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Chemistry Regents Exam January 2026 Paper with Step-by-Step Solutions

Access the official January 2026 Chemistry Regents Exam Paper and prepare effectively with detailed explanations, expert guidance, and step-by-step solutions. This page helps students review the complete exam, understand the structure of the Regents Chemistry test, and improve their exam performance through clear conceptual explanations.

Updated for Regents Chemistry January 2026 | Practice & Exam Review Resource
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January 2026 Chemistry Regents Exam – Overview

The Chemistry Regents Exam January 2026 evaluates students on major chemistry concepts including atomic structure, chemical bonding, stoichiometry, thermodynamics, acid-base chemistry, and equilibrium. The Regents exam is a key assessment for high school students studying chemistry in New York State.

On this page you can:

  • Access the official Chemistry Regents January 2026 exam paper
  • Review questions and practice exam-style problems
  • Learn with step-by-step solutions and explanations
  • Strengthen conceptual understanding for future Regents exams

Chemistry Regents January 2026 Exam Paper

Below is the official exam paper released by the New York State Education Department. You can scroll, zoom, and review all questions directly on this page.

Chemistry Regents Worked Solutions

Question No. 01 | Gold Foil Experiment

Which conclusion resulted directly from the gold foil experiment?
(1) Atoms are hard, indivisible spheres.
(2) Electrons in an atom are negatively charged.
(3) Atoms contain a small, dense nucleus.
(4) Electrons in an atom are in shells that have different energies.
βœ… Final Answer
Choice (3): Atoms contain a small, dense nucleus.
πŸ“Œ Regents Tip:
Connect the scientist to the discovery:
  • Dalton β†’ atoms are indivisible spheres
  • Thomson β†’ electrons exist
  • Rutherford β†’ small, dense, positive nucleus
  • Bohr β†’ electrons in energy levels

Question No. 02 | Protons, Neutrons, and Electrons

What is the number of electrons in an atom with 37 protons and 49 neutrons?
(1) 12
(2) 37
(3) 49
(4) 86
βœ… Final Answer
Choice (2): 37 electrons
πŸ“Œ Regents Tip:
Use these quick rules:
  • Protons = atomic number
  • Neutral atom: protons = electrons
  • Mass number: protons + neutrons
  • Neutrons change mass, not charge

Question No. 03 | Mass of an Electron

Which statement describes the mass of an electron?
(1) An electron has the same mass as a proton.
(2) An electron has the same mass as a neutron.
(3) An electron has much less mass than a proton.
(4) An electron has much more mass than a neutron.
βœ… Final Answer
Choice (3): An electron has much less mass than a proton.
πŸ“Œ Regents Tip:
A fast memory trick:
  • Proton β‰ˆ 1 amu
  • Neutron β‰ˆ 1 amu
  • Electron β‰ˆ almost 0 amu

Question No. 04 | Wave-Mechanical Model

In the wave-mechanical model of the atom, electrons are located in regions called
(1) spectra
(2) orbitals
(3) quanta
(4) nuclei
βœ… Final Answer
Choice (2): orbitals
πŸ“Œ Regents Tip:
Watch for these model keywords:
  • Bohr model β†’ fixed energy levels
  • Wave-mechanical model β†’ orbitals
  • Ground state β†’ lowest energy arrangement

Question No. 05 | Distinguishing Potassium and Rubidium

At STP, a sample of potassium can be differentiated from a sample of rubidium based on
(1) density
(2) phase
(3) temperature
(4) pressure
βœ… Final Answer
Choice (1): density
πŸ“Œ Regents Tip:
To identify a substance, look for a characteristic property:
  • density
  • melting point
  • boiling point
  • solubility
Do not pick temperature or pressure if the question already says the substances are under the same conditions.

Question No. 06 | Chemical Property of Chlorine

Which statement describes a chemical property of chlorine?
(1) Chlorine has an atomic radius of 100 pm.
(2) Chlorine reacts with sodium to form a salt.
(3) Chlorine has a melting point of 172 K.
(4) Chlorine is a green-yellow gas at STP.
βœ… Final Answer
Choice (2): Chlorine reacts with sodium to form a salt.
πŸ“Œ Regents Tip:
Quick way to tell the difference:
  • Physical property β†’ observed without changing identity
  • Chemical property β†’ describes ability to react and form something new
If you see the word reacts, it is usually a chemical property.

