
53.
Which is an oxidation reaction?
A. Gain of electrons
B. Loss of electrons
C. Gain of protons
D. Loss of neutrons
Correct Answer: B
Explanation: Oxidation is defined as the loss of electrons, while reduction is the gain of electrons.
54.
Which compound has ionic bonding?
A. CO₂
B. H₂O
C. NaCl
D. NH₃
Correct Answer: C
Explanation: Ionic bonds form between metals and nonmetals. Sodium (metal) and chlorine (nonmetal) form NaCl.
55.
What is the unit of energy?
A. Pascal
B. Joule
C. Mole
D. Kelvin
Correct Answer: B
Explanation: Joule is the SI unit of energy.
56.
Which gas law applies at constant pressure?
A. Boyle
B. Charles
C. Dalton
D. Ideal
Correct Answer: B
Explanation: Charles’s law states that volume is directly proportional to temperature at constant pressure.
57.
Which has strongest IMF?
A. CH₄
B. CO₂
C. H₂O
D. O₂
Correct Answer: C
Explanation: Water forms hydrogen bonds, which are stronger than dispersion or dipole forces in other molecules listed.
58.
What is the charge of a proton?
A. −1
B. 0
C. +1
D. +2
Correct Answer: C
59.
Which is amphoteric?
A. HCl
B. NaOH
C. H₂O
D. CO₂
Correct Answer: C
Explanation: Water can act as both an acid and a base, making it amphoteric.
60.
Which process increases entropy?
A. Freezing
B. Condensation
C. Vaporization
D. Crystallization
Correct Answer: C
Explanation: Vaporization increases disorder as molecules move from liquid to gas, increasing entropy significantly.
61.
Which principle explains why electrons occupy separate orbitals before pairing?
A. Aufbau principle
B. Hund’s rule
C. Pauli exclusion principle
D. Heisenberg uncertainty principle
Correct Answer: B
Explanation: Hund’s rule states that electrons fill degenerate orbitals singly with parallel spins before pairing. This minimizes electron-electron repulsion and leads to a more stable electron configuration, especially in p, d, and f orbitals.
62.
Which element has the highest electron affinity?
A. Na
B. Cl
C. Mg
D. Ne
Correct Answer: B
Explanation: Electron affinity generally increases across a period. Chlorine strongly attracts an extra electron due to its high effective nuclear charge and nearly full valence shell, making it highly favorable energetically.
63.
Which molecule is nonpolar?
A. NH₃
B. H₂O
C. CO₂
D. SO₂
Correct Answer: C
Explanation: CO₂ is linear and symmetrical, so the bond dipoles cancel out. Even though the C=O bonds are polar, the overall molecule has no net dipole moment, making it nonpolar.
64.
Which compound has the highest lattice energy?
A. NaCl
B. KCl
C. MgO
D. LiF
Correct Answer: C
Explanation: Lattice energy increases with higher ionic charges and smaller ionic radii. Mg²⁺ and O²⁻ have charges of ±2, creating a much stronger electrostatic attraction than ±1 ions in the other compounds.
65.
What is the molecular geometry of SF₆?
A. Octahedral
B. Tetrahedral
C. Trigonal planar
D. Linear
Correct Answer: A
Explanation: SF₆ has six bonding pairs and no lone pairs around sulfur. According to VSEPR theory, this leads to an octahedral geometry with bond angles of 90°.
66.
Which process has ΔH < 0?
A. Vaporization
B. Sublimation
C. Freezing
D. Melting
Correct Answer: C
Explanation: Freezing releases heat as molecules transition from liquid to solid, forming stronger intermolecular forces. This makes it an exothermic process with negative enthalpy change.
67.
Which factor increases reaction rate?
A. Lower temperature
B. Decreased concentration
C. Increased surface area
D. Removing catalyst
Correct Answer: C
Explanation: Increasing surface area allows more particles to collide effectively, increasing reaction rate. This is especially important in heterogeneous reactions.
68.
What is the equilibrium constant expression for aA + bB ⇌ cC?
A. [A]/[B]
B. [C]/[A][B]
C. [C]^c / ([A]^a[B]^b)
D. [A]^a[B]^b / [C]^c
Correct Answer: C
Explanation: The equilibrium constant expression is based on product concentrations over reactants, each raised to their stoichiometric coefficients.
