Which group's metals have the largest atomic radii and the lowest first ionization energies in their periods?
Group 1
✓
Group 2
Group 13
Group 17
Correct Answer
Group 1
The alkali metals of group 1 have a single valence electron far from the nucleus, so they are the largest atoms in each period and lose that electron most easily. Group 2 atoms are smaller and hold their electrons more tightly. Group 13 atoms have a higher nuclear charge and are smaller still. Group 17 contains nonmetals with some of the highest ionization energies in each period.
Category: Representative Metals
Question 2
Because of the inert pair effect, which thallium ion is more stable than Tl3+ in aqueous solution?
Tl2+
Tl+
✓
Tl-
Tl4+
Correct Answer
Tl+
The inert pair effect makes heavy p-block elements tend to keep their pair of valence s electrons, giving a stable ion with a charge two below the group value, so thallium in group 13 forms Tl+. Tl2+ does not correspond to losing either the p electron alone or all three valence electrons. Tl- would require a metal to gain an electron. Tl4+ would require removing more electrons than thallium has in its valence shell.
Category: Representative Metals
Question 3
Aluminum metal reacts with hydrochloric acid and also with sodium hydroxide solution. Which gas is released in both reactions?
Oxygen
Chlorine
Hydrogen
✓
Nitrogen
Correct Answer
Hydrogen
Aluminum is amphoteric, and in both acid and base it is oxidized while H+ or water is reduced to hydrogen gas. Oxygen would require water to be oxidized, which aluminum cannot do. Chlorine would require chloride ions to be oxidized, but aluminum is a reducing agent. Nitrogen is not present in either reaction mixture.
Category: Metal Production
Question 4
How is aluminum metal produced commercially?
Reduction of aluminum oxide with coke in a blast furnace
Electrolysis of an aqueous aluminum chloride solution
Heating an aluminum sulfide ore in air
Electrolysis of aluminum oxide dissolved in molten cryolite
✓
Correct Answer
Electrolysis of aluminum oxide dissolved in molten cryolite
Purified aluminum oxide from bauxite is dissolved in molten cryolite, which lowers the melting temperature, and electrolysis deposits aluminum at the cathode. Reduction of aluminum oxide with coke in a blast furnace fails because aluminum is too reactive to be reduced by carbon this way. Electrolysis of an aqueous aluminum chloride solution would reduce water to hydrogen instead of producing aluminum. Heating an aluminum sulfide ore in air is not used because aluminum is not mined as a sulfide.
Category: Metal Production
Question 5
In zinc production, zinc oxide is heated with which reducing agent to release zinc vapor that is then distilled?
Carbon
✓
Oxygen
Nitrogen
Chlorine
Correct Answer
Carbon
Carbon from coal removes oxygen from zinc oxide at high temperature, and the zinc boils off and is collected by distillation. Oxygen is an oxidizing agent and is used earlier to roast sulfide ores into the oxide. Nitrogen is too unreactive to reduce a metal oxide. Chlorine is a strong oxidizing agent, not a reducing agent.
Category: Metal Production
Question 6
When magnesium is recovered from seawater, which compound is added to precipitate magnesium hydroxide?
Sodium chloride
Calcium hydroxide
✓
Hydrochloric acid
Carbon dioxide
Correct Answer
Calcium hydroxide
Adding calcium hydroxide supplies hydroxide ions that precipitate the less soluble magnesium hydroxide, which is then converted to magnesium chloride and electrolyzed in molten form. Sodium chloride is already present in seawater and supplies no hydroxide. Hydrochloric acid is used afterward to dissolve the hydroxide, not to precipitate it. Carbon dioxide forms carbonic acid, which would not precipitate a hydroxide.
Category: Metal Production
Question 7
Which element is classified as a metalloid?
Gallium
Bismuth
Germanium
✓
Phosphorus
Correct Answer
Germanium
Germanium lies along the boundary between metals and nonmetals and is a semiconductor; other elements commonly classified as metalloids include boron, silicon, arsenic, antimony and tellurium. Gallium is a group 13 metal. Bismuth is the metallic heavy member of group 15. Phosphorus is a nonmetal.
Category: Metalloids
Question 8
Boric oxide, B2O3, is a key ingredient of which heat-resistant material used for laboratory beakers and ovenware?
Stainless steel
Fused alumina
Portland cement
Borosilicate glass
✓
Correct Answer
Borosilicate glass
Adding boric oxide to silica gives borosilicate glass, which expands very little when heated and so resists cracking under sudden temperature changes. Stainless steel is an iron alloy containing chromium, not a boron compound. Fused alumina is made from aluminum oxide. Portland cement is made mainly from calcium silicates.
Category: Metalloids
Question 9
Which element is the most abundant in Earth's crust by mass?
Oxygen
✓
Silicon
Aluminum
Iron
Correct Answer
Oxygen
Oxygen makes up roughly half of the crust's mass, mostly bonded to silicon in silicate minerals. Silicon is second, at nearly one quarter of the crust. Aluminum is a major crustal element but far less abundant than these two. Iron is abundant in the core but makes up much less of the crust.
Category: Metalloids
Question 10
Why does SiO2 form a network solid while CO2 exists as discrete molecules?
Silicon atoms are smaller than carbon atoms
Silicon does not readily form double bonds with oxygen
✓
Silicon has more valence electrons than carbon
Silicon forms ionic bonds with oxide ions
Correct Answer
Silicon does not readily form double bonds with oxygen
Carbon forms strong C=O double bonds and makes small molecules, but the larger silicon atom forms only single bonds to oxygen, so each silicon bonds to four oxygens that bridge to other silicons in a network. Silicon atoms are smaller than carbon atoms is false because silicon is larger. Silicon has more valence electrons than carbon is false because both have four. Silicon forms ionic bonds with oxide ions is false because Si-O bonds are covalent.
