Multiple choice: Which subatomic particle defines the atomic number of an element?
A) Neutron
B) Proton
C) Electron
D) Positron
Correct answer: B) Proton
Explanation: Atomic number equals the number of protons in the nucleus.

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Short answer: State the law of conservation of mass in a chemical reaction.
Correct answer: Mass is neither created nor destroyed during a chemical reaction; the total mass of reactants equals the total mass of products.
Explanation: Atoms are rearranged, not gained or lost.

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Fill in: Avogadro’s number is approximately ____ × 10^23 particles per mole.
Correct answer: 6.022
Explanation: One mole contains 6.022 × 10^23 entities.

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Multiple choice: Which orbital can hold a maximum of six electrons?
A) s orbital
B) p orbital
C) d orbital
D) f orbital
Correct answer: B) p orbital
Explanation: A p subshell has three orbitals, each holding two electrons.

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True or False: An endothermic process absorbs heat from the surroundings.
Correct answer: True.
Explanation: Endothermic processes have positive enthalpy change.

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Short answer: Define electronegativity.
Correct answer: Electronegativity is the tendency of an atom in a chemical bond to attract shared electrons toward itself.
Explanation: It is a relative measure of electron-attracting power.

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Multiple choice: Which bond is generally the most polar?
A) Carbon–hydrogen
B) Carbon–oxygen
C) Hydrogen–hydrogen
D) Sodium–chlorine
Correct answer: D) Sodium–chlorine
Explanation: A metal–nonmetal bond has large electronegativity difference, leading to strong polarity and ionic character.

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Fill in: The sum of all oxidation numbers in a neutral compound is ____ .
Correct answer: 0
Explanation: Charge balance requires the total to be zero.

 

Multiple choice: Which statement best describes a catalyst?
A) A substance that increases reaction rate and is consumed
B) A substance that decreases reaction rate and is not consumed
C) A substance that increases reaction rate and is regenerated
D) A substance that increases equilibrium constant
Correct answer: C) A substance that increases reaction rate and is regenerated
Explanation: Catalysts lower activation energy and are not consumed overall.

 

Short answer: State Le Châtelier’s principle.
Correct answer: When a system at equilibrium is disturbed by a change in concentration, temperature, or pressure, the system shifts to partially counteract the disturbance.
Explanation: The system responds to minimize the imposed change.

 

Multiple choice: Which gas law states that volume is directly proportional to absolute temperature at constant pressure and amount?
A) Boyle’s law
B) Charles’s law
C) Avogadro’s law
D) Dalton’s law
Correct answer: B) Charles’s law
Explanation: At constant pressure, volume ∝ temperature (kelvin).

 

Fill in: Standard temperature and pressure commonly mean a temperature of ____ kelvin and a pressure of ____ atmosphere.
Correct answer: 273.15; 1
Explanation: These are widely used standard conditions.

 

True or False: The rate constant of a reaction always increases when temperature increases.
Correct answer: True.
Explanation: Higher temperature increases the fraction of molecules with energy above the activation barrier.

 

Multiple choice: Which factor does not change the equilibrium constant for a given reaction?
A) Temperature
B) Adding a catalyst
C) Changing reaction stoichiometry representation
D) Choice of standard states
Correct answer: B) Adding a catalyst
Explanation: Catalysts affect rate, not the equilibrium position or constant.

 

Short answer: Define molarity.
Correct answer: Molarity is moles of solute per liter of solution.
Explanation: It expresses concentration based on solution volume.

 

Multiple choice: Which quantum number describes the shape of an orbital?
A) Principal quantum number (n)
B) Angular momentum quantum number (l)
C) Magnetic quantum number (m_l)
D) Spin quantum number (m_s)
Correct answer: B) Angular momentum quantum number (l)
Explanation: The angular momentum quantum number defines subshell type (s, p, d, f).

 

Fill in: A solution that resists significant change in pH upon addition of small amounts of acid or base is called a ____ .
Correct answer: buffer
Explanation: Buffers contain a weak acid and its conjugate base or vice versa.