69.
Which buffer system resists pH change?
A. Strong acid + strong base
B. Weak acid + conjugate base
C. Strong acid only
D. Weak base only
Correct Answer: B
Explanation: Buffers consist of a weak acid and its conjugate base (or vice versa). They resist pH changes by neutralizing added acids or bases.
70.
Which law explains partial pressures in gas mixtures?
A. Boyle’s law
B. Charles’s law
C. Dalton’s law
D. Avogadro’s law
Correct Answer: C
Explanation: Dalton’s law states that total pressure equals the sum of partial pressures of individual gases in a mixture.
71.
Which has strongest acid strength?
A. HF
B. HCl
C. HBr
D. HI
Correct Answer: D
Explanation: Acid strength increases down the group as bond strength decreases. HI dissociates most easily, making it the strongest acid among hydrogen halides listed.
72.
Which species has unpaired electrons?
A. N₂
B. O₂
C. CO₂
D. CH₄
Correct Answer: B
Explanation: Molecular oxygen has two unpaired electrons in its π* orbitals, making it paramagnetic. This is explained by molecular orbital theory.
73.
Which process increases entropy most?
A. Solid → liquid
B. Liquid → gas
C. Gas → liquid
D. Solid → solid
Correct Answer: B
Explanation: Transition from liquid to gas greatly increases disorder, as particles move freely in the gas phase, maximizing entropy.
74.
Which is strongest intermolecular force in NH₃?
A. Dispersion
B. Dipole
C. Hydrogen bonding
D. Ion-dipole
Correct Answer: C
Explanation: NH₃ forms hydrogen bonds due to N–H bonds and lone pair electrons on nitrogen.
75.
Which reaction shifts equilibrium right?
A. Increase reactants
B. Decrease products
C. Both A and B
D. Neither
Correct Answer: C
Explanation: According to Le Chatelier’s principle, adding reactants or removing products shifts equilibrium toward product formation.
76.
What is the unit of rate constant (first order)?
A. s⁻¹
B. M⁻¹s⁻¹
C. M²s⁻¹
D. s
Correct Answer: A
Explanation: First-order rate constants have units of inverse time (s⁻¹), indicating rate depends on concentration of one reactant.
77.
Which element forms +3 ion most commonly?
A. Na
B. Mg
C. Al
D. K
Correct Answer: C
Explanation: Aluminum typically loses three electrons to form Al³⁺, achieving a stable noble gas configuration.
78.
Which is strongest oxidizing agent?
A. Na
B. Cl₂
C. Fe
D. H₂
Correct Answer: B
Explanation: Chlorine has a high electron affinity and readily gains electrons, making it a strong oxidizing agent.
79.
Which solution conducts electricity best?
A. Sugar solution
B. Distilled water
C. NaCl solution
D. Ethanol
Correct Answer: C
Explanation: NaCl dissociates into ions, allowing electrical conductivity.
80.
Which is limiting reagent?
A. Excess reactant
B. Reactant used up first
C. Catalyst
D. Product
Correct Answer: B
Explanation: The limiting reagent determines the amount of product formed because it is consumed first.
81.
Which has highest boiling point?
A. CH₄
B. NH₃
C. H₂O
D. CO₂
Correct Answer: C
Explanation: Water has strong hydrogen bonding, leading to the highest boiling point.
82.
Which orbital has highest energy?
A. 2s
B. 2p
C. 3s
D. 3p
Correct Answer: D
Explanation: Energy increases with principal quantum number and subshell type. 3p is higher than 3s and 2p.
83.
Which is conjugate base of H₂CO₃?
A. CO₃²⁻
B. HCO₃⁻
C. H₂O
D. OH⁻
Correct Answer: B
Explanation: Removing one proton from carbonic acid gives bicarbonate (HCO₃⁻).
84.
Which law relates energy and frequency?
A. Boyle
B. Planck
C. Dalton
D. Charles
Correct Answer: B
Explanation: Planck’s equation E = hf relates energy and frequency of electromagnetic radiation.
85.
Which is reducing agent?
