New York State Regents Examinations Physical Setting / Chemistry (Regents Examination) Syllabus

Write the correct formula for aluminum oxide using oxidation numbers.

Al is +3 and O is -2; crossing charges gives Al2O3.

What is a polyatomic ion? Give the formulas and charges of nitrate, sulfate, and ammonium.

A polyatomic ion is a charged group of covalently bonded atoms acting as a unit. Nitrate = NO3⁻, sulfate = SO4²⁻, ammonium = NH4⁺.

According to VSEPR theory, why is a water (H2O) molecule bent rather than linear?

The central oxygen has two bonding pairs and two lone pairs of electrons; the lone pairs repel the bonding pairs, pushing the H atoms into a bent shape.

What molecular shapes result from a central atom with (a) 2 bonds and no lone pairs and (b) 4 bonds and no lone pairs?

(a) Linear (e.g., CO2); (b) tetrahedral (e.g., CH4).

What makes a whole molecule polar versus nonpolar?

A molecule is polar if it has polar bonds arranged asymmetrically so the dipoles do not cancel (e.g., H2O). It is nonpolar if it has no polar bonds or if symmetrical shape causes the dipoles to cancel (e.g., CO2, CH4).

What is hydrogen bonding and why does it give water its unusually high boiling point?

Hydrogen bonding is a strong intermolecular attraction between H bonded to N, O, or F in one molecule and a lone pair on N, O, or F in another. These strong attractions require extra energy to separate molecules, raising water's boiling point.

What is the value of one mole (Avogadro's number), and what does it represent?

One mole = 6.02 × 10²³ representative particles (atoms, molecules, ions, or formula units).

How do you calculate the gram-formula mass (molar mass) of a compound? Find it for H2O.

Add the atomic masses of all atoms in the formula. For H2O: (2 × 1) + 16 = 18 g/mol.

What is the formula relating moles, mass, and gram-formula mass?

moles = mass (in grams) ÷ gram-formula mass (g/mol), often written n = m / GFM.

How many moles are in 36 grams of water (GFM = 18 g/mol)?

moles = 36 g ÷ 18 g/mol = 2 moles.

What does it mean to balance a chemical equation, and what law requires it?

Balancing means making the number of atoms of each element equal on both sides by adjusting coefficients. It is required by the Law of Conservation of Mass (matter cannot be created or destroyed).

Balance the equation: H2 + O2 → H2O.

2H2 + O2 → 2H2O.

In a balanced equation, may you change subscripts to balance atoms?

No. Only coefficients (the numbers in front of formulas) may be changed; changing subscripts would change the identity of the substance.

In the reaction N2 + 3H2 → 2NH3, how many moles of NH3 are produced from 6 moles of H2?

The mole ratio of H2 to NH3 is 3:2, so 6 mol H2 × (2 mol NH3 / 3 mol H2) = 4 moles NH3.

What is a mole ratio and where does it come from?

A mole ratio is the proportion between amounts of two substances in a reaction; it comes from the coefficients of the balanced chemical equation.

Compare the particle arrangement, energy, and shape/volume of solids, liquids, and gases.

Solids: tightly packed, lowest energy, fixed shape and volume. Liquids: close but mobile, medium energy, fixed volume but take container's shape. Gases: far apart, highest energy, no fixed shape or volume.

Name the phase changes for: solid→liquid, liquid→gas, gas→liquid, solid→gas, and liquid→solid.

Solid→liquid = melting (fusion); liquid→gas = vaporization/boiling; gas→liquid = condensation; solid→gas = sublimation; liquid→solid = freezing.

Why does temperature stay constant during a phase change even though heat is being added?

The added energy is used to overcome the attractive forces between particles (changing potential energy/breaking intermolecular attractions) rather than increasing kinetic energy, so temperature does not change until the phase change is complete.

State Boyle's Law and its mathematical relationship.

At constant temperature, the volume of a gas is inversely proportional to its pressure: P1V1 = P2V2.

State Charles's Law and the temperature scale it must use.

At constant pressure, the volume of a gas is directly proportional to its absolute (Kelvin) temperature: V1/T1 = V2/T2. Temperature must be in Kelvin.

What is the combined gas law equation?

P1V1/T1 = P2V2/T2, with temperature in Kelvin.

What are the assumptions of an ideal gas, and under what conditions do real gases behave most ideally?

Ideal gas particles have no volume and no attractive forces, and collisions are perfectly elastic. Real gases behave most ideally at high temperature and low pressure.

Define solute, solvent, and solution.

A solute is the substance being dissolved; a solvent is the substance doing the dissolving (present in greater amount); a solution is the resulting homogeneous mixture.

How does temperature affect the solubility of most solids versus most gases in water?

For most solids, solubility increases as temperature increases; for gases, solubility decreases as temperature increases.

What is the difference between a saturated, unsaturated, and supersaturated solution?

Unsaturated: can dissolve more solute. Saturated: holds the maximum solute at that temperature (equilibrium). Supersaturated: holds more than the normal maximum and is unstable.

How do dissolved solutes affect the boiling point and freezing point of a solvent?

Adding a solute raises the boiling point (boiling point elevation) and lowers the freezing point (freezing point depression) of the solvent.

What is the difference between an exothermic and an endothermic reaction in terms of heat and the sign of ΔH?

Exothermic reactions release heat to the surroundings and have a negative ΔH; endothermic reactions absorb heat and have a positive ΔH.