 

True or False: Ionic solids typically have high melting points due to strong electrostatic attractions.
Correct answer: True.
Explanation: Lattice energy is large for ions with strong charges and small sizes.

 

Multiple choice: Which intermolecular force is strongest among these for neutral molecules?
A) London dispersion force
B) Dipole–dipole interaction
C) Hydrogen bonding
D) Instantaneous dipole–induced dipole
Correct answer: C) Hydrogen bonding
Explanation: It is a strong specific dipole interaction involving hydrogen bonded to highly electronegative atoms.

 

Short answer: Define standard enthalpy of formation.
Correct answer: The enthalpy change when one mole of a compound forms from its elements in their standard states at a specified temperature, typically 298.15 kelvin.
Explanation: Elements are in their most stable form under standard conditions.

 

Multiple choice: Which pair of elements is most likely to form a covalent bond?
A) Sodium and chlorine
B) Calcium and oxygen
C) Carbon and oxygen
D) Magnesium and bromine
Correct answer: C) Carbon and oxygen
Explanation: Two nonmetals usually share electrons to form covalent bonds.

 

Fill in: The number of significant figures in 0.00340 is ____ .
Correct answer: 3
Explanation: Leading zeros are not significant; trailing zero after a digit is significant.

 

True or False: In a first-order reaction, the half-life is independent of initial concentration.
Correct answer: True.
Explanation: The half-life for first-order kinetics equals ln 2 divided by the rate constant.

 

Short answer: Define the term “limiting reactant.”
Correct answer: The reactant that is completely consumed first and therefore limits the amount of product formed.
Explanation: Reaction stops when the limiting reactant is exhausted.

 

Multiple choice: Which statement about an ideal gas is correct?
A) Gas particles strongly attract each other
B) Gas particles have significant volume compared with the container
C) Gas particles move randomly and do not attract significantly
D) Gas particles lose energy during elastic collisions
Correct answer: C) Gas particles move randomly and do not attract significantly
Explanation: Ideal gas assumptions neglect intermolecular attractions and molecular volume.

 

Fill in: The mass percent of an element in a compound equals (mass of element in 1 mole of compound ÷ molar mass of compound) × ____ .
Correct answer: 100%
Explanation: Percent composition is a ratio expressed as a percentage.

 

Multiple choice: Which substance is a strong electrolyte in water?
A) Sucrose
B) Acetic acid
C) Sodium chloride
D) Ammonia
Correct answer: C) Sodium chloride
Explanation: Soluble ionic compounds dissociate completely.

 

Short answer: State Hess’s law.
Correct answer: The total enthalpy change of a reaction is the same regardless of the pathway, provided initial and final states are the same.
Explanation: Enthalpy is a state function.

 

True or False: The entropy of a perfectly crystalline substance at absolute zero kelvin is zero.
Correct answer: True.
Explanation: This is the third law of thermodynamics.

 

Multiple choice: Which molecule is nonpolar overall?
A) Water
B) Carbon dioxide
C) Ammonia
D) Hydrogen fluoride
Correct answer: B) Carbon dioxide
Explanation: The linear geometry cancels bond dipoles.

 

Fill in: The conjugate acid of ammonia is ____ .
Correct answer: ammonium
Explanation: Ammonia accepts a proton to form ammonium.

 

Short answer: Define activation energy.
Correct answer: The minimum energy that reacting particles must have to form the transition state and proceed to products.
Explanation: It is the barrier to reaction.

 

Multiple choice: Which statement about the equilibrium constant is correct?
A) It depends on initial amounts of reactants and products
B) It depends only on temperature for a given reaction
C) It always increases when a catalyst is used
D) It equals one at equilibrium
Correct answer: B) It depends only on temperature for a given reaction
Explanation: Equilibrium constant is a thermodynamic quantity determined by temperature.

 

True or False: A saturated solution contains more solute than can dissolve at a given temperature.
Correct answer: False.
Explanation: A saturated solution contains the maximum amount that can dissolve; more would remain undissolved.