Question No. 07 | Allotropes of Oxygen

Oxygen gas, O2(g), and ozone gas, O3(g), are two forms of the element oxygen. These two forms of oxygen have
(1) the same molecular structures and the same properties
(2) the same molecular structures and different properties
(3) different molecular structures and the same properties
(4) different molecular structures and different properties
βœ… Final Answer
Choice (4): different molecular structures and different properties
πŸ“Œ Regents Tip:
When you see two forms of the same element, think allotropes.
  • Same element
  • Different molecular arrangement or structure
  • Different physical and chemical properties

Question No. 08 | Definition of a Compound

Which phrase describes two or more elements chemically combined?
(1) a mixture with a fixed proportion of elements
(2) a mixture with variable proportions of elements
(3) a compound with a fixed proportion of elements
(4) a compound with variable proportions of elements
βœ… Final Answer
Choice (3): a compound with a fixed proportion of elements
πŸ“Œ Regents Tip:
Use this quick comparison:
  • Mixture β†’ physically combined, variable composition
  • Compound β†’ chemically combined, fixed composition

Question No. 09 | Empirical Formula

Which formula is an empirical formula?
(1) N2O4
(2) N2O5
(3) N2F2
(4) N2H4
βœ… Final Answer
Choice (2): N2O5
πŸ“Œ Regents Tip:
To test for an empirical formula:
  • Look at all subscripts
  • Try dividing them by the same whole number
  • If you can reduce them, it is not empirical
  • If you cannot reduce them, it is empirical

Question No. 10 | Categories of Compounds

Which terms represent two different categories of compounds?
(1) covalent and molecular
(2) covalent and electrical
(3) ionic and molecular
(4) ionic and electrical
βœ… Final Answer
Choice (3): ionic and molecular
πŸ“Œ Regents Tip:
Remember this shortcut:
  • Ionic compound β†’ metal + nonmetal
  • Molecular compound β†’ nonmetal + nonmetal
  • Covalent usually means molecular bonding

Question No. 11 | Multiple Covalent Bond

Which element has molecules that each contain a multiple covalent bond?
(1) bromine
(2) hydrogen
(3) iodine
(4) oxygen
βœ… Final Answer
Choice (4): oxygen
πŸ“Œ Regents Tip:
Common elemental molecules to remember:
  • H2, N2, O2, F2, Cl2, Br2, I2
  • O2 has a double bond
  • N2 has a triple bond
  • H2, F2, Cl2, Br2, I2 have single bonds

Question No. 12 | Asymmetrical Molecule

Which formula represents an asymmetrical molecule?
(1) HCl
(2) CO2
(3) Cl2
(4) CH4
βœ… Final Answer
Choice (1): HCl
πŸ“Œ Regents Tip:
Symmetrical molecules usually have balanced shapes like:
  • CO2 β†’ linear and balanced
  • CH4 β†’ tetrahedral and balanced
  • HCl β†’ two different atoms, so asymmetrical

Question No. 13 | Gaining an Electron

Which changes in charge and radius occur when an atom gains one electron?
(1) A negative ion forms with a radius smaller than the atom.
(2) A negative ion forms with a radius larger than the atom.
(3) A positive ion forms with a radius smaller than the atom.
(4) A positive ion forms with a radius larger than the atom.
βœ… Final Answer
Choice (2): A negative ion forms with a radius larger than the atom.
πŸ“Œ Regents Tip:
Quick ion-size rule:
  • Lose electrons β†’ positive ion β†’ smaller radius
  • Gain electrons β†’ negative ion β†’ larger radius

Question No. 14 | Bond Formation and Energy

Given the equation representing a reaction:
N + N β†’ N2
What occurs during this reaction?
(1) Energy is absorbed as bonds are broken.
(2) Energy is absorbed as bonds are formed.
(3) Energy is released as bonds are broken.
(4) Energy is released as bonds are formed.
βœ… Final Answer
Choice (4): Energy is released as bonds are formed.
πŸ“Œ Regents Tip:
Memorize this pair:
  • Breaking bonds β†’ absorbs energy
  • Forming bonds β†’ releases energy

