D425 Introduction to Chemistry - Set 2 - Part 1

Correct Answer: Pure substance

Option b is correct because pure substances maintain uniform properties throughout physical changes, indicating consistent molecular composition and structure.
Option a is incorrect because heterogeneous mixtures show variable properties in different regions and can be separated by physical means.
Option c is incorrect because mechanical mixtures have visibly different components that can be separated by simple physical methods.
Option d is incorrect because colloidal suspensions scatter light and show different properties when filtered or settled over time.

Correct Answer: Physical property analysis

Option b is correct because measuring melting point, density, and solubility preserves the sample while providing identifying characteristics.
Option a is incorrect because combustion destroys the sample through chemical reaction, preventing further analysis or evidence preservation needs.
Option c is incorrect because acid dissolution chemically alters the substance, making original sample recovery impossible for legal proceedings.
Option d is incorrect because electrical decomposition breaks down compounds into elements, permanently changing the chemical composition and structure.

Correct Answer: Fractional distillation

Option b is correct because fractional distillation separates liquids by boiling point differences without chemical changes to compounds.
Option a is incorrect because magnetic separation only works with ferromagnetic materials, not typical organic pharmaceutical compounds or ingredients.
Option c is incorrect because chemical precipitation involves reactions that alter substances, potentially destroying the desired pharmaceutical compound.
Option d is incorrect because gravitational settling separates by density in suspensions, not effective for dissolved pharmaceutical compounds.

Correct Answer: Electron transitions

Option b is correct because electrons jumping between energy levels emit specific light wavelengths unique to each element.
Option a is incorrect because neutron decay involves nuclear changes producing different particles, not visible light emission patterns.
Option c is incorrect because proton emission would change element identity and represents nuclear reaction, not spectral emission.
Option d is incorrect because nuclear fusion combines nuclei to form heavier elements, not the electron transitions causing spectra.

Correct Answer: Bonding strength

Option b is correct because stronger bonds between atoms create harder materials resistant to deformation or scratching.
Option a is incorrect because nuclear spin affects magnetic resonance but doesn't determine mechanical properties like hardness directly.
Option c is incorrect because radioactive decay involves nuclear instability, unrelated to mechanical hardness or material strength properties.
Option d is incorrect because magnetic moment affects magnetic properties but doesn't directly determine physical hardness of materials.

Correct Answer: Mass differences

Option b is correct because isotope mass differences affect physical processes like evaporation rates, creating measurable ratio variations.
Option a is incorrect because isotopes of the same element have identical electron configurations, producing no color differences.
Option c is incorrect because isotopes have the same proton number and electron configuration, giving identical charge properties.
Option d is incorrect because isotopes have the same electron orbitals and molecular shapes, differing only in mass.

Correct Answer: Reduction potential

Option b is correct because reduction potential differences drive electron flow from lower to higher potential spontaneously.
Option a is incorrect because color reflects light absorption properties unrelated to electron transfer tendency in electrochemical cells.
Option c is incorrect because while state affects reaction rate, electron flow direction depends on reduction potential differences.
Option d is incorrect because crystal structure affects conductivity but reduction potential determines electron flow direction and strength.

Correct Answer: Structural isomers

Option b is correct because structural isomers have identical molecular formulas but different atomic connectivity and properties.
Option a is incorrect because isotopes are atoms with same protons but different neutrons, not molecular arrangement variations.
Option c is incorrect because allotropes are different forms of the same element, not compounds with rearranged atoms.
Option d is incorrect because polymorphs are different crystal structures of the same compound, not different molecular structures.

Correct Answer: Favors fewer moles

Option b is correct because increased pressure shifts equilibrium toward the side with fewer gas molecules to reduce pressure.
Option a is incorrect because pressure effects on equilibrium follow predictable patterns based on mole differences, not random shifts.
Option c is incorrect because pressure changes affect equilibrium position when gas molecule numbers differ between reactants and products.
Option d is incorrect because pressure increase doesn't always reverse reactions; direction depends on relative mole numbers.

Correct Answer: Stoichiometric equivalence

Option b is correct because equivalence point occurs when acid and base have reacted in exact stoichiometric proportions.
Option a is incorrect because equivalence point represents precise stoichiometric relationship, not random or arbitrary ratios between reactants.
Option c is incorrect because base excess would occur past the equivalence point, not at the exact neutralization point.
Option d is incorrect because acid excess would mean incomplete neutralization, not reaching the true equivalence point yet.

