Chemical Properties of Hydrogen for JEE

VSAT 2022


Hydrogen is the periodic table's first element. The symbol of the Hydrogen element is H. A nucleus with one unit of positive charge and one electron makes up the hydrogen atom. Hydrogen has an atomic number of 1 and a mass of 1,00797 g/mol. A colourless, odourless, and insipid gas is generated by diatomic molecules in normal circumstances known as hydrogen gas. The chemical formula of hydrogen gas is H2. Hydrogen is one of the most common chemicals in water and all organic stuff, and it is found all across the universe, not only on Earth.

Hydrogen Uses

  • The most important use of hydrogen is ammonia production. 

  • The use of hydrogen in fuel refining, such as hydrogen breaking down (hydrocracking) and sulphur removal, is rapidly expanding. 

  • The catalytic hydrogenation of unsaturated vegetable oils to generate solid fat consumes a large amount of hydrogen. 

  • Hydrogenation is utilised in the production of organic chemicals. 

  • Huge amounts of hydrogen are used as rocket fuels, in conjunction with oxygen or fluor, and as a nuclear-powered rocket propellant.

  • Internal combustion engines can consume hydrogen. 

  • Hydrogen fuel cells are being investigated as a means of generating electricity, and research is being undertaken on hydrogen as a possible key future fuel. It may, for example, be converted to and from electricity from biofuels, as well as from natural gas and diesel fuel, with no CO2 or hazardous chemical emissions.

Physical Properties of Hydrogen

  • The molecular weight of common hydrogen is 2,01594 g. 

  • It has a density of $0.071~\dfrac{g}{l}$ as a gas at 0oC and 1 atm.

  •  It has a relative density of 0.0695 when compared to air. 

  • There are three hydrogen isotopes: protium (mass 1), which makes up more than 99.985 percent of the natural element; deuterium (mass 2), which makes up about 0.015 percent of the natural element; and tritium (mass 3), which is found in small amounts in nature but can be produced artificially through various nuclear reactions. 

  • Hydrogen is the most flammable material known to man. 

  • In organic solvents, hydrogen is somewhat more soluble than in water. 

  • Several metals absorb hydrogen. Hydrogen absorption by steel can cause brittle steel, resulting in failures in chemical process equipment.

  • At room temperature, hydrogen is not a highly reactive chemical unless it has been activated in some way, such as by a suitable catalyzer. It is very reactive at high temperatures.

Chemical Properties of Hydrogen

  • Although diatomic in general, molecular hydrogen dissociates into free atoms at high temperatures. Even at room temperature, atomic hydrogen is a potent reductive agent. It interacts with various metal oxides and chlorides, including silver, copper, lead, bismuth, and mercury, to yield free metals. 

  • Some salts, such as nitrates, nitrites, and sodium and potassium cyanide, are reduced to their metallic state. It combines with a variety of elements, including metals and nonmetals, to form hydrides such as NAH, KH, H2S, and PH3. With oxygen, atomic hydrogen creates hydrogen peroxide, H2O2.

  • Despite being stable hydrogen forms compounds by combining with most elements. Hydrogen can have partial positive or negative charge depending on the electronegativity of the element it is reacting with. With electronegative elements like halogens, hydrogen acquires partial positive charge. While with electropositive elements like alkali metals, it acquires partial negative charge.

  • Atomic hydrogen combines with organic molecules to produce a complicated combination of chemicals; for example, the products of ethylene, C2H4, are ethane, C2H6, and butane, C4H10. In atomic hydrogen welding, the heat generated when hydrogen atoms recombine to create hydrogen molecules is employed to achieve high temperatures.

  • At room temperature, hydrogen interacts with oxygen to make water but when accelerated by a catalyzer, such as platinum, or an electric spark, it produces water with explosive intensity.

  • One of the special properties of hydrogen is its ability to make a type of non-covalent bonding with nitrogen, oxygen or fluorine, this bonding is named hydrogen bonding and it provides extra stability to the molecules.

  • Hydrogen can be stored by reacting it with some organic compound. For example, Hydrogen can be stored as cyclohexane by combining it with benzene, which can be dissociated into benzene and hydrogen when required.

Structure of Hydrogen

The hydrogen atom contains a nucleus that consists of a proton with one unit of positive electrical charge and an electron with one unit of negative electrical charge. Because it possesses the fewest subatomic particles of any element, hydrogen is thought to have the simplest atomic structure because of the resemblance of properties of hydrogen with both alkali metals (first group) and the halogen family (17th group), hydrogen does not have a suitable location in the periodic table.

Hydrogen's Health Consequences

It is extremely flammable. Many interactions can result in a fire or explosion. 

Exposure to high amounts of this gas can result in an oxygen-depleted atmosphere. Individuals exposed to such an environment may have symptoms such as headaches, ringing in the ears, dizziness, sleepiness, unconsciousness, nausea, vomiting, and sensory depression.

A victim's skin may turn blue in hue. Death may occur under certain conditions. Hydrogen is not believed to be carcinogenic, embryotoxic, teratogenic, or reproductively toxic.

Hydrogen's Environmental Impact

Hydrogen in the environment: Hydrogen makes up 0.15 percent of the earth's crust and is the most abundant element in water. The atmosphere contains 0.5 ppm of hydrogen H2 and various quantities of water vapour. Hydrogen is also a significant component of biomass, accounting for about 14 percent by weight. The presence of hydrogen in the atmosphere happens naturally.

Hydrogen is considered an indirect greenhouse gas, as its emission can lead to an increase in the amount of other greenhouse gases like methane which causes global warming.

FAQs on Chemical Properties of Hydrogen for JEE

1. How is hydrogen collected from water?

  • Hydrogen can be extracted from water by the process called Electrolysis of water. Water electrolysis, also known as electrochemical water splitting, is the process of utilising electricity to break down water into oxygen and hydrogen gas. 

  • This hydrogen gas can be used as hydrogen fuel or combined with oxygen to produce oxyhydrogen gas, which is utilised for welding and other purposes.

  • Water electrolysis requires a minimum potential difference of 1.23 volts, however, at that voltage, external heat from the environment is necessary.

2. What do you mean by hydrogenation and what is its purpose?

Hydrogenation is the chemical process that occurs when molecular hydrogen (H2) reacts with another substance or element, often in the presence of a catalyst such as nickel, palladium, or platinum. Organic molecules are routinely reduced or saturated using this method. The purpose of hydrogenation is to change a liquid oil into solid fat. When solid fats of the necessary consistency are prohibitively costly or unavailable, hydrogenation, often in conjunction with other procedures such as interesterification or fractionation, may provide a means of producing the needed fat.

3. What function does hydrogen play as an energy carrier?

Because there is no naturally occurring source of meaningful quantities of hydrogen, hydrogen is not an energy resource as a combustion fuel. The Sun's energy is derived from the nuclear fusion of hydrogen, which is difficult to manage on Earth. Elemental hydrogen derived from solar, biological, or electrical sources takes more energy to produce than can be acquired by burning it, hence in these instances, hydrogen acts as an energy transporter, similar to a battery. Although hydrogen may be produced from fossil fuels (such as methane), these sources are not sustainable.