Question No. 15 | Ionic and Covalent Bonds in One Compound

Which compound has both ionic and covalent bonds?
(1) CaCl2
(2) KClO2
(3) Li2S
(4) MnO2
βœ… Final Answer
Choice (2): KClO2
πŸ“Œ Regents Tip:
If you see a metal + polyatomic ion, think:
  • Ionic bond between the metal and the ion
  • Covalent bonds inside the polyatomic ion

Question No. 16 | Cannot Be Broken Down Chemically

Which substance can not be broken down by a chemical change?
(1) Fe
(2) Fe2O3
(3) FeSO4
(4) Fe2(SO4)3
βœ… Final Answer
Choice (1): Fe
πŸ“Œ Regents Tip:
Quick rule:
  • Element β†’ cannot be broken down chemically
  • Compound β†’ can be broken down chemically

Question No. 17 | Kinetic Molecular Theory

According to the kinetic molecular theory, the particles of an ideal gas have
(1) collisions that do not transfer energy
(2) strong attractive forces between them
(3) random, constant, straight-line motion
(4) large volumes compared to the distances between them
βœ… Final Answer
Choice (3): random, constant, straight-line motion
πŸ“Œ Regents Tip:
Kinetic molecular theory keywords:
  • random motion
  • constant motion
  • straight-line motion
  • elastic collisions
  • very weak attractions

Question No. 18 | Collision Theory

In order for a chemical reaction to occur, colliding particles must have proper orientation and proper
(1) radii
(2) energy
(3) molar masses
(4) oxidation states
βœ… Final Answer
Choice (2): energy
πŸ“Œ Regents Tip:
Think: successful collision = right direction + enough energy.

Question No. 19 | Same Number of Atoms

At STP, which sample of gas has the same number of atoms as 4.0 liters of Ne gas?
(1) 8.0 L of Ar(g)
(2) 2.0 L of He(g)
(3) 3.0 L of Kr(g)
(4) 4.0 L of Xe(g)
βœ… Final Answer
Choice (4): 4.0 L of Xe(g)
πŸ“Œ Regents Tip:
For noble gases:
  • particles = atoms
  • same T and P + same volume = same number of atoms

Question No. 20 | Exothermic Dissolving

Based on Table I, the dissolving of which compound is an exothermic process at 298 K and 101.3 kPa?
(1) KNO3(s)
(2) NaOH(s)
(3) NH4Cl(s)
(4) NH4NO3(s)
βœ… Final Answer
Choice (2): NaOH(s)
πŸ“Œ Regents Tip:
Common endothermic dissolving substances to remember:
  • KNO3
  • NH4Cl
  • NH4NO3
A classic exothermic one is NaOH.

Question No. 21 | Heat of Reaction Formula

Which expression represents the heat of reaction for a chemical change in terms of potential energy, PE?
(1) PE of products Γ— PE of reactants
(2) PE of products Γ· PE of reactants
(3) PE of products + PE of reactants
(4) PE of products βˆ’ PE of reactants
βœ… Final Answer
Choice (4): PE of products βˆ’ PE of reactants
πŸ“Œ Regents Tip:
Always write:
  • Ξ”H = PE(products) βˆ’ PE(reactants)

Question No. 22 | How a Catalyst Works

Which phrase describes how a catalyst increases the rate of a chemical reaction?
(1) provides an alternate reaction pathway
(2) provides an alternate energy source
(3) increases the potential energy of the reactants
(4) increases the activation energy of the reaction
βœ… Final Answer
Choice (1): provides an alternate reaction pathway
πŸ“Œ Regents Tip:
Catalyst = alternate path + lower activation energy.

Question No. 23 | Greatest Entropy

At standard pressure, which 5.0-gram sample of xenon has the greatest entropy?
(1) Xe(s) at 161 K
(2) Xe(l) at 161 K
(3) Xe(l) at 165 K
(4) Xe(g) at 165 K
βœ… Final Answer
Choice (4): Xe(g) at 165 K
πŸ“Œ Regents Tip:
Entropy trend:
  • solid β†’ lowest entropy
  • liquid β†’ medium entropy
  • gas β†’ highest entropy
  • higher temperature β†’ greater entropy

Question No. 24 | Natural Changes in Systems

Systems in nature tend to undergo changes that result in
(1) lower energy and less disorder
(2) higher energy and less disorder
(3) lower energy and greater disorder
(4) higher energy and greater disorder
βœ… Final Answer
Choice (3): lower energy and greater disorder
πŸ“Œ Regents Tip:
Nature tends to favor:
  • lower energy
  • greater disorder
  • higher entropy