Category: Metalloids
Question 11
Which acid is the only common acid that reacts with silicon dioxide and silicate glass?
Hydrochloric acid
Nitric acid
Hydrofluoric acid
✓
Sulfuric acid
Correct Answer
Hydrofluoric acid
Hydrofluoric acid attacks silica because the Si-F bond is even stronger than the Si-O bond, which is why it is used to etch glass. Hydrochloric acid does not react with silica and is stored in glass bottles. Nitric acid also leaves glass unchanged. Sulfuric acid is likewise stored and handled in glass.
Category: Metalloids
Question 12
Why does graphite conduct electricity?
Each of its carbon atoms is bonded to four neighbors
Weak forces hold its carbon layers together
Metal impurities lie between its carbon layers
Delocalized electrons move freely within its carbon layers
✓
Correct Answer
Delocalized electrons move freely within its carbon layers
In graphite each carbon is sp2 hybridized and bonded to three others in flat sheets, leaving pi electrons delocalized across each layer that can carry a current. Each of its carbon atoms is bonded to four neighbors describes diamond, which is an insulator. Weak forces hold its carbon layers together explains why graphite is soft and slippery, not why it conducts. Metal impurities lie between its carbon layers is not the source of graphite's conductivity.
Category: Carbon Allotropes
Question 13
What name is given to cage-shaped molecules such as C60, whose atoms are arranged like the panels of a soccer ball?
Fullerene
✓
Graphene
Nanotube
Diamond
Correct Answer
Fullerene
Fullerenes are closed cages of carbon atoms, and C60 is the best known example. Graphene is a single flat sheet of carbon one atom thick. A nanotube is a sheet of carbon rolled into a hollow tube. Diamond is a three-dimensional network solid, not a molecule.
Category: Carbon Allotropes
Question 14
Which form of phosphorus is made of discrete P4 molecules, ignites spontaneously in air, and is stored under water?
Red phosphorus
White phosphorus
✓
Black phosphorus
Phosphate rock
Correct Answer
White phosphorus
White phosphorus consists of separate P4 tetrahedra, is highly reactive and toxic, and must be kept under water to keep it from catching fire. Red phosphorus is a polymer of linked P4 units and is far less reactive. Black phosphorus is a layered network form, not a molecular solid. Phosphate rock is a calcium phosphate ore, not elemental phosphorus.
Category: Nitrogen and Phosphorus
Question 15
Why is N2 gas so unreactive?
It has an unpaired electron
It exists as single atoms
It has a very strong triple bond
✓
It is an ionic compound
Correct Answer
It has a very strong triple bond
The two nitrogen atoms in N2 share a triple bond, one of the strongest bonds known, so a great deal of energy is needed to break the molecule apart. It has an unpaired electron is false; N2 has all of its electrons paired, and unpaired electrons usually make a species more reactive. It exists as single atoms is false because nitrogen is diatomic. It is an ionic compound is false because the two identical atoms share electrons equally in a covalent bond.
Category: Nitrogen and Phosphorus
Question 16
Which nitrogen oxide is a brown gas that combines with itself to form a colorless compound at low temperature?
NO
N2O
N2O5
NO2
✓
Correct Answer
NO2
NO2 is brown, and two molecules join to form colorless N2O4 as the temperature drops. NO is a colorless gas. N2O, used as an anesthetic, is also colorless. N2O5 is a white solid rather than a brown gas.
Category: Nitrogen and Phosphorus
Question 17
When potassium burns in excess O2, it forms KO2. Which anion does this compound contain?
Superoxide
✓
Peroxide
Oxide
Hydroxide
Correct Answer
Superoxide
KO2 contains the superoxide ion, O2 with a 1- charge, which the larger alkali metals potassium, rubidium and cesium form in excess oxygen. Peroxide, O2 with a 2- charge, is the ion in Na2O2. Oxide, a single O with a 2- charge, would give the formula K2O. Hydroxide contains hydrogen, which is absent from KO2.
Category: Oxygen and Sulfur
Question 18
What does ozone in the stratosphere do that protects life on Earth's surface?
It supplies oxygen for respiration
It absorbs harmful ultraviolet radiation
✓
It removes carbon dioxide from the air
It converts nitrogen into nitrates
Correct Answer
It absorbs harmful ultraviolet radiation
Stratospheric ozone absorbs much of the sun's ultraviolet radiation before it reaches the ground. It supplies oxygen for respiration is wrong because living things breathe O2 from the lower atmosphere. It removes carbon dioxide from the air is wrong because ozone does not react with carbon dioxide. It converts nitrogen into nitrates is wrong because ozone plays no role in forming the nitrates that living things use.
Category: Oxygen and Sulfur
Question 19
Which element is mined from underground deposits by melting it with superheated water and forcing it to the surface with compressed air?
Phosphorus
Sodium
Sulfur
✓
Iodine
Correct Answer
Sulfur
The Frasch process pumps superheated water down a pipe to melt deposits of elemental sulfur, and compressed air pushes the liquid up, giving a product pure enough for most uses. Phosphorus does not occur free in nature and is made from phosphate rock. Sodium is too reactive to occur as the free metal. Iodine is obtained from iodate impurities in mineral deposits by chemical reduction.
Category: Oxygen and Sulfur
Question 20
Which halogen is a deep reddish-brown liquid at room temperature?
Chlorine
Iodine
Fluorine
Bromine
✓
Correct Answer
Bromine
Bromine is the only halogen that is a liquid under ordinary conditions, and it gives off a visible reddish vapor. Chlorine is a greenish-yellow gas. Iodine is a grayish-black solid that sublimes to a violet vapor. Fluorine is a pale yellow gas.
Category: Halogens and Noble Gases