CBSE Class 11 Chemistry Hydrogen Worksheet Set A

Short Answer

Question. What is the difference between hydrogen and dihydrogen? 
Answer. Hydrogen is the lightest chemical element with the symbol h with an atomic number of 1 and atomic weight of 100794 whereas dihydrogen is the divalent radical formed from two separate hydrogen atoms or ions.

Question. What is the occurrence of dihydrogen? 
Answer. Dihydrogen is the most abundant element in the universe 70% of the total mass of the universe and is the principal element in the solar atmosphere. So, due to its light nature, it is much less abundant 0.15% by mass in the earth's atmosphere.

Question. What do you mean hydrides? 
Answer. A hydride is the anion of hydrogen, H−, or more commonly it is a compound in which one or more hydrogen centres have nucleophiles’, reducing, or basic properties. In compounds that are regarded as hydrides, the hydrogen atom is bonded to a more electropositive element or groups.

Question. Why hydrogen is considered as a simplest atomic structure? 
Answer. Hydrogen is considered to have the simplest atomic structure because it has the fewest subatomic particles of any element. It has a negative charge of -1 unit. There is only one orbital for hydrogen. For any normal atom, the number of electrons and protons is equal, meaning the electrical charge is balanced.

Question. What do you mean by the term ionic hydrides?
Answer. Ionic hydrides are compounds form between hydrogen and the most active metals, especially with the alkali and alkaline-earth metals of group one and two elements. In this group, the hydrogen acts as the hydride ion (H−). They bond with more electro positive metal atoms. 

Long Answer

Question. What are the uses of dihydrogen? 
Answer. The uses of dihydrogen are:
1. Dihydrogen is used in the synthesis of ammonia which is used in the manufacture of the nitric acid and nitrogenous fertilizers.
2. Dihydrogen is used in the manufacture id vanaspati fat by the hydrogenation of the polyunsaturated vegetable oils like soyabean, cotton seeds etc.
3. Dihydrogen is used in the manufacture of the bulk organic chemicals.
4. Dihydrogen is used for the preparation of hydrogen chloride, useful chemical.
5. Dihydrogen is used as a rocket fuel in space research.
6. Dihydrogen is used in fuel cells for generating the electrical energy.
7. Dihydrogen is used to reduce heavy metal oxides to metals.
8. Dihydrogen is used for cutting and welding purpose.

Question. Distinguish between protium and deuterium? 
Answer. 1. Protium is an isotope of hydrogen which contains one proton and one electron whereas deuterium is an isotope of hydrogen having a proton, neutron and electron.
2. Protium mass number is 1 whereas deuterium mass number is 2.
3. Protium atomic mass is 1.00794 amu whereas deuterium atomic mass is 2.014amu.
4. Protium contains one proton whereas deuterium contains a proton and a neutron.
5. Protium abundance is about 99.9% whereas deuterium abundance is about 0.002%.
6. Protium is used as a component in common compounds such as water, medicine etc. whereas deuterium is used as a component in heavy water.

Question. Explain the physical and chemical properties of the dihydrogen? 
Answer. Physical properties of dihydrogen are:
1. Dihydrogen is a colourless, odourless, tasteless combustible gas.
2. Dihydrogen is lighter than air.
3. Dihydrogen is insoluble in water.
4. Dihydrogen is neutral to litmus.
Chemical properties of dihydrogen:
1. Reaction with metals: With the transition metals such as Pd, Ni, Pt etc. dihydrogen forms the interstitial hydrides in which the small molecules of the dihydrogen takes the interstitial sites in crystal lattices of these hydrides. As a result, of which the formation of interstitial hydrides, these metals adsorb very large volume of hydrogen on their surface.
2. Reaction with non-metals: The reactivity of the halogen towards dihydrogen decreases as follows, F2 > Cl2 > Br2 > I2. As a result, F2 reacts in the dark; Cl2 in
presence of the sunlight, Br2 reacts only upon heating while reaction with I2 occurs in presence of the catalyst.
3. Reactions with the organic compounds: it reacts with many organic compounds in the presence of the catalysts to give the useful hydrogenated products of commercial importance.

Question. Explain the methods of preparation of dihydrogen? 
Answer. The two methods of preparation of dihydrogen are:
1. Laboratory preparation of dihydrogen:
a. It is usually prepared by the reaction of granulated zinc with the dilute hydrochloric acid.
b. It can also be prepared by the reaction of zinc with the aqueous alkali.
2. Commercial production of dihydrogen:
a. Electrolysis of acidified water using platinum electrodes gives hydrogen.
b. High purity dihydrogen is obtained by electrolysing warm aqueous barium hydroxide solution between nickel electrodes.
c. It is obtained as a by-product in the manufacture of the sodium hydroxide and chlorine by the electrolysis of brine solution.
d. Reaction of steam on hydrocarbons or coke at high temperatures in the presence of the catalyst yields hydrogen.
e. The production of dihydrogen can be increased by reacting with the carbon monoxide of syngas mixtures with the steam in the presence of iron chromate as a catalyst.

Question. Difference between deuterium and tritium?
Answer. 1. Deuterium is the isotope of hydrogen i.e. composed of one proton, one neutron and one electron whereas tritium is the isotope of hydrogen i.e. composed of one proton, two neutrons and one electron.
2. Deuterium mass number is 2 whereas tritium mass number is 3.
3. Deuterium atomic mass is 2.014 amu whereas tritium atomic mass is 3.016 amu.
4. Deuterium is not radioactive whereas tritium is radioactive.
5. Deuterium abundance is about 0.015% whereas tritium abundance found in trace amounts.
6. In deuterium number of neutrons is one whereas in tritium numbers of neutrons are two.