 

Fill in: In a redox reaction, oxidation is the ____ of electrons and reduction is the ____ of electrons.
Correct answer: loss; gain
Explanation: “OIL RIG” is a common memory aid, but the statement defines it directly.

 

Multiple choice: Which of the following has the highest boiling point under similar conditions?
A) Methane
B) Ethane
C) Propane
D) Butane
Correct answer: D) Butane
Explanation: Greater molar mass and surface area increase dispersion forces.

 

Short answer: Define solubility.
Correct answer: The maximum amount of solute that can dissolve in a given amount of solvent at a specified temperature and pressure.
Explanation: Often expressed as grams per 100 grams solvent.

 

True or False: Bond enthalpy is always negative.
Correct answer: False.
Explanation: Breaking a bond requires energy, so bond enthalpy is positive by convention.

 

Multiple choice: What is the shape around a central atom with four bonding pairs and no lone pairs?
A) Tetrahedral
B) Trigonal planar
C) Trigonal pyramidal
D) Bent
Correct answer: A) Tetrahedral
Explanation: Four regions of electron density produce tetrahedral geometry.

 

Fill in: The process by which a liquid changes to a gas below its boiling point is called ____ .
Correct answer: evaporation
Explanation: Evaporation occurs at the surface at temperatures below boiling.

 

Multiple choice: Which solution has the highest osmotic pressure at the same temperature?
A) 0.10 molar glucose (nonelectrolyte)
B) 0.10 molar sodium chloride (assume complete dissociation)
C) 0.10 molar magnesium chloride (assume complete dissociation)
D) 0.05 molar magnesium chloride (assume complete dissociation)
Correct answer: C) 0.10 molar magnesium chloride (assume complete dissociation)
Explanation: Osmotic pressure ∝ van’t Hoff factor × molarity; magnesium chloride produces three particles.

 

Short answer: Define standard enthalpy change of reaction.
Correct answer: The enthalpy change when reactants in their standard states transform into products in their standard states at a specified temperature.
Explanation: It is calculated from formation enthalpies.

 

True or False: A spontaneous process always occurs rapidly.
Correct answer: False.
Explanation: Spontaneity is thermodynamic, not kinetic; rate can be slow.

 

Fill in: The pH of a solution is defined as the negative base-ten logarithm of the ____ ion concentration.
Correct answer: hydrogen
Explanation: pH = −log [hydrogen ion].

 

Multiple choice: Which statement about hydrogen bonding is correct?
A) It occurs only between hydrogen and carbon
B) It requires hydrogen bonded to nitrogen, oxygen, or fluorine
C) It is weaker than all other intermolecular forces
D) It requires an ionic bond
Correct answer: B) It requires hydrogen bonded to nitrogen, oxygen, or fluorine
Explanation: Strong polarity and small donor atom enable hydrogen bonds.

 

Short answer: Define lattice energy.
Correct answer: The energy released when gaseous ions combine to form one mole of an ionic solid, or the energy required to separate one mole of an ionic solid into gaseous ions.
Explanation: It measures ionic bond strength.

 

Multiple choice: Which change increases the solubility of most solid solutes in water?
A) Lowering temperature
B) Increasing temperature
C) Decreasing pressure
D) Adding a seed crystal
Correct answer: B) Increasing temperature
Explanation: Most solids dissolve more at higher temperatures.

 

True or False: The vapor pressure of a liquid increases as temperature increases.
Correct answer: True.
Explanation: More molecules have enough energy to escape the liquid.

 

Fill in: The substance that is oxidized is the ____ agent, and the substance that is reduced is the ____ agent.
Correct answer: reducing; oxidizing
Explanation: The reducing agent donates electrons; the oxidizing agent accepts electrons.

 

Multiple choice: Which pair represents an acid–base conjugate pair in the Brønsted–Lowry sense?
A) Sodium and chlorine
B) Hydrochloric acid and chloride ion
C) Water and hydrogen gas
D) Oxygen and oxide ion
Correct answer: B) Hydrochloric acid and chloride ion
Explanation: They differ by one proton.