Correct Answer: Dramatically increases

Option b is correct because dopant atoms provide extra electrons or holes, greatly enhancing semiconductor electrical conductivity levels.
Option a is incorrect because appropriate dopants increase rather than decrease conductivity by providing charge carriers in semiconductors.
Option c is incorrect because dopants fundamentally alter electronic properties, significantly changing conductivity from pure semiconductor values observed.
Option d is incorrect because doping enhances conductivity; it doesn't eliminate it or create perfect insulators from semiconductors.

Correct Answer: Ultraviolet radiation

Option b is correct because UV radiation provides sufficient energy to break oxygen molecular bonds initiating ozone formation.
Option a is incorrect because sound waves lack the energy needed to break chemical bonds in atmospheric oxygen molecules.
Option c is incorrect because infrared radiation causes molecular vibration and heating but insufficient energy for bond breaking.
Option d is incorrect because radio waves have even less energy than infrared, unable to initiate chemical bond breaking.

Correct Answer: Multiple interaction types

Option b is correct because proteins fold through hydrogen bonds, hydrophobic effects, disulfide bridges, and electrostatic interactions combined.
Option a is incorrect because gravitational forces are negligible at molecular scale compared to chemical and intermolecular forces present.
Option c is incorrect because proteins aren't significantly magnetic and don't align based on magnetic field interactions normally.
Option d is incorrect because sound vibrations don't determine protein structure, though ultrasound can disrupt already-formed structures.

Correct Answer: Slow cooling

Option b is correct because slow cooling allows atoms time to arrange into ordered patterns forming large crystals.
Option a is incorrect because rapid cooling traps atoms in disordered arrangements, creating small crystals or amorphous materials instead.
Option c is incorrect because constant agitation typically disrupts crystal growth rather than promoting large crystal formation processes.
Option d is incorrect because light exposure doesn't significantly affect crystal size in typical mineral formation from melts.

Correct Answer: Oxidation reactions

Option b is correct because antioxidants prevent oxygen from reacting with food molecules, stopping deterioration and rancidity development.
Option a is incorrect because crystallization is often desirable in foods like sugar and doesn't cause deterioration typically.
Option c is incorrect because melting is a physical change that doesn't cause chemical deterioration or rancidity formation.
Option d is incorrect because color changes may indicate deterioration but aren't the underlying chemical process being prevented.

Correct Answer: Half-life constant

Option b is correct because each isotope's characteristic half-life determines decay rate, independent of external conditions typically.
Option a is incorrect because radioactive decay rates are remarkably constant, unaffected by temperature changes in normal conditions.
Option c is incorrect because pressure doesn't influence nuclear decay rates, which depend on nuclear properties not external pressure.
Option d is incorrect because light exposure doesn't affect nuclear decay, though it may affect chemical reactions separately.

Correct Answer: Cross-linking degree

Option b is correct because thermoplastics have minimal cross-linking allowing remelting, while thermosets have extensive permanent cross-links.
Option a is incorrect because color additives affect appearance but don't determine whether plastics can be remelted and reshaped.
Option c is incorrect because surface texture is a physical property unrelated to the polymer's ability to remelt.
Option d is incorrect because density affects weight and strength but doesn't determine thermoplastic versus thermoset behavior directly.

Correct Answer: Carbon-hydrogen ratio

Option b is correct because combustion products directly reflect the carbon to hydrogen ratio in the original compound.
Option a is incorrect because combustion analysis gives empirical formula and ratios, not molecular mass without additional information needed.
Option c is incorrect because melting point is a physical property unrelated to combustion product ratios or analysis results.
Option d is incorrect because reaction rate depends on conditions and kinetics, not revealed by product ratio analysis.

Correct Answer: Atomic substitution

Option b is correct because different sized atoms substitute in crystal lattice, disrupting slip planes and increasing strength.
Option a is incorrect because atoms remain intact in alloys; they're rearranged in crystal structure, not destroyed or eliminated.
Option c is incorrect because alloy formation involves physical mixing of atoms, not nuclear fusion creating new elements.
Option d is incorrect because metallic bonding involves shared electrons, not removal; electrons remain in the metal structure.

Correct Answer: Moisture and oxygen

Option b is correct because water acts as electrolyte while oxygen serves as oxidizing agent in corrosion reactions.
Option a is incorrect because dry conditions slow corrosion by eliminating the electrolyte needed for electrochemical corrosion processes.
Option c is incorrect because darkness alone doesn't cause corrosion; moisture and oxygen are the critical requirement factors.
Option d is incorrect because vacuum eliminates oxygen and moisture, actually preventing rather than accelerating corrosion processes effectively.