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Intro to Chemistry
Table of Contents
Unit 18 Overview: Representative Elements: Metals to Nonmetals
18.1 Periodicity
18.2 Occurrence and Preparation of the Representative Metals
18.3 Structure and General Properties of the Metalloids
18.4 Structure and General Properties of the Nonmetals
18.5 Occurrence, Preparation, and Compounds of Hydrogen
18.6 Occurrence, Preparation, and Properties of Carbonates
18.7 Occurrence, Preparation, and Properties of Nitrogen
18.8 Occurrence, Preparation, and Properties of Phosphorus
18.9 Occurrence, Preparation, and Compounds of Oxygen
18.10 Occurrence, Preparation, and Properties of Sulfur
18.11 Occurrence, Preparation, and Properties of Halogens
18.12 Occurrence, Preparation, and Properties of the Noble Gases

💏intro to chemistry review

18.5 Occurrence, Preparation, and Compounds of Hydrogen

Citation:

Hydrogen, the simplest element, plays a crucial role in chemistry. It's prepared through methods like steam-methane reforming and electrolysis of water. These processes yield hydrogen for various applications, from fuel cells to industrial synthesis.

Hydrogen forms diverse compounds with both metals and nonmetals. Its reactions range from combustion with oxygen to form water, to combining with nitrogen to produce ammonia. Understanding hydrogen's properties and reactions is key to grasping fundamental chemical principles.

Occurrence and Preparation of Hydrogen

Preparation and uses of hydrogen

  • Steam-methane reforming process
    • Involves reacting methane ($CH_4$) with high-temperature steam ($H_2O$) ranging from 700-1100°C in the presence of a nickel catalyst
    • Produces a mixture of hydrogen ($H_2$) and carbon monoxide ($CO$) known as synthesis gas or syngas
    • Additional hydrogen and carbon dioxide ($CO_2$) are produced by further reacting carbon monoxide with steam in the water-gas shift reaction
  • Electrolysis of water method
    • Uses electricity to split water molecules into hydrogen and oxygen gases
    • Requires a direct current (DC) power source and two electrodes: a cathode and an anode
    • Hydrogen gas is generated at the cathode, while oxygen gas is generated at the anode
  • Ammonia production via the Haber-Bosch process
    • Involves reacting hydrogen with nitrogen ($N_2$) at high temperatures and pressures using an iron catalyst
    • Ammonia is widely used in the production of fertilizers, plastics, and explosives
  • Hydrogenation of unsaturated fats and oils
    • Involves adding hydrogen to unsaturated bonds in vegetable oils to create saturated fats (margarine)
  • Methanol production
    • Involves reacting hydrogen with carbon monoxide or carbon dioxide using a catalyst
    • Methanol is commonly used as a fuel additive and solvent
  • Fuel cells
    • Convert chemical energy from hydrogen and oxygen into electrical energy
    • Used in various applications such as portable power sources and electric vehicles

Isotopes of Hydrogen

  • Hydrogen has three naturally occurring isotopes: protium, deuterium, and tritium
  • These isotopes differ in the number of neutrons in their nuclei, affecting their mass and nuclear properties
  • Deuterium and tritium are important in nuclear reactions and research

Compounds and Reactions of Hydrogen

Chemical properties of hydrogen

  • Reactions with nonmetals
    • Hydrogen reacts with halogens (F, Cl, Br, I) to form hydrogen halides (HF, HCl, HBr, HI)
      • These reactions are exothermic and produce colorless, acidic gases that dissolve in water
    • Hydrogen reacts with oxygen to form water ($H_2O$)
      • This combustion reaction releases a significant amount of energy
      • $2H_2(g) + O_2(g) \rightarrow 2H_2O(l)$
    • Hydrogen reacts with nitrogen at high temperatures and pressures to form ammonia ($NH_3$)
      • This reaction is known as the Haber-Bosch process: $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$
  • Reactions with metals
    • Hydrogen reacts with active metals (sodium, potassium) to form ionic hydrides
      • Hydrides contain the hydride ion ($H^-$) and act as strong reducing agents
      • Example reaction: $2Na(s) + H_2(g) \rightarrow 2NaH(s)$
    • Certain transition metals (palladium, platinum) can absorb hydrogen to form metal hydrides
      • Metal hydrides can store and release hydrogen, making them useful for hydrogen storage applications
  • Redox reactions
    • Hydrogen can act as both a reducing agent (losing electrons) and an oxidizing agent (gaining electrons) in various chemical reactions