Question No. 25 | Homologous Series Formula

Which compound is a member of the homologous series represented by the general formula CnH2n?
(1) C2H2
(2) C3H6
(3) C4H10
(4) C5H8
βœ… Final Answer
Choice (2): C3H6
πŸ“Œ Regents Tip:
Common organic general formulas:
  • Alkanes: CnH2n+2
  • Alkenes / cycloalkanes: CnH2n
  • Alkynes: CnH2nβˆ’2

Question No. 26 | Reaction That Produces an Alcohol

Which term identifies a reaction that produces an alcohol?
(1) combustion
(2) deposition
(3) fermentation
(4) sublimation
βœ… Final Answer
Choice (3): fermentation
πŸ“Œ Regents Tip:
Remember this organic chemistry fact:
  • Fermentation β†’ produces ethanol
  • Ethanol is an alcohol

Question No. 27 | Identifying an Electrolyte

Which statement describes a substance that is an electrolyte?
(1) The substance conducts an electric current and cannot dissolve in water.
(2) The substance cannot conduct an electric current and cannot dissolve in water.
(3) When the substance dissolves in water, the solution can conduct an electric current.
(4) When the substance dissolves in water, the solution cannot conduct an electric current.
βœ… Final Answer
Choice (3): When the substance dissolves in water, the solution can conduct an electric current.
πŸ“Œ Regents Tip:
Think of an electrolyte this way:
  • Dissolves in water
  • Forms ions
  • Solution conducts electricity

Question No. 28 | Arrhenius Acid

Which substance is an Arrhenius acid?
(1) NH3
(2) HNO3
(3) NaCl
(4) NaOH
βœ… Final Answer
Choice (2): HNO3
πŸ“Œ Regents Tip:
Quick acid-base check:
  • Arrhenius acid β†’ produces H+ in water
  • Arrhenius base β†’ produces OHβˆ’ in water

Question No. 29 | Splitting a Heavy Nucleus

A heavy nucleus splits into two lighter nuclei during which process?
(1) decomposition
(2) deposition
(3) fission
(4) fusion
βœ… Final Answer
Choice (3): fission
πŸ“Œ Regents Tip:
Nuclear memory trick:
  • Fission β†’ one big nucleus splits
  • Fusion β†’ small nuclei join together

Question No. 30 | Fusion in the Sun

The energy released by nuclear fusion in the Sun results from the conversion of
(1) energy to matter
(2) matter to energy
(3) atoms to molecules
(4) molecules to atoms
βœ… Final Answer
Choice (2): matter to energy
πŸ“Œ Regents Tip:
For nuclear reactions, remember:
  • A little mass can turn into a lot of energy
  • This is the idea behind E = mcΒ²
  • Fusion in the Sun is a classic example of matter β†’ energy

Question No. 31 | Lithium in an Excited State

Which electron configuration represents a lithium atom in an excited state?
(1) 2-1
(2) 2-2
(3) 1-2-1
(4) 1-1-1
βœ… Final Answer
Choice (4): 1-1-1
πŸ“Œ Regents Tip:
For excited-state electron configurations:
  • Keep the same total number of electrons
  • Look for an electron moved to a higher shell
  • Do not confuse ground state with excited state

Question No. 32 | Lewis Electron-Dot Diagram for Selenium

Which Lewis electron-dot diagram represents an atom of selenium in the ground state?
(1)
(2)
(3)
(4)
In the provided image, the correct diagram is the one showing 6 valence electrons around Se.
βœ… Final Answer
Choice (3)
πŸ“Œ Regents Tip:
For main-group elements:
  • Group 1 β†’ 1 valence electron
  • Group 2 β†’ 2 valence electrons
  • Group 13–18 β†’ 3 to 8 valence electrons
  • Group 16 elements like Se always have 6 valence electrons

Question No. 33 | Oxide Formula Xβ‚‚O

Which element could be represented by the X in the oxide formula, X2O?
(1) Cd
(2) Cr
(3) Ca
(4) Cs
βœ… Final Answer
Choice (4): Cs
πŸ“Œ Regents Tip:
When working with formulas:
  • Oxide always has charge βˆ’2
  • Use the subscripts to figure out the ion charges
  • Group 1 metals usually form +1 ions