What is heat of reaction (ΔH) and how is it found from a potential energy diagram?

ΔH is the difference in potential energy between the products and the reactants (ΔH = PE of products − PE of reactants). A drop in PE means exothermic; a rise means endothermic.

What is activation energy?

The minimum amount of energy reactant particles must have for a successful collision that leads to a reaction; it is the energy needed to reach the activated complex (top of the PE hump).

According to collision theory, what four factors increase the rate of a chemical reaction?

Increasing concentration, increasing temperature, increasing surface area, and adding a catalyst all increase reaction rate by increasing the frequency and/or effectiveness of collisions.

How does a catalyst speed up a reaction?

A catalyst provides an alternative reaction pathway with a lower activation energy, without being consumed in the reaction; it does not change ΔH.

What is dynamic equilibrium in a reversible reaction?

The state in which the forward and reverse reactions occur at equal rates, so the concentrations of reactants and products remain constant (though the reactions continue).

State Le Chatelier's Principle.

When a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, the equilibrium shifts in the direction that relieves the stress.

For an equilibrium, what is the effect of increasing the concentration of a reactant?

The equilibrium shifts to the right (toward products) to consume the added reactant and relieve the stress.

What is entropy?

Entropy (S) is a measure of the disorder or randomness of a system; gases have more entropy than liquids, which have more than solids.

What two factors favor a spontaneous chemical reaction?

Reactions tend to be spontaneous when they release energy (decreasing enthalpy, exothermic, −ΔH) and when they increase disorder (increasing entropy, +ΔS).

According to the Arrhenius theory, what defines an acid and a base?

An Arrhenius acid produces hydrogen ions (H⁺ / H3O⁺) as the only positive ion in aqueous solution; an Arrhenius base produces hydroxide ions (OH⁻) as the only negative ion in solution.

According to the Brønsted-Lowry theory, what is an acid and a base?

A Brønsted-Lowry acid is a proton (H⁺) donor; a Brønsted-Lowry base is a proton (H⁺) acceptor.

What does the pH scale measure, and what pH values are acidic, neutral, and basic?

pH measures the hydrogen-ion concentration of a solution. pH < 7 is acidic, pH = 7 is neutral, and pH > 7 is basic. Each unit change is a tenfold change in H⁺ concentration.

What is a neutralization reaction and what are its products?

A neutralization reaction is between an acid and a base, producing a salt and water (acid + base → salt + water).

In oxidation-reduction reactions, define oxidation and reduction in terms of electrons.

Oxidation is the loss of electrons (oxidation number increases); reduction is the gain of electrons (oxidation number decreases). Remember LEO the lion says GER, or OIL RIG.

What are the oxidizing agent and reducing agent in a redox reaction?

The oxidizing agent is the species that is reduced (it gains electrons, causing oxidation of another); the reducing agent is the species that is oxidized (it loses electrons, causing reduction of another).

What is the difference between an electrolytic cell and a voltaic (galvanic) cell?

A voltaic cell uses a spontaneous redox reaction to produce electrical energy (chemical→electrical). An electrolytic cell uses an external electrical source to drive a nonspontaneous reaction (electrical→chemical).

In any electrochemical cell, at which electrode does oxidation occur and at which does reduction occur?

Oxidation always occurs at the anode; reduction always occurs at the cathode (mnemonic: AN OX, RED CAT).

What is an organic compound, and what element is always present?

An organic compound is a compound that always contains carbon (typically bonded to hydrogen); carbon's ability to form four covalent bonds allows it to make chains, rings, and many compounds.

What is the difference between a saturated and an unsaturated hydrocarbon?

A saturated hydrocarbon contains only single carbon-carbon bonds (alkanes); an unsaturated hydrocarbon contains at least one double (alkene) or triple (alkyne) carbon-carbon bond.

What is the general formula for alkanes, alkenes, and alkynes?

Alkanes: CnH2n+2 (single bonds); alkenes: CnH2n (one double bond); alkynes: CnH2n−2 (one triple bond).

What are isomers?

Compounds that have the same molecular formula but different structural arrangements of atoms, giving them different properties (e.g., butane and 2-methylpropane, both C4H10).

Identify the functional group families: -OH and -COOH.

-OH is the hydroxyl group of an alcohol; -COOH is the carboxyl group of an organic (carboxylic) acid.

What is the difference between a chemical reaction and a nuclear reaction?

Chemical reactions involve the valence electrons and rearrange atoms without changing the nucleus; nuclear reactions involve changes in the nucleus (protons/neutrons), can change one element into another, and involve far greater energy.

Compare alpha, beta, and gamma radiation in terms of charge, mass, and penetrating power.

Alpha (He nucleus, +2 charge, heavy, least penetrating, stopped by paper); beta (electron, -1 charge, light, moderate penetration, stopped by aluminum); gamma (high-energy photon, no charge, no mass, most penetrating, needs lead/concrete).

What is half-life?

The time required for half of the atoms (nuclei) in a radioactive sample to decay; it is constant for a given isotope regardless of sample size.

If a 100 g sample of a radioactive isotope has a half-life of 10 years, how much remains after 30 years?

30 years = 3 half-lives. 100 g → 50 g → 25 g → 12.5 g, so 12.5 g remains.

What is the difference between nuclear fission and nuclear fusion?

Fission is the splitting of a large nucleus into smaller nuclei (releasing energy, used in nuclear reactors); fusion is the combining of small nuclei into a larger one (releasing even more energy, as in the sun).