NEET Study Notes for Hydrogen - Hydrogen is one of the most essential elements in the universe and is found in large quantities but it is rarely found in a free state. Hydrogen is mostly found when it is bonded with other elements, in the form of chemical compounds. Some of the important topics from this unit include isotopes, hydrogen peroxide, physical and chemical properties of water.

• Hydrogen is the most abundant element in present in our universe. The most common form in which Hydrogen is present is in the form of a colorless, odorless, and flammable gas. Hydrogen is the lightest of all elements with an atomic weight of 1.008. The atomic number of Hydrogen is 1. 
• The three sections in NEET Chemistry Syllabus are Inorganic Chemistry, Organic Chemistry, and Physical Chemistry. Hydrogen is a part of Inorganic chemistry. The overall weightage of questions from Inorganic Chemistry is 34%.
• As per the previous year’s analysis, NEET Question Paper will comprise at least one question from Hydrogen. Candidates can start their preparation for NEET 2022 by understanding the topics explained in this article and solving the sample questions provided. 

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NEET Study Notes: Important Topics in Hydrogen

NEET Study Notes for Hydrogen

Hydrogen is the lightest and the most abundant element present in the universe. Hydrogen is rarely found in a free state in nature. Hydrogen, when burned, reacts with oxygen in the atmosphere to form water.

Hydrogen is composed of three isotopes. The three isotopes of Hydrogen are:

• 1H Protium - Protium, It has zero neutrons
• 2H-Deuterium- it has one neutron, Electrolysis of heavy water- D2O yields deuterium. Deuterium is known as heavy hydrogen
• 3H- Tritium, it has two neutrons, originates from nuclear reactions Tritium is formed in the upper atmosphere and -radioactive

Elemental deuterium and tritium have low vapor pressure in comparison to ordinary hydrogen. Due to this when liquid hydrogen evaporates, heavier isotopes concentrate in the last portions to evaporate.

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Physical properties of Hydrogen

• Hydrogen is a colorless, odorless, tasteless, neutral gas.
• Hydrogen is highly inflammable and burns with a blue flame.
• Hydrogen is less soluble in water
• Hydrogen has very low boiling points.

Chemical Properties of Hydrogen

The chemical properties of Hydrogen are:

• Due to the strong bond of enthalpy of H-H bond, Dihydrogen is relatively inert at room temperature.
• Under a high electric arc, atomic hydrogen is produced.
• With a single electron, Hydrogen orbit is incomplete.
• Hydrogen combines with almost every element

Reaction with Non- Metals

Reaction with Metals

Metals like Fe, Ni and Pd form interstitial or metallic hydrides.

Reducing Property

Hydrogenation

Also Read:

• NEET Study Notes for Reaction Mechanism

• NEET Study Notes for Chemical Equilibrium

Uses of Hydrogen

• Hydrogen is used in the preparation of Ammonia

• Hydrogen is also used as a fuel in preparation of fuel gases like water gas
• Hydrogen is used as a reducing agent in metallurgy.
• Manufacture of methyl alcohol

• Manufacture of ammonia

• Manufacture of vegetable ghee- By hydrogenation of oils in the presence of Nickle catalyst, forms vegetable ghee.
• Produce Low temperature- Hydrogen is used as cryogenic fluid.
• Balloons- Hydrogen mixed with Helium is used for filling balloons.

Forms of Hydrogen

• Atomic Hydrogen- When molecular hydrogen is passed through an electric arc (2273k) that is struck between tungsten and electrodes. This reaction is endothermic and its half life period is 0.33 seconds. Heat is stored up in atoms.

• Nascent Hydrogen- This form of Hydrogen is when it has just been formed, Nascent Hydrogen is more reactive than original hydrogen. This hydrogen is however a more powerful reducing agent than ordinary hydrogen. The reason for Nascent Hydrogen formation is atomic state ( as atoms are more reactive than molecules), Chemical energy is liberated during reaction, High internal pressure due to nascent hydrogen atoms

• Occluded Hydrogen - Hydrogen which is absorbed by certain metals like Platinum, Palladium, Iron, Nickel is known as occluded Hydrogen.

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NEET Study Notes for Hydrogen Peroxide

Hydrogen Peroxide or H2O2 is the simplest peroxide with an oxygen-oxygen single bond. It is a colorless liquid and acidic in nature. Concentrated Hydrogen Peroxide is very reactive in nature and used as a propellant in rocketry.

• Hydrogen Peroxide is a colorless liquid.
• Used in aqueous solution.
• Used as a bleaching agent and also acts as a disinfectant.
• Is a 100% degradable compound.

Preparation of Hydrogen Peroxide

• Lab Method- On acidifying barium peroxide, excess water is removed by the process of evaporation under reduced pressure and hydrogen peroxide is obtained. The reaction is

• Industrial Method- Hydrogen peroxide can also be prepared by electrolysis of ice-cold H2SO4 (30%). Peroxodisuplhate is obtained when acidified sulfaet solution is electrolyzed at high density. Peroxodisulphate is hydrolyzed to obtain hydrogen peroxide.