Hydrogen compounds of nonmetals

  • Water ($H_2O$)
    • Exhibits a bent molecular geometry with a bond angle of approximately 104.5°
    • Strong hydrogen bonding between molecules results in high boiling point, surface tension, and specific heat capacity
    • Acts as a universal solvent due to its polarity and ability to form hydrogen bonds with solutes
  • Ammonia ($NH_3$)
    • Exhibits a trigonal pyramidal molecular geometry with a bond angle of approximately 107°
    • Polar molecule with a lone pair of electrons on the nitrogen atom
    • Forms hydrogen bonds, leading to a higher boiling point than expected based on its molar mass
    • Acts as a weak base in aqueous solution due to its ability to accept protons (proton acceptor)
  • Hydrogen halides (HF, HCl, HBr, HI)
    • Exhibit linear molecular geometry
    • Polar molecules due to the difference in electronegativity between hydrogen and the halogen
    • Form strong acids in aqueous solution (hydrofluoric acid, hydrochloric acid)
    • Acid strength increases from HF to HI due to decreasing bond strength and increasing bond length
  • Hydrocarbons (methane, ethane, propane)
    • Compounds containing only hydrogen and carbon
    • Nonpolar molecules with tetrahedral (methane), zigzag (ethane), or branched (propane) structures
    • Low boiling points and poor solubility in water due to the absence of hydrogen bonding
    • Combustible and commonly used as fuels

Bonding in Hydrogen Compounds

  • Covalent bonding is the primary type of bonding in hydrogen compounds
  • Lewis structures can be used to represent the electron arrangement in hydrogen-containing molecules, showing shared electron pairs and lone pairs
  • The role of catalysis in hydrogen reactions, such as in the steam-methane reforming process, is crucial for increasing reaction rates and efficiency

Key Terms to Review (36)