 

Short answer: Define the term “enthalpy.”
Correct answer: Enthalpy is a state function equal to internal energy plus pressure times volume; it reflects heat flow at constant pressure.
Explanation: At constant pressure, enthalpy change equals heat absorbed or released.

 

True or False: A negative free energy change indicates that a process is spontaneous under the given conditions.
Correct answer: True.
Explanation: Negative free energy change corresponds to thermodynamic favorability.

 

Multiple choice: Which factor generally increases the rate of a reaction?
A) Lower temperature
B) Larger particle size for solids
C) Higher concentration of reactants
D) Removal of catalyst
Correct answer: C) Higher concentration of reactants
Explanation: More frequent effective collisions occur.

 

Fill in: According to the collision model, molecules must collide with sufficient energy and proper ____ to react.
Correct answer: orientation
Explanation: Proper alignment allows bonds to break and form.

 

Short answer: Define partial pressure.
Correct answer: The pressure that a gas in a mixture would exert if it alone occupied the container at the same temperature.
Explanation: It is proportional to mole fraction in ideal mixtures.

 

Multiple choice: Which statement about a buffer is correct?
A) It is made from a strong acid and its salt only
B) It is made from a strong base and its salt only
C) It is made from a weak acid and its conjugate base or a weak base and its conjugate acid
D) It must have equal volumes of acid and base
Correct answer: C) It is made from a weak acid and its conjugate base or a weak base and its conjugate acid
Explanation: Such pairs resist pH changes.

 

True or False: The energy of a photon is directly proportional to its wavelength.
Correct answer: False.
Explanation: Photon energy is inversely proportional to wavelength and directly proportional to frequency.

 

Fill in: The principal quantum number n indicates the ____ of an electron in an atom.
Correct answer: energy level (or shell)
Explanation: Higher n means higher average distance from the nucleus and higher energy.

 

Multiple choice: Which aqueous solution has the lowest freezing point, assuming ideal behavior?
A) 0.20 molar glucose
B) 0.10 molar sodium chloride
C) 0.10 molar calcium chloride (assume complete dissociation)
D) 0.20 molar urea
Correct answer: C) 0.10 molar calcium chloride (assume complete dissociation)
Explanation: The freezing point depression is proportional to particle concentration; calcium chloride yields three particles per formula unit.

 

Short answer: Define enthalpy of vaporization.
Correct answer: The heat required to convert one mole of a liquid to vapor at constant pressure and at its boiling temperature.
Explanation: It measures the strength of intermolecular forces in the liquid.

 

Multiple choice: Which statement about molecular orbital theory is correct?
A) Bonding orbitals are higher in energy than antibonding orbitals
B) Antibonding orbitals stabilize a bond
C) Bond order is proportional to the difference between electrons in bonding and antibonding orbitals divided by two
D) Bond order is always an integer
Correct answer: C) Bond order is proportional to the difference between electrons in bonding and antibonding orbitals divided by two
Explanation: Bond order = (bonding electrons − antibonding electrons) ÷ 2.

 

Fill in: The empirical formula represents the ____ whole-number ratio of atoms in a compound.
Correct answer: simplest
Explanation: It reduces subscripts to the smallest whole numbers.

 

True or False: In a galvanic cell, oxidation occurs at the anode and reduction occurs at the cathode.
Correct answer: True.
Explanation: Electrons flow from anode to cathode through the external circuit.

 

Short answer: Define standard reduction potential.
Correct answer: The potential of a reduction half-reaction measured relative to the standard hydrogen electrode under standard conditions.
Explanation: More positive values indicate greater tendency to be reduced.

 

Multiple choice: Which of the following increases the solubility of a gas in a liquid?
A) Increasing temperature
B) Decreasing pressure of the gas above the liquid
C) Increasing pressure of the gas above the liquid
D) Decreasing the polarity of the solvent
Correct answer: C) Increasing pressure of the gas above the liquid
Explanation: Henry’s law states that gas solubility is proportional to its partial pressure.

 

Fill in: The constant of proportionality in the ideal gas equation, often called the gas constant, has a value of approximately ____ liter·atmosphere per mole·kelvin.
Correct answer: 0.08206
Explanation: This value is used when pressure is in atmospheres and volume in liters.

