Hydrogen and its Properties Quiz

Hydrogen and its Compounds

• Hydrogen is element number 1 (H) on the periodic table, with an atomic mass of 1.00794.
• The name "hydrogenium" means "water-forming" (A. Lavoisier).
• Hydrogen was discovered in 1766 by Henry Cavendish.
• Hydrogen liquefied in 1883 by Olszewski and Wróblewski.
• Hydrogen liquefied in 1898 by the expansion method by Dewar.

Hydrogen in the Universe

• Hydrogen (7500) makes up a significantly larger proportion of the universe than any other element.
• 74% of the universe is hydrogen.
• 25% of the universe is helium.

Hydrogen in the Human Body

• A living cell comprises six elements: C, H, O, N, P, S.
• These organogenic elements constitute about 97.9% of the human body's mass.
• Oxygen (65%) is the most abundant element in the human body.
• Carbon (18%) is the second most abundant element in the human body.
• Hydrogen (9.5%) is the third most abundant element in the human body.

Physical Properties of Hydrogen

• Colorless, odorless, tasteless gas.
• Approximately 14 times lighter than air.
• Very slightly soluble in water.
• Soluble in some metals (e.g., palladium and platinum).
• Melting point: 13.66 K
• Boiling point: 20.13 K
• Enthalpy of vaporization: 0.904 kJ/mol-1
• Enthalpy of fusion: 0.117 kJ/mol-1
• Density (273 K): 0.090 g/dm-3
• Bond dissociation enthalpy: 435.99 kJ/mol-1
• Interatomic distance: 74.14 pm
• Standard entropy (298 K): 130.7 J/K mol-1

Ortho- and para-Hydrogen

• Hydrogen exists in ortho and para varieties, distinguished by the direction of the nuclear spin.
• Under normal conditions, hydrogen is about 75% ortho and 25% para.
• As it cools, the proportion of para-hydrogen increases.
• At 20 K, the para-hydrogen content reaches 99.7%.

Atomic Hydrogen

• Atomic hydrogen exists for a very short time at room temperature.
• It rapidly recombines.
• It reacts with chlorine, bromine, iodine, oxygen, sulfur, arsenic, and antimony to form hydrides.
• It reduces silver nitrate (V) to silver, chromates (VI) to chromium (III) salts, and potassium manganate (VII) to manganese (II) salts.

Active Hydrogen

• Active hydrogen refers to the state of hydrogen formed in a reaction, such as zinc with hydrochloric acid.
• This nascent hydrogen has highly reactive chemical properties like atomic hydrogen.
• Active hydrogen reduces KMnO4.

Isotopes of Hydrogen

• Protium (1H): 99.985% abundant light hydrogen.
• Deuterium (2H, or D): 0.0156% abundant heavy hydrogen.
• Tritium (3H, or T): Trace amounts, superheavy and radiohydrogen.

Water and Heavy Water

• Difference in boiling points between water and heavy water indicates stronger hydrogen bonding in heavy water.
• Deuterated compounds are used in solvents for NMR spectroscopy.
• Heavy water (D2O) is a moderator in nuclear reactions, reducing neutron energies.

Methods of Producing Hydrogen

• Steam reforming of natural gas is the primary method (approximately 95%).
• Partial oxidation of methane.
• Coal gasification.
• Water electrolysis.
• Hydrogen production from biomass.
• Biological methods (fermentation, biophotocatalysis).

Obtaining Water Gas

• Water gas (a mixture of hydrogen and carbon monoxide) is produced from steam and powdered coal or coke at around 1000°C in a fluidized reactor.

Obtaining Hydrogen from Water Gas

• Stage 1: Catalytic conversion of carbon monoxide in water gas and water vapor at 200-300°C.
• Stage 2: Elution of carbon dioxide under pressure using a hot potassium carbonate solution.
• Stage 3: Final purification of residual CO and other gases.

Steam-Methane Reforming

• Steam-methane reforming produces hydrogen from natural gas.
• The reaction emits a considerable amount of CO2.

Hydrogen Sources

• Sources include renewable electricity (solar, wind, hydropower) to split water.
• Most hydrogen is currently produced from natural gas.

Water Electrolysis

• Water electrolysis uses electricity to split water into hydrogen and oxygen.
• Addition of a small amount of acid, base, or salt increases conductivity.
• Electrical potential (voltage) required is about 1.229 V.

Hydrogen Production - Laboratory Methods (from acids)

• Active metals (e.g., zinc) react with dilute hydrochloric or sulfuric acids to produce hydrogen gas.

Hydrogen Production - Laboratory Methods (from water)

• Active metals (e.g., potassium, calcium) react with water to generate hydrogen gas.

Hydrogen Production - Laboratory Methods (from metal hydrides)

• Metal hydrides (e.g., lithium hydride, calcium hydride) react with water to release hydrogen gas.

