Chemistry Regents Exam Notes

Chemistry Regents Exam Notes

General Exam Information

• The exam tests knowledge of chemistry.
• Use the provided 2011 Edition Reference Tables for Physical Setting/Chemistry.
• Answer all questions in all parts of the examination.
• Record answers to Part A and Part B–1 multiple-choice questions on the separate answer sheet.
• Record answers for the questions in Part B–2 and Part C in the separate answer booklet.
• All answers in the answer booklet should be written in pen, except for graphs and drawings, which should be done in pencil.
• A four-function or scientific calculator and a copy of the 2011 Edition Reference Tables must be available.

Part A

Subatomic Particles

• The nucleus of an oxygen atom contains protons and neutrons.

Atomic Structure

• Atoms have opposite charges and are equal in number

Wave-Mechanical Model

• In the wave-mechanical model, an orbital identifies a region in an atom of lithium that is the most probable location of electrons in the ground state.

Isotopes of Carbon

• C-12 and C-13 are isotopes of carbon because they have the same number of protons but a different number of neutrons.

Properties at STP

• At STP, the phase of each sample can be used to differentiate between a 2.0-gram sample of oxygen, $O_2(g)$, and a 2.0-gram sample of helium, $He(g)$.

Molecular Structures and Properties

• Oxygen, $O<em>2$, and ozone, $O</em>3$, have different molecular structures and different properties.

Chemical Breakdown

• Ammonia can be broken down by chemical means.

Bonding at STP

• Metallic bonding is present in a sample of zinc at STP.

Nonpolar Molecule

• $CH_4$ represents a nonpolar molecule.

Bond Formation

• Energy is released as a bond is formed. $F + F \rightarrow F_2$

Attraction for Electrons

• Based on Table S, oxygen has the greatest attraction for electrons in a chemical bond in Group 16.

Solutions

• A solution of sodium hydrogen carbonate in water is classified as a homogeneous mixture.

Proportion of Components

• In $KBr(aq)$, the proportion of its components can be varied.

Kinetic Molecular Theory

• According to the kinetic molecular theory, the particles of an ideal gas have random, constant, straight-line motion.

Chemical Reaction

• A chemical reaction is most likely to occur when reactant particles collide with the proper orientation and proper energy.

Volume and Molecules at STP

• At STP, 44 L of $O<em>2(g)$ contains the same number of molecules as 44 liters of $NO</em>2(g)$ at STP.

Exothermic Change

Based on Table I, $2C(s) + 2H<em>2(g) \rightarrow C</em>2H_4(g)$ is exothermic. Rate of Reaction

• Surface area affects the rate of a chemical reaction.

Net Energy

• The net amount of energy released or absorbed is the potential energy of the products minus the potential energy of the reactants.

Catalyst

• A catalyst increases the rate of a chemical reaction by providing an alternate reaction pathway that has a lower activation energy.

Systems in Nature

• Systems in nature tend to undergo changes toward lower energy and more disorder.

Bonding to form chains, rings, and networks

• Atoms of carbon bond with each other to form chains, rings, and networks.

Functional Group

• A molecule of 1-propanol contains an -OH functional group.

Isomers

• Butane and methylpropane are isomers of each other because they have the same molecular formula and different structures.

Multiple Covalent Bond

• Molecules of ethene and ethyne each contain a multiple covalent bond.

Organic Reaction

• Substitution identifies a type of organic reaction.

Electrochemical Cell

• Oxidation occurs at the anode, and reduction occurs at the cathode.

Reaction Products

• Neutralization yields a salt and water as the only products.

Nuclear Process

• In nuclear fission, heavy nuclei are split into lighter nuclei.

Fission Reaction

• Mass is converted to energy, explaining the large amount of heat produced during a fission reaction.

Part B-1

Approximate Mass of an Ion

• An ion with 12 protons, 13 neutrons, and 10 electrons has an approximate mass of 25 u.

Bright-Line Spectrum

• Mixture C contains element X.

Valence Electrons

• An atom with an electron configuration of 2-8-18-3 has 3 valence electrons.

Electronegativity and Atomic Radius

• As the first seven elements in Period 3 are considered in order of increasing atomic number, electronegativity increases and atomic radius decreases.

Chemical Name

• $KClO_2$ is potassium chlorite.

Percent by Mass

• The percent by mass of oxygen in $CH_3COOH$ is 53%.

Electron Sharing

• Four electrons are shared between the carbon atom and the oxygen atom in a molecule of HCHO.

Particle Arrangement

• Diagram 3 represents the arrangement of particles in a sample of neon at STP.

Significant Figures

• The mass of the copper sample is expressed to 4 significant figures.

Energy Transfer

• Thermal energy is transferred from the copper to the water.

Phase Equilibrium

• Sealing the flask with a stopper will cause the system to reach phase equilibrium.

Heat Released

• 91.8 kJ of heat are released when 1.0 mole of $NH_3(g)$ is formed from its elements at 101.3 kPa and 298 K.