 

True or False: The heat capacity of a substance is the amount of heat required to raise the temperature of one gram by one degree Celsius.
Correct answer: False.
Explanation: That is specific heat capacity; heat capacity refers to an object and depends on the amount.

 

Short answer: Define enthalpy of solution.
Correct answer: The heat change when a solute dissolves in a solvent to form a specified amount of solution at constant pressure.
Explanation: It can be endothermic or exothermic.

 

Multiple choice: Which is the best description of resonance in Lewis structures?
A) Atoms move rapidly among positions
B) Electrons are localized in one unique structure
C) The true structure is a hybrid of multiple valid structures differing only in electron arrangement
D) The molecule alternates between two shapes over time
Correct answer: C) The true structure is a hybrid of multiple valid structures differing only in electron arrangement
Explanation: Resonance delocalizes electrons while atom positions remain fixed.

 

Fill in: A process with negative enthalpy change and positive entropy change is ____ under all temperatures.
Correct answer: spontaneous
Explanation: Negative free energy change results from both favorable enthalpy and entropy.

 

Multiple choice: Which aqueous salt solution is expected to be acidic?
A) Sodium chloride
B) Potassium nitrate
C) Ammonium chloride
D) Sodium acetate
Correct answer: C) Ammonium chloride
Explanation: Ammonium is a weak acid conjugate; chloride is neutral.

 

Short answer: Define the term “common ion effect.”
Correct answer: The decrease in solubility or suppression of ionization of a weak electrolyte when a common ion is added from another source.
Explanation: Le Châtelier’s principle shifts equilibria.

 

True or False: Increasing ionic strength of a solution can affect activities of ions and therefore equilibrium calculations.
Correct answer: True.
Explanation: Activities differ from concentrations in nonideal solutions.

 

Fill in: The heat required to raise the temperature of one mole of a substance by one degree Celsius is called the ____ heat capacity.
Correct answer: molar
Explanation: It is specific to one mole.

 

Multiple choice: Which trend is correct across a period from left to right in the periodic table?
A) Atomic radius increases
B) Ionization energy decreases
C) Electronegativity increases
D) Metallic character increases
Correct answer: C) Electronegativity increases
Explanation: Increasing nuclear charge with similar shielding attracts electrons more strongly.

 

Short answer: Define solubility product constant.
Correct answer: The equilibrium constant for the dissolution of a sparingly soluble ionic compound, expressed in terms of the concentrations of its ions each raised to the power of its stoichiometric coefficient.
Explanation: It quantifies the extent of dissolution at equilibrium.

 

True or False: For a spontaneous endothermic dissolution, the entropy increase of the system must be significant.
Correct answer: True.
Explanation: Positive entropy can drive spontaneity even with positive enthalpy.

 

Fill in: When titrating a strong acid with a strong base, the pH at the equivalence point is approximately ____ .
Correct answer: 7
Explanation: The solution contains a neutral salt and water.

 

Multiple choice: Which statement about colligative properties is correct?
A) They depend on the identity of solute particles
B) They depend on the number of solute particles present
C) They are unaffected by electrolyte dissociation
D) They include color and viscosity
Correct answer: B) They depend on the number of solute particles present
Explanation: Examples are boiling point elevation and freezing point depression.

 

Short answer: Define enthalpy of fusion.
Correct answer: The heat required to convert one mole of a solid to a liquid at its melting temperature.
Explanation: It measures the energy needed to overcome solid-phase interactions.

 

Multiple choice: Which pair correctly matches hybridization with ideal geometry?
A) sp — trigonal planar
B) sp^2 — tetrahedral
C) sp^3 — tetrahedral
D) sp^3d — linear
Correct answer: C) sp^3 — tetrahedral
Explanation: Four electron domains give tetrahedral geometry.

 

Fill in: The tendency of a liquid to rise in a thin tube due to adhesive and cohesive forces is called ____ action.
Correct answer: capillary
Explanation: Adhesion to the tube walls and cohesion within the liquid cause a meniscus and rise.