Aromatic hydrocarbons: Aromatic hydrocarbons are a class of hydrocarbons that contain one or more benzene rings in their molecular structure. They are known for their stability and unique chemical properties due to resonance.
Atwater system: The Atwater system is a method used to estimate the metabolizable energy content of foods by assigning specific caloric values to macronutrients: carbohydrates, proteins, and fats. It is widely used in nutrition science to determine the energy available from food consumption.
Anode: The anode is the electrode where oxidation occurs in a galvanic cell. It is typically the negative terminal in such cells.
Electrolysis: Electrolysis is a chemical process in which electrical energy is used to drive a non-spontaneous chemical reaction. It involves passing an electric current through an electrolyte, causing ions to move and resulting in the deposition of substances at the electrodes.
Haber process: The Haber process is an industrial method for synthesizing ammonia from nitrogen and hydrogen gases using a metal catalyst under high pressure and temperature. This ammonia is crucial for fertilizers and other chemical products.
Hydrogenation: Hydrogenation is a chemical reaction that involves the addition of hydrogen (H$_2$) to another compound, typically in the presence of a catalyst. It is commonly used to convert unsaturated fats to saturated fats and in the production of various chemicals.
Hydrogen bonding: Hydrogen bonding is a strong type of dipole-dipole interaction that occurs between molecules when hydrogen is covalently bonded to electronegative atoms like oxygen, nitrogen, or fluorine. This bond results in higher boiling and melting points for substances.
Hydrogen halides: Hydrogen halides are binary compounds formed when hydrogen reacts with halogens. They exist as diatomic molecules and are known for being strong acids when dissolved in water.
Isotopes: Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This results in different atomic masses for the isotopes of an element.
Proton: A proton is a subatomic particle found in the nucleus of an atom, carrying a positive electric charge. Protons contribute to the atomic number and define the element.
Lewis Structures: Lewis structures, also known as Lewis dot diagrams, are a visual representation of the bonding between atoms in a molecule. They depict the arrangement of atoms and the sharing or transfer of valence electrons, providing insights into the structure and properties of chemical compounds.
Hydrogen Bonding: Hydrogen bonding is a type of dipole-dipole intermolecular force that occurs when a hydrogen atom covalently bonded to a highly electronegative element, such as nitrogen, oxygen, or fluorine, experiences an attractive force with another nearby highly electronegative element. This attractive force is significantly stronger than a typical dipole-dipole interaction and has a significant impact on the physical and chemical properties of various compounds.
Hydrogen: Hydrogen is the simplest and lightest element in the periodic table, with a single proton and electron in its neutral state. It is a highly reactive nonmetal that plays a crucial role in various chemical processes and is a fundamental component of many compounds, making it a key topic across several areas of chemistry.
Proton: A proton is a subatomic particle that carries a positive electric charge and is found in the nucleus of an atom. Protons are fundamental to the structure and behavior of atoms, and they play crucial roles in various areas of chemistry, including the evolution of atomic theory, acid-base chemistry, the properties of hydrogen, and nuclear physics.
Water: Water is a colorless, odorless, and tasteless liquid that is essential for life on Earth. It is the most abundant compound on the planet and plays a vital role in various chemical and biological processes, including the topics of Early Ideas in Atomic Theory, Formula Mass and the Mole Concept, Structure and General Properties of the Nonmetals, and Occurrence, Preparation, and Compounds of Hydrogen.
Isotopes: Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons in their nuclei. This difference in the number of neutrons results in variations in the atomic mass of the isotopes, while their chemical properties remain largely the same.
Redox Reactions: Redox (reduction-oxidation) reactions are a fundamental type of chemical reaction where the transfer of electrons occurs between two or more reactants. In these reactions, one substance is oxidized (loses electrons) while another is reduced (gains electrons), maintaining the overall charge balance.
Ammonia: Ammonia is a colorless, pungent-smelling gas that is an important compound in various chemical reactions and processes. It is composed of one nitrogen atom and three hydrogen atoms, with the chemical formula NH3. Ammonia is a key player in several topics covered in this chemistry course, including the classification of chemical reactions, the structure of atoms, catalysis, buffer solutions, and the properties and reactions of nonmetals and nitrogen.
Covalent Bonding: Covalent bonding is a type of chemical bond that involves the sharing of one or more pairs of electrons between atoms. This type of bond is responsible for the formation of many stable molecules and is a fundamental concept in understanding the structure and properties of various substances, including those covered in the topics of 8.3 Multiple Bonds, 18.1 Periodicity, 18.3 Structure and General Properties of the Metalloids, 18.5 Occurrence, Preparation, and Compounds of Hydrogen, and 18.7 Occurrence, Preparation, and Properties of Nitrogen.