Hydrogen Production - Laboratory Methods (from amphoteric metals)

• Amphoteric metals (e.g., aluminum) react with bases (e.g., sodium hydroxide) and water to produce hydrogen.

Advantages of Hydrogen as an Energy Source

• Environmentally friendly technology.
• Minimizes toxin emission into the natural environment.
• Various methods allow for large-scale hydrogen production.

Hydrogen-Air Fuel Cell

• A fuel cell where hydrogen and oxygen react electrochemically to produce electricity.

Targeted Sectors for Expanded Clean Hydrogen Use

• Hydrogen can be used in several sectors like transportation, the production of synthetic fuels, ammonia, and fertilizers.

Use of Hydrogen

• Hydrogen is used in margarine production, rocket fuels, and the production of hydrochloric acid.
• Many industrial applications involve hydrogen for processes in the chemical, petrochemical, and steel industries.
• It's used in welding torches.
• It is used in production of synthetic ammonia for the manufacture of fertilizers.

Airships

• Hydrogen's low density led to its use in airships (e.g., the Hindenburg).
• The Hindenburg's catastrophic fire in 1937 damaged public perception of airships.
• Airships are now used for tourist flights and advertising.

The Position of Hydrogen in the Periodic Table

• Hydrogen exhibits similarities to alkali metals (group 1) due to having one electron in its valence shell.
• Hydrogen also has similarities to halogens (group 17) as it can gain an electron to fill its valence shell.
• Hydrogen's electronic configuration and properties cause its placement in the periodic table to be uncertain, as it can behave both like a metal and a nonmetal.

Hydrogen Properties

• Exhibits unique chemical behaviors due to its single electron.
• Can lose or gain an electron or form single covalent bonds.

Chemical Properties of Hydrogen

• Stable at normal temperatures, but flammable in air and in the presence of gaseous chlorine.
• Reacts with chlorine, forming hydrochloric acid.
• Reacts with oxygen to produce water, often with a pale blue flame.
• Mixtures with air, oxygen, and chlorine are explosive.

Chemical Properties of Hydrogen (Continued)

• Reacts with oxygen without a catalyst at a high temperature (600°C).
• Reacts with other nonmetals at elevated temperatures.
• Reacts with alkali metals at elevated temperatures forming hydrides.

Hydrides (Naming and Production)

• Hydrides are binary compounds with hydrogen, with various categories and properties.
• Naming follows a consistent convention (e.g., sodium hydride).
• Production can involve direct synthesis from an element with hydrogen (example, H2 + S to produce H2S).
• Some are prepared through exchange reactions between hydrogen and other compounds.

Division of Hydrides

• Hydrides are categorized by their behavior towards water, acids, and bases.
• Classified as basic, neutral, or acidic, depending on the compound and the reactivity involved.
• Further divided by the nature of the chemical bond involved, such as ionic, covalent, or metallic.

Acidic Hydrides

• Hydrides of elements in groups 16 and 17 are acidic, dissolving in water to form oxygen-free acids.
• Form salts when reacted with metal hydroxides.

Basic Hydrides

• Alkali metal hydrides (e.g., sodium hydride) react with water to produce hydroxide and hydrogen gas.

Neutral Hydrides

• Neutral hydrides (e.g., methane, silicon hydride) generally don't react strongly with water or basic solutions.

Division of Hydrides (Polarity)

• Based on the partial charge of the hydrogen atom.
• Compounds with hydrogen having a larger partial positive charge (acids), and those having a partial negative charge (basic).
• Some hydrides exhibit behavior characteristic of both acidic and basic properties.

Division of Hydrides (Bond Nature)

• Salt-type hydrides (ionic).
• Covalent hydrides (molecular).
• Metallic hydrides (interstitial).

Binary Compounds of Hydrogen

• Compounds involving hydrogen and other elements, categorized by various types of bonds.

Hydrogen Bonding

• Hydrogen forms bonds with strongly electronegative atoms (N, O, F).
• Characterized as partial electrostatic and partial covalent bonds.
• Influences properties of many compounds, including water.
• Effects include reduced vapor pressure, increased boiling point, increased viscosity, a lower density in ice compared to liquid water and the dissolution of compounds.

Hydrogen Bonding Phenomena

• Open structures of water and ice, DNA's double helix, and the alpha-helices of some proteins.

Hydrogen Bonds in Biological Macromolecules

• Hydrogen bonds are essential in forming specific shapes for complex biological molecules (proteins, DNA).

Hydrogen Bonding Affects

• Hydrogen bonding impacts the properties of water and other molecules, including vapor pressure, boiling point, viscosity, and solubility.

Influence of Hydrogen Bonds

• Hydrogen bonds affect the melting point and boiling points of compounds containing them.
• Compounds with stronger hydrogen bonding show higher boiling points.

Hydrogen Bonds in Alcohols and Phenols

• Hydrogen bonds affect the properties of alcohols and phenols.