T3 OXYGEN Flashcards
Why does oxygen have a strong tendency to have an oxidation state of –2?
Oxygen tends to have an oxidation state of –2 because it is two electrons short of achieving a closed-shell configuration.
What distinguishes oxygen’s oxidizing power from other group 16 elements?
Only oxygen forms doubly-bonded O2 molecules, giving it strong oxidizing power compared to other elements in the group.
How do ionization energies vary within group 16 elements?
Ionization energies decrease down group 16 due to the increase in atomic radius.
What trend do electronegativities follow within group 16?
Electronegativities are high and decrease down group 16, with oxygen being the second most electronegative element.
How does larger size affect polarizability and interactions?
Larger size leads to higher polarizability, resulting in an increase in dispersion interactions.
What happens to electron affinities as you descend group 16?
Electron affinities are high and decrease down the group, except for oxygen due to increased interelectronic repulsions.
Why does the oxidizing power decrease down group 16?
The decrease in electron affinity and hydrogen leads to a decrease in oxidizing power down the group.
How does oxygen’s natural occurrence differ from other chalcogens?
Oxygen is unique as the only gas among chalcogens, forming diatomic O2 molecules, unlike other elements which prefer single bonds.
What causes the unique behavior of O2 molecules?
Various factors contribute, including higher oxidation power, negative total electron affinity, and the ability to form double bonds due to lower atomic size.
Why does oxygen form ionic metal oxides while other chalcogens form covalent compounds?
Oxygen’s low polarizability and small size lead to its ability to form ionic metal oxides, unlike sulfides, selenides, and tellurides with a strong covalent character.
What percentage of Earth’s atmosphere does oxygen make up?
Oxygen makes up about 21% of Earth’s atmosphere, primarily originating from photosynthesis.
How can oxygen be obtained in the laboratory?
Oxygen can be obtained by thermal decomposition of KClO3 or catalyzed decomposition of hydrogen peroxide in the lab.
What is the industrial method for obtaining oxygen?
Oxygen is obtained industrially by fractional distillation of liquid air, based on the difference in boiling points of N2 and O2.
What is the most stable oxidation state of oxygen?
The most stable oxidation state of oxygen is –2.
How does pH affect the oxidizing power of O2 and H2O2?
The oxidizing power of both O2 and H2O2 decreases as pH is increased.
Why is peroxide unstable in both basic and acidic conditions?
Peroxide (O.S. = –1) is unstable due to disputes in both basic and acidic conditions.
What types of bonds can oxygen form?
Oxygen can typically form two single bonds or one double bond and can act as a Lewis base to form coordinate covalent bonds.
Provide an example of oxygen forming three equivalent covalent bonds.
[H3O]+ and [O(HgCl)3]+ are examples where oxygen forms three equivalent covalent bonds.
Colors of the group 16?
O - Blue pale gass
S - Yellow solid
Se - Red solid
Te - Brown solid
What is the physical state of oxygen below 90 K?
Below 90 K, oxygen condenses to a pale blue liquid.
How it increase the size in the group?
down
How it increase the ionization energy and electronegativity in the group?
up
How it increase the MP and BP in the group?
down
What property characterizes O2?
O2 is paramagnetic.
What are the two allotropes of oxygen?
Oxygen exists as O2 (dioxygen) and O3 (ozone).
How can different polymorphs of solid oxygen be achieved?
By increasing pressure, different polymorphs of solid oxygen can be achieved. At pressures > 10 GPa, a red solid containing molecules of the third most important allotrope of oxygen, O8, exists.
How is O2’s paramagnetism explained?
Molecular orbital (MO) theory explains O2’s paramagnetism due to its unpaired electrons. The bond order (8-4)/2 = 2 in O2 and its charged species [O2]+, [O2]–, and [O2]2– are also explained by MO theory.
What distinguishes the 1g state of O2?
The 1g state has a long lifetime and is much more reactive than triplet O2. It exhibits electrophilic character as it possesses an empty π* orbital.
What electron configuration corresponds to the most stable state of O2?
The 3Sg – state corresponds to the most stable electron configuration according to Hund’s rule.
What are the major applications of O2?
O2 is used in metallurgy, steel production, synthesis of HNO3 from NH3, medical oxygen therapy, and respiratory purposes for astronauts and divers.
How is ozone (O3) produced?
O3 is produced by passing a stream of O2 through a 10- to 20-kV electric field.
What is the bond order of O3?
The bond order of O3 is 3/2, with each O–O bond being equivalent.
What is the molecular structure of O3?