Question No. 34 | Naming PdO

What is a chemical name for the compound PdO?
(1) palladium (II) oxide
(2) palladium (IV) oxide
(3) palladium peroxide
(4) palladium hydroxide
βœ… Final Answer
Choice (1): palladium (II) oxide
πŸ“Œ Regents Tip:
For transition metals:
  • Find the charge first
  • Use a Roman numeral in the name
  • Example: FeO = iron(II) oxide

Question No. 35 | Mass Conservation in a Reaction

Given the balanced equation representing a reaction:
CH4(g) + 2O2(g) β†’ 2H2O(β„“) + CO2(g) + 890.4 kJ
When 12 grams of CH4(g) react completely with 48 grams of O2(g) to produce 33 grams of CO2(g), how many grams of H2O(β„“) are produced?
(1) 12 g
(2) 27 g
(3) 60 g
(4) 69 g
βœ… Final Answer
Choice (2): 27 g
πŸ“Œ Regents Tip:
For mass problems:
  • Total reactant mass = total product mass
  • If one product mass is missing, subtract from the total

Question No. 36 | Gram-Formula Mass of Pβ‚‚Oβ‚…

What is the gram-formula mass of P2O5?
(1) 47 g/mol
(2) 111 g/mol
(3) 142 g/mol
(4) 187 g/mol
βœ… Final Answer
Choice (3): 142 g/mol
πŸ“Œ Regents Tip:
To find gram-formula mass:
  • Multiply each element’s atomic mass by its subscript
  • Add all the results together

Question No. 37 | Same Electron Configuration as Neon

In the ground state, ions of which two elements each have the same electron configuration as an atom of neon in the ground state?
(1) lithium and fluorine
(2) sodium and chlorine
(3) magnesium and oxygen
(4) calcium and sulfur
βœ… Final Answer
Choice (3): magnesium and oxygen
πŸ“Œ Regents Tip:
Noble gas configurations are very common in ions:
  • Metals lose electrons to match a noble gas
  • Nonmetals gain electrons to match a noble gas
  • Neon configuration = 10 electrons

Question No. 38 | Particle Model of Fluorine at STP

Which particle model diagram represents a sample of fluorine at STP?
(1)
(2)
(3)
(4)
Fluorine at STP exists as F2(g), which means it is a diatomic gas made of identical atoms.
βœ… Final Answer
Choice (1)
πŸ“Œ Regents Tip:
For particle diagrams:
  • Gas β†’ particles far apart
  • Diatomic element β†’ atoms in pairs
  • Same element β†’ same type/color of atoms

Question No. 39 | Most Soluble Compound in Water

Based on Table F, which compound is most soluble in water?
(1) Ag2CrO4
(2) AgNO3
(3) CuCO3
(4) Cu3(PO4)2
βœ… Final Answer
Choice (2): AgNO3
πŸ“Œ Regents Tip:
Memorize these from Table F:
  • All nitrates are soluble
  • Carbonates are usually insoluble
  • Phosphates are usually insoluble
  • Chromates are usually insoluble except with Group 1 or NH4+

Question No. 40 | Lowest Freezing Point

Which solution has the lowest freezing point?
(1) 1.0 M NaCl(aq)
(2) 1.0 M C6H12O6(aq)
(3) 2.0 M NaCl(aq)
(4) 2.0 M C6H12O6(aq)
βœ… Final Answer
Choice (3): 2.0 M NaCl(aq)
πŸ“Œ Regents Tip:
For colligative properties:
  • More particles = lower freezing point
  • Electrolytes make more particles than nonelectrolytes
  • Higher molarity = more particles

Question No. 41 | Heat Needed to Vaporize Water

What is the amount of heat energy required to completely vaporize a 12.5-gram sample of H2O(β„“) at 373 K and 1.0 atmosphere?
(1) 4180 J
(2) 5230 J
(3) 19 500 J
(4) 28 300 J
βœ… Final Answer
Choice (4): 28 300 J
πŸ“Œ Regents Tip:
For phase-change energy:
  • Melting/freezing: q = mHf
  • Boiling/condensing: q = mHv
  • No temperature change during the phase change

