D425 Introduction to Chemistry - Set 4 - Part 3

Correct Answer: Sulfur compounds

Option b is correct because trace hydrogen sulfide in air reacts with silver forming black silver sulfide tarnish layer.
Option a is incorrect because oxygen alone causes different oxidation; sulfur compounds specifically create the black tarnish on silver observed.
Option c is incorrect because noble gases are inert and don't react with silver; sulfur compounds cause tarnishing, not inert gases.
Option d is incorrect because water vapor alone doesn't tarnish silver; sulfur-containing compounds are the specific tarnishing agents involved chemically.

Correct Answer: Vigorous gas production

Option b is correct because acid-base reaction rapidly produces carbon dioxide foam, creating safe but impressive visual effects demonstrated.
Option a is incorrect because the reaction is safe, not explosive; it produces harmless carbon dioxide gas, not dangerous products.
Option c is incorrect because no combustion occurs; the reaction produces gas and foam, not fire or heat significantly generated.
Option d is incorrect because the products are salt, water, and gas; no metals form in this acid-base neutralization reaction.

Correct Answer: Temperature-dependent structure

Option b is correct because liquid crystal molecular arrangement changes with temperature, altering which light wavelengths are reflected visibly.
Option a is incorrect because color change is physical from structural rearrangement, not chemical reaction creating new compounds or products.
Option c is incorrect because liquid crystals aren't magnetic; temperature, not magnetism, drives the molecular rearrangement causing color changes observed.
Option d is incorrect because mood rings use thermochromic materials, not radioactive substances; temperature drives the color change safely experienced.

Correct Answer: Weak acid

Option b is correct because acids like oxalic or citric acid dissolve iron oxides while being gentle on fabric fibers.
Option a is incorrect because bases don't effectively dissolve rust and might damage fabric; acids are needed for iron oxide removal.
Option c is incorrect because water alone can't dissolve rust effectively; chemical reaction with acid is required for stain removal.
Option d is incorrect because organic solvents remove organic stains; rust is inorganic iron oxide requiring acid treatment, not solvents.

Correct Answer: Sodium azide decomposition

Option b is correct because electrical signal triggers sodium azide decomposition into nitrogen gas, rapidly inflating the airbag deployed.
Option a is incorrect because water evaporation is too slow for airbag deployment; explosive decomposition provides instant gas generation needed immediately.
Option c is incorrect because airbags use chemical gas generation, not compressed air; reaction provides the rapid expansion required effectively.
Option d is incorrect because airbags produce nitrogen, not oxygen; nitrogen is non-flammable and safe for passenger protection systems.

Correct Answer: Air and moisture

Option b is correct because oxygen, carbon dioxide, and water slowly react with copper forming protective carbonate patina layer.
Option a is incorrect because sunlight alone doesn't cause patina; chemical reaction with air and moisture creates the green layer.
Option c is incorrect because patina forms on exterior surfaces from environmental exposure, not from interior building heat rising upward.
Option d is incorrect because while biological matter might affect localized areas, atmospheric components create the uniform patina layer observed.

Correct Answer: Vinegar solution

Option b is correct because acetic acid in vinegar denatures venom proteins, neutralizing toxins and preventing further nematocyst discharge effectively.
Option a is incorrect because butter doesn't neutralize venom; it might trap toxins against skin, potentially worsening the sting reaction.
Option c is incorrect because cold doesn't denature proteins effectively; chemical neutralization with acid works better than temperature alone typically.
Option d is incorrect because salt might trigger more nematocyst firing; acid denatures proteins while salt doesn't neutralize venom chemically.

Correct Answer: Oxidation reaction

Option b is correct because bleach oxidizes colored molecules, breaking chromophore bonds that create color in stained fabric materials.
Option a is incorrect because bleach is an oxidizing agent, not reducing agent; it removes electrons from colored molecules effectively present.
Option c is incorrect because bleaching involves breaking down dissolved stain molecules, not precipitating them from solution as solids formed.
Option d is incorrect because condensation joins molecules together; bleach breaks apart colored molecules through oxidation, not joining them synthetically.

Correct Answer: Solubility difference

Option b is correct because caffeine dissolves preferentially in supercritical carbon dioxide while flavor compounds remain largely unaffected chemically.
Option a is incorrect because both caffeine and flavors are often colorless; selective extraction uses solubility, not color differences present.
Option c is incorrect because neither caffeine nor flavor compounds are magnetic; the separation uses differential solubility in extraction solvent.
Option d is incorrect because neither component is radioactive; decaffeination exploits solubility differences, not radiation properties for separation achieved successfully.

Correct Answer: Hexagonal lattice

Option b is correct because carbon atoms form perfect hexagonal honeycomb pattern providing exceptional strength and electron mobility throughout.
Option a is incorrect because graphene's properties come from its perfectly ordered structure, not random atomic arrangements or positioning present.
Option c is incorrect because graphene is a flat sheet with hexagonal pattern, not three-dimensional cubic structure like diamond crystals.
Option d is incorrect because graphene has two-dimensional hexagonal network, not one-dimensional chains; the planar structure provides unique properties.