Catalysis: Catalysis is the process by which a substance, called a catalyst, increases the rate of a chemical reaction without being consumed or altered itself. Catalysts work by providing an alternative pathway for the reaction, lowering the activation energy required and allowing the reaction to proceed more quickly.
Haber-Bosch Process: The Haber-Bosch process is a critically important industrial chemical process that converts atmospheric nitrogen and hydrogen into ammonia. This synthetic process has revolutionized the production of fertilizers and is a cornerstone of modern agriculture and chemical manufacturing.
Hydrogenation: Hydrogenation is a chemical process that involves the addition of hydrogen gas to unsaturated organic compounds, such as alkenes and alkynes, in the presence of a catalyst. This process results in the conversion of the unsaturated compounds into their corresponding saturated compounds, which have important applications in various industries.
Anode: The anode is the electrode in an electrochemical cell where oxidation occurs, and electrons are released to flow through an external circuit. It is the negatively charged electrode that attracts positively charged ions and initiates the flow of electrons in a redox reaction.
Fuel Cells: Fuel cells are electrochemical devices that convert the chemical energy of a fuel, such as hydrogen, directly into electrical energy through a chemical reaction. They serve as an efficient and environmentally-friendly alternative to traditional power generation methods.
Electrolysis: Electrolysis is the process of using electric current to drive a non-spontaneous chemical reaction. It involves the decomposition of chemical compounds by passing an electric current through them, resulting in the separation of their constituent elements. This process is fundamental to various applications, including the production of metals, the treatment of water, and the recharging of batteries.
Hydrogen Halides: Hydrogen halides are a class of chemical compounds that consist of a hydrogen atom bonded to a halogen atom, such as fluorine, chlorine, bromine, or iodine. These compounds are important in the context of understanding the structure and general properties of nonmetals, as well as the occurrence, preparation, and compounds of hydrogen.
Steam-Methane Reforming: Steam-methane reforming is a process used to produce hydrogen gas, which is a crucial component in various industrial applications. It involves the reaction of methane, the primary constituent of natural gas, with steam at high temperatures to generate hydrogen and carbon monoxide.
Syngas: Syngas, short for synthesis gas, is a fuel gas mixture composed primarily of carbon monoxide, hydrogen, and often some carbon dioxide. It is an important intermediate in the production of a wide range of chemicals and fuels, and is closely connected to the occurrence, preparation, and compounds of hydrogen.
Ethane: Ethane is a simple alkane hydrocarbon with the chemical formula C2H6. It is a colorless, odorless, and flammable gas that is the second member of the alkane series and plays an important role in the context of the topics 'Occurrence, Preparation, and Compounds of Hydrogen' and 'Hydrocarbons'.
Water-Gas Shift Reaction: The water-gas shift reaction is a chemical reaction that converts carbon monoxide (CO) and water (H2O) into carbon dioxide (CO2) and hydrogen (H2). This reaction is an important process in the production and purification of hydrogen gas, which has applications in various industries.
Hydrocarbons: Hydrocarbons are organic compounds consisting entirely of carbon and hydrogen atoms. They are the simplest organic compounds and serve as the building blocks for more complex organic molecules. Hydrocarbons are of great importance in the context of both the occurrence and preparation of hydrogen compounds, as well as being a fundamental class of organic compounds.
Propane: Propane is a colorless, odorless, flammable gas that is a member of the alkane family of hydrocarbons. It is commonly used as a fuel for heating, cooking, and powering various appliances, and is also an important industrial chemical with numerous applications in the context of the topics 18.5 Occurrence, Preparation, and Compounds of Hydrogen and 20.1 Hydrocarbons.
Hydride Ion: The hydride ion, denoted as H⁻, is a negatively charged species consisting of a single hydrogen atom with an extra electron. It is an important concept in the context of the occurrence, preparation, and compounds of hydrogen.
Metal Hydrides: Metal hydrides are chemical compounds formed by the combination of a metal and hydrogen. These compounds have unique properties and play a significant role in the occurrence, preparation, and various applications of hydrogen as an element.
Methane: Methane is a colorless, odorless gas with the chemical formula CH₄, primarily composed of carbon and hydrogen. It is the simplest alkane and serves as a primary component of natural gas, making it an important fuel source and a significant greenhouse gas contributing to climate change.
Cathode: A cathode is an electrode where reduction occurs during an electrochemical reaction. It plays a crucial role in various processes such as galvanic cells, where it attracts cations from the electrolyte, facilitating the flow of electric current. Understanding the function of the cathode is essential for grasping concepts like electrode potentials and energy transformations in electrochemical cells.