Question No. 42 | Fastest Reaction Rate

A 2.0-gram sample of solid iron, Fe(s), reacts with 25 mL of 0.10 M HCl(aq). Which conditions will produce the fastest reaction rate?
(1) powdered iron at 273 K
(2) powdered iron at 303 K
(3) strip of iron at 273 K
(4) strip of iron at 303 K
βœ… Final Answer
Choice (2): powdered iron at 303 K
πŸ“Œ Regents Tip:
Reaction rate increases with:
  • higher temperature
  • greater surface area
  • higher concentration
  • presence of a catalyst

Question No. 43 | System in a Sealed Flask of Water

Which term describes a system with a sealed 100.-mL flask that contains 50. grams of water at 25Β°C?
(1) physical equilibrium, only
(2) chemical equilibrium, only
(3) condensation, only
(4) evaporation, only
βœ… Final Answer
Choice (1): physical equilibrium, only
πŸ“Œ Regents Tip:
If a liquid is in a sealed container:
  • evaporation happens
  • condensation happens
  • eventually the two rates become equal
  • that is physical equilibrium

Question No. 44 | Time When Equilibrium Is Reached

Given the equation and graph representing a reaction:
N2O4(g) β‡Œ 2NO2(g)
At which time is the system at equilibrium?
(1) 12 s
(2) 22 s
(3) 50. s
(4) 70. s
βœ… Final Answer
Choice (4): 70. s
πŸ“Œ Regents Tip:
On a concentration-versus-time graph:
  • equilibrium does not mean equal concentrations
  • equilibrium means constant concentrations
  • look for the flat, horizontal part of the graph

Question No. 45 | Temperature Change and Equilibrium Shift

Given the equation representing a chemical system at equilibrium in a sealed, rigid container:
H2(g) + I2(g) + energy β‡Œ 2HI(g)
When the temperature of the system in the container is increased, the equilibrium shifts to the
(1) right and the concentration of HI(g) decreases
(2) right and the concentration of HI(g) increases
(3) left and the concentration of HI(g) decreases
(4) left and the concentration of HI(g) increases
βœ… Final Answer
Choice (2): right and the concentration of HI(g) increases
πŸ“Œ Regents Tip:
For equilibrium and heat:
  • If heat is on the left, forward reaction is endothermic
  • If temperature increases, equilibrium shifts to use the added heat
  • Shift right β†’ product concentration increases

Question No. 46 | Naming an Organic Compound

Given the structural formula shown, what is a chemical name for this compound?
(1) 4-methylhexane
(2) 3-methylhexane
(3) 3,4-dimethylpentane
(4) 2,3-dimethylpentane
βœ… Final Answer
Choice (4): 2,3-dimethylpentane
πŸ“Œ Regents Tip:
For organic naming:
  • Always choose the longest continuous carbon chain
  • Then identify the branches
  • Number the chain to give the branches the lowest possible numbers
  • If there are 2 identical branches, use the prefix di-

Question No. 47 | Oxidation State of Chlorine

What is the oxidation state of chlorine in the compound KClO3?
(1) +1
(2) βˆ’1
(3) +5
(4) +7
βœ… Final Answer
Choice (3): +5
πŸ“Œ Regents Tip:
For oxidation-number questions:
  • Group 1 metals are always +1
  • Oxygen is usually βˆ’2
  • The total oxidation numbers in a neutral compound must add up to 0

Question No. 48 | Acid-Base Theory and the Reverse Reaction

Given the equation representing a reversible reaction:
NH3(g) + H2O(β„“) β‡Œ NH4+(aq) + OHβˆ’(aq)
According to one acid-base theory, the reactant in the reverse reaction that donates an H+ ion is
(1) NH3(g)
(2) H2O(β„“)
(3) NH4+(aq)
(4) OHβˆ’(aq)
βœ… Final Answer
Choice (3): NH4+(aq)
πŸ“Œ Regents Tip:
For BrΓΈnsted-Lowry acids and bases:
  • Acid = H+ donor
  • Base = H+ acceptor
  • In a reversible reaction, the roles can switch in the reverse direction

Question No. 49 | Change in Hydronium Ion Concentration

When the pH value of a solution is changed from 4.0 to 7.0, what is the change in the concentration of hydronium ions?
(1) decreased by a factor of 1000
(2) decreased by a factor of 3
(3) increased by a factor of 1000
(4) increased by a factor of 3
βœ… Final Answer
Choice (1): decreased by a factor of 1000
πŸ“Œ Regents Tip:
On the pH scale:
  • Each pH change of 1 = factor of 10
  • Higher pH = lower [H3O+]
  • Lower pH = higher [H3O+]