2HSO–4(aq) [Electrolysis] → HO3SOOSO3H(aq) [Hydrolysis] → 2HSO–4(aq)+2H+(aq)+H2O2(aq)

• Auto oxidation- In this method of production of Hydrogen Peroxide, anthraquinone is reduced to anthraquinol by dissolving in an organic solvent and passing hydrogen in the presence of pd. When anthraquinol is frothed with air, 20% solution of H2O2 is obtained and anthraquinone is generated.

Reactions of Hydrogen Peroxide

Hydrogen Peroxide acts as a oxidizing agent as well as a reducing agent in both acidic and basic medium. The reactions of Hydrogen Peroxide are:

Oxidation Reaction of H2O2

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Bleaching Reaction

Hydrogen Peroxide bleaches by oxidation and is used as a bleaching agent for silk, wool, cotton and hair

Reaction- H2O2→H2O+ (O) Nascent oxygen

Reduction Reaction

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NEET Study Notes for Water

Physical Properties of Water

• Water is a colorless and tasteless and odorless liquid in its natural state.
• The Boiling Point of water is the temperature vapor pressure of of liquid is equal to the pressure surrounding the liquid. Thus liquid changes into vapor. Boiling point of water is 100 C.
• Freezing Point of water is the temperature at which water turns to ice. This freezing point of water is 0C to 32 F.
• Heat Capacity- Due to the extensive hydrogen bonding between water molecules, the heat capacity of water is 4.2 joules per gram at 25C.
• The tendency of of water to shrink in a minimum surface area is known as surface tension of water. The surface tension of water is 72 mN at 25 C.
• Refractive Index of water describes the how fast light reaches the surface. Refractive Index of water is 1.333 at 20C.

Chemical Properties of Water

• Amphoteric Nature of water- Since water can act as an acid as well as a base, this lends to water its amphoteric nature.
• Reddox Reactions- Electropositive elements reduce water to Hydrogen molecules. Water is oxidized to O2 during the process of photosynthesis. Due to this property of water, it is useful in a redox reaction.

2H2O(l) + 2Na(s)→2NaOH (aq) + H2(g)

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Types of Hardness of water

• Temporary Hardness- Temporary Hardness of water is due to the presence of bicarbonates of calcium, magnesium or both.
• Permanent Hardness- Permanent Hardness of water is due to the presence of chlorides, sulphates of calcium and magnesium.

How to remove Temporary Hardness of water?

Temporary Hardness of water can be removed by the following methods

• Boiling- Soluble bicarbonates are converted into insoluble bicarbonates

• Clarks method- Hardness of water is removed by converting bicarbonates into carbonate by adding lime water or milk of lime.

How to remove permanent hardness?

• Adding washing soda- In this method we add, washing soda Na2CO3 to hard water.It combines with chloride salts of calcium and and magnesium present in water to form compounds. Calcium or magnesium salts are precipated as carbonates.

• Calgon's process- Calgon (known as sodium hexametaphosphate (NaPO3)6.. Hardness in water is removed by absorption of Ca++ and Mg++ ions.
• Permutit Process- Sodium Alumninium ortho silicate (permutit) is used to remove the permanent existence of water. It exchanges the sodium ions present for diavelnt ions such as Ca2+ and Mg2+

NEET Previous Year Sample MCQs for Hydrocarbons

Question: The radioactive isotope of Hydrogen is —

1. Protium
2. Deuterium
3. Tritium
4. Hydronium

Answer: Tritium

Hydrogen has three isotopes Protrium, Deuterium and Tritium. Tritium has two neutrons because its n/p value =2 .This makes tritium unstable and therefore radioactive. Tritium is produced originally when cosmic rays comes in contact with other gases and also as a byproduct of nuclear reactors.

Question: Alkali metal and cold water react vigorously resulting in the displacement of

1. Hydrogen
2. Carbon Dioxide
3. Oxygen
4. Nitrogen

Answer: Hydrogen

Alkali metals Hydrogen, Sothium, Potassium, Rubidium, Caesium, and Francium are called alkali earth metals. Alkali metals except hydrogen are found as ionic compounds in their elemental form in nature. These are very reactive and have low melting points. On reacting vigorously with water, alkali metals produce metal hydroxide, hydrogen gas and heat.

Question: Hydrogen Bomb is due to

1. Nuclear Fusion
2. Nuclear Fission
3. Both A and B
4. None of these

Answer: A mixture of deuterium oxide and tritium oxide in space surrounding ordinary hydrogen bomb is a Hydrogen Bomb. The first step is endothermic reaction, is initiated by energy obtained from explosion of atom bomb. Nuclear Fusion is a process of fusion of two lighter nuclei that produces heavier nuclei.

Question: What is the sum of neutrons and protons in the radioactive isotope of Hydrogen?

1. 3
2. 6
3. 4
4. 5

Answer: 3

Isotopes are atoms of the same element with the same atomic number and different mass number. The three main isotopes are Protrium, Deutrium and Tritium. Hydrogen has three main isotopes- Protrium, Deutrium, Tritium. The radioactive isotope of Hydrogen is tritium and its atomic number is 1.

Question: Which of the following element’s nuclei does not have a neutron?

1. Carbon
2. Oxygen
3. Nitrogen
4. Hydrogen (Protium)

Answer: Protrium

Protrium is an isotope of Hydrogen. The hydrogen atom does not have neutrons in its tiny nucleus.

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