O3 has an angular shape with diamagnetic properties. It exhibits two resonance forms in its Lewis structure.
What are the applications of O3 due to its high oxidizing power?
O3 is used for water purification, eliminating microbes and pathogens in various environments. However, its commercial applications are doubted due to toxicity concerns.
How is ozone formed in the stratosphere?
Ozone is formed in the stratosphere by photolysis of O2 with UV-B and UV-C radiation, following the Chapman cycle.
What is the Chapman cycle?
The Chapman cycle describes the mechanism of O3 formation and decomposition, maintaining constant O3 and O2 concentrations and absorbing UV radiation.
How do reactive chlorine atoms contribute to ozone depletion?
Reactive chlorine atoms catalyze the decomposition of O3 into O2, leading to ozone depletion. Each chlorine atom can destroy up to 50,000 O3 molecules before being quenched.
What causes ozone depletion?
Chlorofluorocarbons (CFCs) and similar substances used in refrigeration systems are responsible for ozone depletion. They generate reactive chlorine atoms in the stratosphere, which catalyze the decomposition of O3.
What is the role of ozone in the atmosphere?
Ozone absorbs life-threatening UV radiation in the atmosphere, protecting life on Earth.
What factors contribute to the formation of the ozone hole?
Factors such as the presence of UV-C and UV-B radiation, low O2 concentration above 25-30 km, and the presence of reactive chlorine atoms contribute to the formation of the ozone hole.
What is the bond length of O3 compared to O2 and H2O2?
The bond length of O3 lies between that of O2 (121 pm) and H2O2.
What is the ozonide anion, and how is it formed?
Adding 1 e– to O3 forms the ozonide anion, O3–, with a total bond order of 5/2. This increases the O–O distance compared to O3.
How does ozone’s high oxidizing power contribute to its applications?
Ozone’s high oxidizing power allows it to effectively purify water and eliminate microbes and pathogens, making it valuable for various applications. However, concerns about its toxicity limit its commercial use.
What are oxides?
Oxides are binary compounds of oxygen, except with fluorine, which is called fluoride.
What are ionic oxides, and what structures do they have?
Ionic oxides, formed with metals, have 3D structures with high melting and boiling points. Examples include antifluorite structures with alkali metals (M+), and NaCl structures with M2+.
What are covalent oxides, and what are their properties?
Covalent oxides, formed with light non-metals and metals with high oxidation states, are volatile molecular compounds. Examples include molecular oxides of non-metals (C, N, P, S) with non-extended structures and low melting and boiling points.
What are low-dimensional oxides, and why do they form?
Low-dimensional oxides, formed with heavy non-metals, have structures such as chains and planes. They form due to the presence of the inert pair, which is stereochemically active.
What are some examples of high-valent molecular oxides?
Examples include Mn2O7, Tc2O7, RuO4, OsO4, and XeO4, which are important in oxidation reactions in organic chemistry but are toxic due to their volatility.
How do oxides exhibit acid-base reactivity?
Oxides can be acidic, basic, or amphoteric depending on their behavior towards acids and bases.
How is the amphoteric character observed in oxides?
Amphoteric character is observed in oxides like BeO and those of some elements of groups 13 and 14, which lie at the frontier between acidic and basic oxides.
What characterizes the covalent oxides of non-metals?
Covalent oxides of non-metals in low oxidation states are neutral (e.g., N2O), while in high oxidation states, they are acidic
What factors determine the acidic/basic character of transition metal oxides?
In transition metals, the acidic/basic character depends on the oxidation state: low oxidation states give rise to basic oxides, intermediate states to amphoteric oxides, and high oxidation states to acidic oxides.
How does the structure of water contribute to its properties?
The tetrahedral arrangement of water molecules and hydrogen bonding lead to properties like high surface tension, melting and boiling points, capillarity force, specific heat, and heat of vaporization.
What are the properties of water?
Water is an odorless, tasteless liquid with a pale blue color. It has an angular molecular structure, strong hydrogen bonding, and high heat capacity.
What is the significance of water’s hydrogen bonds?
Hydrogen bonds in water contribute to its large surface tension, high melting and boiling points, capillarity force, specific heat, and heat of vaporization.
What is water’s role as a solvent?
Water is a good solvent due to its polarity, making it miscible with many substances and facilitating chemical reactions.
How does water regulate Earth’s weather?
Water’s high heat capacity and heat of vaporization allow it to regulate Earth’s weather by absorbing temperature fluctuations.
What is unique about water’s density?
Water reaches its maximum density at 3.98°C and expands upon freezing, explaining why ice floats on water.