Phase Change

• The phase change is endothermic and entropy increases.

Oxidation Half-Reaction

• $Mn \rightarrow Mn^{2+} + 2e^-$ represents an oxidation half-reaction.

Redox Reaction

• $C(s) + O<em>2(g) \rightarrow CO</em>2(g)$ represents a redox reaction.

Spontaneous Reaction

• Based on Table J, magnesium will react spontaneously with $Fe^{2+}(aq)$ ions.

Electrical Conductivity

• Based on Table F, a saturated solution of $NaNO_3$ is the best conductor of electricity.

Acid-Base Theory

• According to one acid-base theory, $HSO_3^-$ acts as an acid because it is an $H^+$ donor.

pH Value

• The pH value is 2.0.

Energy Source Risk

• Nuclear fission produces radioactive waste.

Part B-2

Light Emission

• Light emitted by excited boron atoms is produced when electrons lose energy and move to lower energy states.

Atomic Mass Calculation

• Numerical setup for calculating the atomic mass of copper: $(62.93 u \times 0.6915) + (64.93 u \times 0.3085)$

Percent Error

$Percent Error = |\frac{Accepted Value - Experimental Value}{Accepted Value}| \times 100$
*$Percent Error = |\frac{30.85 - 31.47}{30.85}| \times 100 = 2.01\%$

Element Classification

• Based on the location of Group 2 elements on the Periodic Table, these elements are metals.

Atomic Radius

• The atomic radius of a calcium atom is greater than that of a magnesium atom because calcium has more electron shells.

First Ionization Energy

• The general trend in first ionization energy for the Group 2 elements decreases as these elements are considered in order of increasing atomic number.

Average Kinetic Energy

• The average kinetic energy of the gas molecules in diagram 1 is equal to the average kinetic energy of the gas molecules in diagram 2 because they are at the same temperature.

Volume at STP
$\frac{P<em>1V</em>1}{T<em>1} = \frac{P</em>2V<em>2}{T</em>2}$
$\frac{60.0 kPa \times 1.8 L}{300. K} = \frac{101.3 kPa \times V<em>2}{273 K}$$V</em>2 = 0.96 L$

Pressure in Atmospheres

• $60.0 kPa \div 101.3 kPa/atm = 0.592 atm$

Potential Energy

• The potential energy of the molecules in the sample before vaporization is less than after vaporization.

Heat Required

• $q = m \times H_f$
• $q = 50.0 g \times 127 J/g$
• $q = 6350 J$

Intermolecular Forces

• The boiling point of the molecular compound is lower than the boiling point of water because it has weaker intermolecular forces than water.

Positive Ion

• The positive ion in the sample of $HCl(aq)$ solution is $H^+$.

Color of Litmus

• Based on Table M, litmus is red when placed in a sample of the original $HCl(aq)$ solution.

Concentration of HCl

• $M<em>A V</em>A = M<em>B V</em>B$
• $M_A \times 15.0 mL = 0.010 M \times 30.0 mL$
• $M_A = 0.020 M$

Part C

Bonding Types

• The two types of bonding in the compound used to make plaster casts are ionic and covalent bonding.

Noble Gas Configuration

• Neon has atoms in the ground state with the same electron configuration as the positive ion in $Mg(OH)_2$ in the ground state.

Electronegativity Difference

• Based on Table S, the electronegativity difference for the bond between zinc and oxygen in ZnO is 1.9.

Freezing Point

• The freezing point of water at standard pressure is higher than the freezing point of the $KNO_3(aq)$ solution at standard pressure.

Saturation Classification

• Based on Table G, the $KNO_3$ solution made by the student is unsaturated.

Separation Procedure

• The student can evaporate the water from the $KNO<em>3(aq)$ solution to separate the original $KNO</em>3$.

Synthesis Reaction

• Equation 1 represents a synthesis reaction because two reactants combine to form a single product.

Equilibrium System

• At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction in the equilibrium system represented by equation 2.

Hydrogen Atoms

• A molecule of hexane has 14 hydrogen atoms.

Hydrocarbon

• Octane is a saturated hydrocarbon because it contains only single carbon-carbon bonds.

Energy and the Cell

• The power source is required for the cell to operate because the reaction is nonspontaneous and requires energy input.

Moles of Electrons

• 4. 0 moles of electrons are lost when 4.0 moles of electrons are gained in this reaction.

Oxidation State

• The change in oxidation state for chlorine in this cell is -1 to 0.

Half-Life

• Using the graph, the half-life of Th-230 is $8.0 \times 10^4$ years.

Unchanged Sample

• The fraction of the Th-230 sample that remains unchanged after two half-lives is 1/4.

Penetrating Power

• The beta particle has greater penetrating power than the alpha decay particle from a Th-230 atom.

Nuclear Equation

$^{238}<em>{92}U \rightarrow ^{234}</em>{90}Th + ^4_2He$

Transmutation

• The nuclear decay of U-234 to Th-230 is considered a transmutation because the number of protons in the nucleus changes, resulting in the formation of a new element.