 

True or False: The half-reaction method is used to balance oxidation–reduction equations.
Correct answer: True.
Explanation: Oxidation and reduction are balanced separately then combined.

 

Short answer: Define heat of neutralization.
Correct answer: The heat change when an acid and a base react to form one mole of water under specified conditions.
Explanation: For strong acid–strong base reactions, it is nearly constant.

 

Multiple choice: Which state function is path independent?
A) Heat
B) Work
C) Enthalpy
D) Heat plus work
Correct answer: C) Enthalpy
Explanation: Enthalpy depends only on initial and final states.

 

Fill in: The minimum amount of solute that must be added to a solvent to produce a saturated solution at a given temperature is the ____ at that temperature.
Correct answer: solubility
Explanation: It is the saturation limit.

 

True or False: In a voltaic cell, electrons flow through the salt bridge.
Correct answer: False.
Explanation: Ions move through the salt bridge; electrons move through the external circuit.

 

Short answer: Define standard state for a gas and for a solute in solution.
Correct answer: For a gas, the standard state is a pressure of one bar. For a solute, the standard state is a concentration of one mole per liter with ideal behavior.
Explanation: These conventions allow comparison of thermodynamic quantities.

 

Multiple choice: Which compound will show geometric (cis–trans) isomerism?
A) Methane
B) Ethane
C) 2-butene
D) Propane
Correct answer: C) 2-butene
Explanation: Restricted rotation around a double bond with different substituents allows geometric isomers.

 

Fill in: A solution with a hydrogen ion concentration of 1.0 × 10^−9 moles per liter has a pH of ____ .
Correct answer: 9
Explanation: pH is the negative logarithm of hydrogen ion concentration.

 

Multiple choice: Which factor most directly determines whether a reaction is product-favored at equilibrium?
A) Initial concentrations only
B) The magnitude of the equilibrium constant
C) The size of the activation energy
D) The presence of a catalyst
Correct answer: B) The magnitude of the equilibrium constant
Explanation: A large constant favors products.

 

Short answer: Define the term “enthalpy of atomization.”
Correct answer: The enthalpy change required to form gaseous atoms from the element in its standard state.
Explanation: It measures the energy to produce separated atoms.

 

True or False: An amphiprotic substance can act as both an acid and a base by donating or accepting a proton.
Correct answer: True.
Explanation: Water is a common example.

 

Fill in: The process by which a solid changes directly to a gas is called ____ .
Correct answer: sublimation
Explanation: It bypasses the liquid phase.

 

Multiple choice: Which factor does not appear in the expression for the equilibrium constant for the reaction of pure solids and pure liquids?
A) Concentration of dissolved species
B) Partial pressure of gases
C) Activities of pure solids and pure liquids
D) Temperature
Correct answer: C) Activities of pure solids and pure liquids
Explanation: Their activities are set to one, so they do not appear explicitly.

 

Short answer: Define the heat of combustion.
Correct answer: The enthalpy change when one mole of a substance is completely burned in oxygen under specified conditions.
Explanation: It measures energy released by complete oxidation.

 

True or False: A reaction with positive enthalpy change and negative entropy change can be spontaneous at high temperature.
Correct answer: False.
Explanation: Both terms oppose spontaneity at all temperatures.

 

Fill in: The slope of a plot of the natural logarithm of the rate constant versus the inverse of temperature is proportional to the negative of the ____ energy divided by the gas constant.
Correct answer: activation
Explanation: This is the Arrhenius equation in linear form.

 

Multiple choice: Which aqueous solution is expected to be basic?
A) Ammonium nitrate
B) Sodium carbonate
C) Sodium chloride
D) Potassium bromide
Correct answer: B) Sodium carbonate
Explanation: Carbonate is the conjugate base of a weak acid and will generate hydroxide ions in water.

 

Short answer: Define polarizability.
Correct answer: Polarizability is the ease with which the electron cloud of an atom or molecule can be distorted to form an instantaneous dipole.
Explanation: Greater polarizability increases dispersion forces and usually raises boiling point.