How does water react with certain elements?
Elements more electropositive than hydrogen (e.g., Li, Na, K) displace hydrogen from water to form hydroxides in a violent reaction.
How is water formed and decomposed?
Water is formed by the direct reaction between hydrogen and oxygen or by the electrolysis of water. It decomposes into oxygen and hydrogen by electrolysis.
What is the domain structure of water?
The domain structure of water is tetrahedral, with an H–O–H angle of 104.5° and an H–O distance of 95.84 pm.
Why is water transparent to UV-Vis radiation but not to IR radiation?
Water’s O–H bonds absorb in the IR region, making water vapor a significant greenhouse gas.
What is the role of water in biological systems?
Water is essential for life, serving as a solvent for biochemical reactions and providing structural support to cells.
What is the structure of pure hydrogen peroxide?
Pure hydrogen peroxide (H2O2) is a viscous bluish liquid with an angular non-planar structure.
Why is hydrogen peroxide unstable against distmutation in acidic and basic media?
Hydrogen peroxide is unstable due to dismutation reactions, which are slow but can be catalyzed by various substances.
Why does hydrogen peroxide have a non-planar structure?
Hydrogen peroxide’s non-planarity minimizes electrostatic repulsion between lone pairs of oxygen atoms and hinders molecule rotation around the O–O bond.
How is the stability of hydrogen peroxide maintained in commercial solutions?
Commercial solutions of hydrogen peroxide are diluted (up to 30%) and stored in opaque bottles in the fridge to avoid decomposition accelerated by light.
What substances can catalyze the dismutation of hydrogen peroxide?
Substances with redox pairs having reduction potentials between 1.76 V (reduction of H2O2 to H2O) and 0.69 V (reduction of O2 to H2O2) can catalyze hydrogen peroxide dismutation.
How is hydrogen peroxide produced industrially?
Industrial production of hydrogen peroxide involves organic reactions with anthraquinone derivatives, followed by spontaneous oxidation in air.
What are the main uses of hydrogen peroxide?
Hydrogen peroxide is used as a bleaching agent in the paper industry, cleaning old paints, disinfectants, hair bleaching, wastewater treatment, and rocket propellants.
What are some applications of hydrogen peroxide in analytical chemistry?
Hydrogen peroxide is used to identify chromate ions by forming deep blue Cr(VI) oxide peroxide species.
How does hydrogen peroxide contribute to waste-water treatment?
Hydrogen peroxide is used in waste-water treatment as an oxidant to degrade organic pollutants.
What is the significance of hydrogen peroxide’s role in the paper industry?
Hydrogen peroxide is used as a bleaching agent in the paper industry to remove lignin and other impurities from wood pulp.
What is hydrogen peroxide’s role in rocket propulsion?
Concentrated hydrogen peroxide is used as a propellant in rockets, either alone or in combination with fuels, due to its ability to decompose and produce oxygen.
Describe the oxygen transport mechanism in vertebrates.
Oxygen is transported by hemoglobin in red blood cells, which binds to oxygen in the lungs and releases it to tissues. Myoglobin stores oxygen in muscles.
Why is hydrogen peroxide handled with care?
Hydrogen peroxide is corrosive and can cause skin and eye irritation, even when diluted, requiring proper protective measures during handling.
How is oxygen involved in biological processes?
Oxygen is essential for life, found in biomolecules like carbohydrates, fatty acids, proteins, and nucleic acids, and is involved in photosynthesis and cellular respiration.
What role does manganese play in photosynthesis?
Manganese in photosynthesis forms the active site of the oxygen evolving complex (OEC), which oxidizes water to produce dioxygen.
How does hemoglobin bind oxygen?
Hemoglobin binds oxygen to its iron-containing heme groups, inducing conformational changes that increase its affinity for subsequent oxygen molecules.
What is cooperative binding in hemoglobin?
Cooperative binding in hemoglobin occurs when the binding of one oxygen molecule increases the affinity for subsequent molecules, facilitating oxygen transport.
What are the structural differences between myoglobin and hemoglobin?
Myoglobin is a monomer found in muscles, while hemoglobin is a tetramer found in red blood cells, but both contain iron-containing heme groups.
How does oxygen binding affect the color of hemoglobin?
Oxygen binding to hemoglobin oxidizes iron from Fe2+ to Fe3+, changing its color from bluish red to bright red.
What role does oxygen play in aerobic respiration?
In aerobic respiration, glucose reacts with oxygen to produce carbon dioxide, water, and energy stored as ATP molecules.
