Hydrogen

Preparation and Properties of Dihydrogen

Although Hydrogen is abundantly present in our atmosphere, it is not found in the free state. And there are various uses and applications of Hydrogen for domestic and industrial purposes. So let us learn about the properties and preparation of Dihydrogen.

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Preparation of Dihydrogen

Laboratory Preparation of Dihydrogen

  • Reacting Zinc with Acid

One common way to prepare dihydrogen gas in the lab is by reacting Zinc with a diluted acid. It results in Zinc forming Zinc Sulphate (or zinc chloride) and releasing hydrogen in a gas form

Zn + H2SO4 → ZnSO4 + H2

Zn +HCl → ZnCl2 + H2

  • Reacting Zinc with Alkaline

Zinc can also react with an aqueous alkali such as Sodium Hydroxide, The sodium and zinc will combine and give us dihydrogen as another product. The reaction is as follows

Zn + 2NaOH → Na2ZnO2 + H2

Commercial Preparation of Dihydrogen

The commercial preparation of hydrogen is a huge industry because there is a huge demand for hydrogen in the production of fertilizers and oil-refining process.

  • Electrolysis of Water

The method helps in the production of a very pure form of hydrogen from water. Electricity passes through the water breaking up the water molecule. The hydrogen collects at the cathode while oxygen collects at the anode.

  • Lane’s Process

Here Water Gas (a mixture of carbon monoxide and hydrogen) and steam are alternatively passed over iron at very high temperatures of up to 800 C. The iron is first oxidized releasing hydrogen and has to replaced with fresh metal. Then the iron reduces with water gas back to a metal. The reactions are as follows

3Fe + 4H2O → Fe3O4  + 4H2

Fe3O4 + 4CO → 3Fe + 4CO2

Net reaction is

CO + H2O → CO2 + H2

  • From Natural Gas

This remains the cheapest way to produce hydrogen on a commercial scale. The gas is heated to high temperatures (up to 1100 C) with steam and a Nickel catalyst. This results in the methane molecules breaking into Carbon Monoxide and Hydrogen.

CH4 + H2O→ CO + 3H2

Properties of Dihydrogen

Physical Properties of Dihydrogen

  • At room temperature, this diatomic molecule of hydrogen is found in a gaseous state
  • It is an absolutely colorless, odorless and tasteless gas which makes it very hard to detect
  • It is the lightest element of our periodic table. Has the molecular weight f 1.00794
  • It also has the lowest density of all elements
  • It is highly combustible or inflammable. On combustion it produces water. Also, it burns with a blue flame.
  • It liquefies at very low temperatures of nearly -250 C

Chemical Properties of Dihydrogen

  • Hydrogen is represented by its symbol ‘H’. However, in nature, it occurs in its diatomic form as ‘H2‘ known as Dihydrogen
  • Hydrogen has no effect on litmus paper, i.e. it is neutral (neither acidic nor alkaline)
  • Dihydrogen is a non-metal
  • It is fairly non-reactive in nature. Since dihydrogen is a stable molecule it is not very reactive
  • Dihydrogen has high enthalpy due to its stable H-H bond
  • It is an oxidizing agent when reacting with metals. It forms metal hydrides.
  • Reacts with unsaturated Hydrocarbon (for example ethene) to form saturated hydrocarbons
  • Reduces metal oxides of metals less reactive than iron (iron included)

Solved Question for You

Question: When hydrogen burns in oxygen, water is formed and when water is electrolyzed then hydrogen and oxygen are produced. What type of a reaction takes place (i) in the first case, and (ii) in the second case

  1. In both the cases, i.e. (i) and (ii), a combination reaction takes place.
  2. In the first case, a combination reaction takes place and in the second case, a decomposition reaction takes place.
  3. The first case, a combination reaction takes place and in the second case, a displacement reaction takes place.
  4. Or in the first case, a displacement reaction takes place and in the second case, a decomposition reaction takes place.

Ans: The correct answer is option “B”. In the first case, the two elements, hydrogen, and oxygen combine to form a single compound hence it is a combination reaction. In the second case, a decomposition reaction takes place as a single compound, i.e. water, splits up to form two simple substances-hydrogen and oxygen. This decomposition reaction takes place by the action of electricity.

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ijazkhan

melting point of cacl2 as compared to cal2

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