Question No. 50 | Identifying a Radioactive Emission

The diagram represents a radioactive emission from a sample of chromium-51 passing through an electric field between two oppositely charged metal plates. Which type of radioactive emission is represented in the diagram?
(1) alpha particle
(2) beta particle
(3) gamma radiation
(4) positron
βœ… Final Answer
Choice (3): gamma radiation
πŸ“Œ Regents Tip:
Quick comparison of radioactive emissions:
  • Alpha β†’ positive, deflects one way
  • Beta β†’ negative, deflects the opposite way
  • Gamma β†’ neutral, goes straight
  • Positron β†’ positive, deflects like alpha

Question No. 51 | Percent Composition by Mass

Determine the percent composition by mass of Cu in CuSO4 (gram-formula mass = 160. g/mol).
βœ… Final Answer
39.7% Cu   (about 40.0%)
πŸ“Œ Regents Tip:
For percent composition:
  • Use part Γ· whole Γ— 100
  • The β€œpart” is the mass of the element you are asked about
  • The β€œwhole” is the total gram-formula mass of the compound

Question No. 52 | Why K-39 and K-40 Are Isotopes

State, in terms of both protons and neutrons, why an atom of K-39 is an isotope of an atom of K-40.
βœ… Final Answer
They have the same number of protons but different numbers of neutrons.
πŸ“Œ Regents Tip:
Isotopes always:
  • belong to the same element
  • have the same atomic number
  • have different mass numbers because the neutrons differ

Question No. 53 | Electron Energy in Different Shells

Compare the energy of an electron in the first shell of a potassium atom to the energy of an electron in the fourth shell of the same atom.
βœ… Final Answer
An electron in the first shell has less energy than an electron in the fourth shell.
πŸ“Œ Regents Tip:
As you move to shells farther from the nucleus:
  • electron energy increases
  • electrons are held less tightly

Question No. 54 | Numerical Setup for Atomic Mass of Potassium

Show a numerical setup for calculating the atomic mass of potassium.
βœ… Final Answer
(38.964)(0.9326) + (39.964)(0.0001) + (40.962)(0.0673)
πŸ“Œ Regents Tip:
Weighted average formula:
  • mass Γ— decimal abundance
  • then add all isotope contributions
  • do not use the percent directly unless you divide by 100 at the end

Question No. 55 | Why the Equation Is Balanced

Given the balanced equation:
N2(g) + 3H2(g) β†’ 2NH3(g) + 91.8 kJ
State, in terms of the number of each type of atom, why the equation is balanced.
βœ… Final Answer
There are 2 nitrogen atoms and 6 hydrogen atoms on each side of the equation.
πŸ“Œ Regents Tip:
A balanced equation must have:
  • the same number of each kind of atom on both sides
  • coefficients changed, not subscripts

Question No. 56 | Evidence the Reaction Is Exothermic

State evidence from the equation that the reaction is exothermic.
N2(g) + 3H2(g) β†’ 2NH3(g) + 91.8 kJ
βœ… Final Answer
The 91.8 kJ is on the product side, so energy is released.
πŸ“Œ Regents Tip:
Heat in equations:
  • energy on the right β†’ exothermic
  • energy on the left β†’ endothermic

Question No. 57 | Moles of Hydrogen Required

Determine the number of moles of hydrogen gas required to react completely with nitrogen gas to produce 10.0 moles of ammonia gas in this reaction.
N2(g) + 3H2(g) β†’ 2NH3(g) + 91.8 kJ
βœ… Final Answer
15.0 mol H2
πŸ“Œ Regents Tip:
For mole-mole conversions:
  • always start with the balanced equation
  • use the coefficients as the mole ratio

Question No. 58 | Significant Figures in 300. K

State the number of significant figures used to express the original temperature of the sample of nitrogen gas.
Original temperature = 300. K
βœ… Final Answer
3 significant figures
πŸ“Œ Regents Tip:
Sig fig shortcut:
  • 300 usually has 1 sig fig
  • 300. has 3 sig figs
  • 300.0 has 4 sig figs

Question No. 59 | Force of Collisions at 300 K vs 450 K

Compare the force of collisions of the gas particles at 300. K to the force of collisions at 450. K.
βœ… Final Answer
The collisions at 300 K are less forceful than at 450 K.
πŸ“Œ Regents Tip:
Temperature and particles:
  • higher temperature β†’ faster particles
  • faster particles β†’ more forceful collisions