A. Gains electrons
B. Loses electrons
C. Gains protons
D. Loses neutrons
Correct Answer: B
Explanation: Reducing agents donate electrons and are themselves oxidized.
86.
Which is strongest base?
A. NH₃
B. OH⁻
C. H₂O
D. CO₂
Correct Answer: B
Explanation: OH⁻ is a strong base due to its high affinity for protons.
87.
Which is homogeneous mixture?
A. Oil + water
B. Sand + water
C. Saltwater
D. Ice + water
Correct Answer: C
Explanation: Salt dissolves completely, forming a uniform mixture.
88.
Which has highest vapor pressure?
A. Strong IMF
B. Weak IMF
C. Ionic compounds
D. Hydrogen bonding
Correct Answer: B
Explanation: Weak intermolecular forces allow molecules to escape easily, increasing vapor pressure.
89.
Which is spontaneous process?
A. ΔG > 0
B. ΔG < 0
C. ΔH > 0
D. ΔS < 0
Correct Answer: B
Explanation: Negative Gibbs free energy indicates a spontaneous process.
90.
Which is unit of entropy?
A. J/mol·K
B. J
C. mol
D. K
Correct Answer: A
Explanation: Entropy is measured in joules per mole per kelvin, reflecting energy distribution.
91.
Which quantum number describes the orientation of an orbital?
A. n
B. l
C. mₗ
D. mₛ
Correct Answer: C
Explanation: The magnetic quantum number (mₗ) specifies the orientation of an orbital in space. While n determines energy level and l determines shape, mₗ distinguishes orbitals within a subshell, such as the three p orbitals oriented along x, y, and z axes.
92.
Which trend increases across a period?
A. Atomic radius
B. Ionization energy
C. Metallic character
D. Shielding
Correct Answer: B
Explanation: Ionization energy increases across a period due to increasing effective nuclear charge. As protons increase, electrons are held more tightly, requiring more energy to remove an electron, unlike atomic radius which decreases.
93.
Which molecule has trigonal planar geometry?
A. CH₄
B. NH₃
C. BF₃
D. H₂O
Correct Answer: C
Explanation: BF₃ has three bonding pairs and no lone pairs around boron, resulting in trigonal planar geometry with 120° bond angles according to VSEPR theory.
94.
Which compound is most polar?
A. CO₂
B. CH₄
C. NH₃
D. BF₃
Correct Answer: C
Explanation: NH₃ is polar due to its trigonal pyramidal shape and lone pair on nitrogen, creating a net dipole. CO₂ and BF₃ are symmetrical and nonpolar, while CH₄ is also nonpolar.
95.
Which has highest first ionization energy?
A. Li
B. B
C. C
D. Ne
Correct Answer: D
Explanation: Noble gases like neon have full valence shells and are very stable, requiring significant energy to remove an electron, giving them the highest ionization energies in a period.
96.
Which intermolecular force exists in all molecules?
A. Hydrogen bonding
B. Dipole-dipole
C. Ion-dipole
D. London dispersion
Correct Answer: D
Explanation: London dispersion forces arise from temporary dipoles and are present in all molecules, regardless of polarity. They are the weakest but universal intermolecular force.
97.
Which compound is a strong electrolyte?
A. Sugar
B. Ethanol
C. NaCl
D. Urea
Correct Answer: C
Explanation: NaCl fully dissociates into Na⁺ and Cl⁻ ions in solution, allowing strong electrical conductivity. Nonionic compounds like sugar and ethanol do not ionize and are nonelectrolytes.
98.
What is the oxidation state of phosphorus in PO₄³⁻?
A. +3
B. +5
C. −3
D. +2
Correct Answer: B
Explanation: Oxygen is −2 each (−8 total). The ion has a −3 charge, so phosphorus must be +5 to balance: +5 + (−8) = −3.
99.
Which law states energy cannot be created or destroyed?
A. Second law
B. First law
C. Boyle’s law
D. Charles’s law
Correct Answer: B
Explanation: The first law of thermodynamics states energy is conserved. It can change forms but cannot be created or destroyed, forming the basis of energy balance in chemical systems.
100.
Which process decreases entropy?
A. Melting
B. Vaporization
C. Condensation
D. Sublimation
Correct Answer: C
Explanation: Condensation converts gas to liquid, reducing randomness and disorder. This results in a decrease in entropy as particles become more ordered.
101.
Which gas is most ideal?
A. NH₃
B. CO₂
C. He
D. H₂O
Correct Answer: C
Explanation: Helium is a noble gas with minimal intermolecular forces and small size, making it behave closest to an ideal gas.
102.
Which reaction is endothermic?
A. Combustion
B. Freezing
C. Melting
D. Condensation
Correct Answer: C
Explanation: Melting requires energy input to overcome intermolecular forces, making it endothermic.
103.
Which is the strongest acid?
A. H₂O
B. HClO
C. HClO₄
D. HClO₂
Correct Answer: C
Explanation: Acid strength increases with more oxygen atoms in oxyacids due to increased stabilization of the conjugate base. HClO₄ is strongest.
104.
Which is conjugate acid of NH₃?
A. NH₂⁻
B. NH₄⁺
C. NH₃⁺
D. N₂
Correct Answer: B
Explanation: NH₃ gains a proton to form NH₄⁺, making it the conjugate acid.
105.
Which unit is used for concentration?
A. Pascal
B. Kelvin
C. Molarity
D. Joule
Correct Answer: C
Explanation: Molarity (mol/L) measures concentration of solute in solution.
106.
Which has highest vapor pressure?
A. Strong IMF
B. Weak IMF
C. Ionic solid
D. Hydrogen bonding
Correct Answer: B
Explanation: Weak intermolecular forces allow molecules to escape easily, increasing vapor pressure.
107.
Which is a catalyst function?
A. Increase ΔH
B. Lower activation energy
C. Increase pressure
D. Stop reaction
Correct Answer: B
Explanation: Catalysts lower activation energy, speeding up reactions without being consumed.
108.
Which is a colligative property?
A. Density
B. Color
C. Boiling point elevation
D. Reactivity
Correct Answer: C
Explanation: Colligative properties depend on number of solute particles, not identity.
109.
Which is strongest base?
A. Cl⁻
B. NH₃
C. OH⁻
D. H₂O
Correct Answer: C
Explanation: OH⁻ readily accepts protons, making it a strong base.
110.
Which is correct pH range of acids?
A. >7
B. <7
C. =7
D. >14
Correct Answer: B
Explanation: Acids have pH less than 7 due to higher H⁺ concentration.
111.
Which element has lowest electronegativity?
A. F
B. O
C. Na
D. Cl
Correct Answer: C
Explanation: Sodium is far left in periodic table, making it least electronegative.
112.
Which orbital is spherical?
A. s
B. p
C. d
D. f
Correct Answer: A
Explanation: s orbitals are spherical due to symmetrical electron distribution.
113.
Which is balanced equation?
A. H₂ + O₂ → H₂O
B. 2H₂ + O₂ → 2H₂O
C. H₂ + O₂ → 2H₂O
D. 2H₂ + 2O₂ → H₂O
Correct Answer: B
Explanation: Balancing ensures equal atoms on both sides.
114.
Which is oxidizing agent?
A. Loses electrons
B. Gains electrons
C. Gains protons
D. Loses neutrons
Correct Answer: B
Explanation: Oxidizing agents gain electrons and are reduced.
115.
Which has strongest bond?
A. Single
B. Double
C. Triple
D. Ionic
Correct Answer: C
Explanation: Triple bonds have highest bond energy due to three shared electron pairs.
116.
Which gas law uses Kelvin?
A. Boyle
B. Charles
C. Dalton
D. Avogadro
Correct Answer: B
Explanation: Charles’s law relates volume and temperature in Kelvin.
117.
Which is unit of pressure?
A. Joule
B. Pascal
C. Mole
D. Kelvin
Correct Answer: B
118.
Which process is spontaneous?
A. ΔG > 0
B. ΔG < 0
C. ΔH > 0
D. ΔS < 0
Correct Answer: B
119.
Which has strongest IMF?
A. CH₄
B. CO₂
C. H₂O
D. N₂
Correct Answer: C
120.
Which is unit of enthalpy?
A. J
B. mol
C. K
D. Pa
Correct Answer: A
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