Question No. 60 | Conditions for More Ideal Gas Behavior

State a change in temperature and a change in pressure of the nitrogen gas that will cause the gas in the cylinder to behave more like an ideal gas.
βœ… Final Answer
Increase the temperature and decrease the pressure.
πŸ“Œ Regents Tip:
Real gases are most ideal at:
  • high temperature
  • low pressure

Question No. 61 | Combined Gas Law Volume Calculation

Determine the volume of the N2 gas if the temperature is changed to 450. K and the pressure is changed to 60.0 kPa.
Initial conditions: V1 = 320. mL, T1 = 300. K, P1 = 100. kPa
βœ… Final Answer
800. mL
πŸ“Œ Regents Tip:
For combined gas law problems:
  • temperature must be in Kelvin
  • match pressure units on both sides
  • solve algebra first, then substitute carefully

Question No. 62 | Class of Compound for Reactant 1

Based on Table R, write the name of the class of compound to which reactant 1 belongs.
Reactant 1 is shown as HCOOH, which is methanoic acid.
βœ… Final Answer
Organic acid
πŸ“Œ Regents Tip:
Common Table R clue:
  • –COOH β†’ organic acid
  • –OH β†’ alcohol
  • –COO– β†’ ester

Question No. 63 | Element That Makes Reactant 2 Organic

Identify the element in reactant 2 that allows it to be classified as an organic compound.
Reactant 2 is ethanol, CH3CH2OH.
βœ… Final Answer
Carbon
πŸ“Œ Regents Tip:
Organic chemistry almost always centers around carbon-containing compounds.

Question No. 64 | Electrons Shared Between Carbon Atoms

State the number of electrons shared between the carbon atoms in reactant 2.
Reactant 2 is CH3CH2OH.
βœ… Final Answer
2 electrons
πŸ“Œ Regents Tip:
Bond-electron quick rule:
  • single bond = 2 electrons
  • double bond = 4 electrons
  • triple bond = 6 electrons

Question No. 65 | Why Propanoic Acid and Ethyl Methanoate Are Isomers

State, in terms of molecular formulas and structural formulas, why propanoic acid, CH3CH2COOH, is an isomer of ethyl methanoate, HCOOCH2CH3.
βœ… Final Answer
They have the same molecular formula, C3H6O2, but different structural formulas.
πŸ“Œ Regents Tip:
Always separate these two ideas:
  • Molecular formula = how many of each type of atom
  • Structural formula = how the atoms are connected
Same formula + different arrangement = isomers.

Topics Covered in the Chemistry Regents Exam

The Regents Chemistry exam assesses a wide range of topics typically covered in high school chemistry courses. Students preparing for the January 2026 exam should review the following major concepts:

  • Atomic structure and periodic trends
  • Chemical bonding and molecular geometry
  • Stoichiometry and mole calculations
  • Chemical reactions and reaction types
  • Acids, bases, and pH calculations
  • Energy changes and thermochemistry
  • Equilibrium and reaction rates
  • Electrochemistry and redox reactions

How to Use This Exam Paper for Effective Practice

To maximize your preparation for the Regents Chemistry exam, follow this recommended study approach:

1. Attempt the Questions First

Try solving each question independently before checking any solutions. This helps build exam confidence and improves problem-solving skills.

2. Analyze Step-by-Step Solutions

Review detailed explanations to understand the reasoning behind each answer. Focus on chemical principles rather than memorizing answers.

3. Identify Weak Areas

Track topics where mistakes occur frequently and review those concepts in your chemistry notes or textbooks.

4. Practice Similar Problems

Use additional Regents practice exams to strengthen problem-solving speed and accuracy.

Frequently Asked Questions – Chemistry Regents Exam

What topics appear on the Chemistry Regents exam?
Major topics include atomic structure, chemical bonding, stoichiometry, thermochemistry, acids and bases, equilibrium, and electrochemistry.
Is the January Regents exam easier than the June exam?
The difficulty level is designed to be similar across all Regents administrations. However, specific questions may vary in complexity.
How can I improve my Regents Chemistry score?
Practice previous Regents exams, review reference tables carefully, and focus on understanding core chemistry concepts.