Chapter 9 Hydrogen Solutions
Question - 1 : - Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
Answer - 1 : -
Hydrogen has been placed at the top of the alkali metal in group, but it is not a member of the group.
Its position is not justified properly because of its electronic configuration as (1s1). It can be placed with alkali metals because it also has similar configuration (ns1) as alkali metals.
However, it can also be placed along with halogen in group 17 since just like halogen it can acquire inert gas configuration by accepting one electron.
Question - 2 : - Write the names of isotopes of hydrogen. What is the mass ratio of these isotopes?
Answer - 2 : - 
Question - 3 : - Why does hydrogen occur in a diatomic form rather than in a monoatomic form under normal conditions?
Answer - 3 : - In diatomic form, the K-shell of hydrogen is complete (1s2) and so it is quite stable.
Question - 4 : - How can the production of dihydrogen obtained from ‘Coal gasification’ be increased?
Answer - 4 : - The production of dihydrogen in coal gasification can be increased by reacting CO(y) present in syngas with steam in the presence of iron chromate catalysts.
With the removal of C02 the reaction shifts in the forward direction and thus, the production of dihydrogen will be increased.
Question - 5 : - Describe the bulk preparation of dihydrogen by electrolytic method. What is the role of an electrolyte in this process?
Answer - 5 : - In bulk, hydrogen can be produced by electrolysis of acidified water using Pt electrodes.
Electrolyte is added to increase the dissociation of water.
Question - 6 : - Complete the following reactions.
Answer - 6 : -
Question - 7 : - Discuss the consequences of high enthalpy of H-H bond, in terms of chemical reactivity of dihydrogen.
Answer - 7 : - This is due to its small atomic size and also small bond length (74 pm) of H-H bond.
Question - 8 : - What do you understand by (i) Electron-deficient (ii) Electron-precise (iii) Electron-rich compounds of hydrogen? Provide justification with suitable examples.
Answer - 8 : -
(i) Electron deficient hydrides: Compounds in whichcentral atom has incomplete octet, are called electron deficient hydrides. Forexample, BeH2, BH3 are electron deficient hydrides.
(ii) Electron precise hydrides: Thosecompounds in which exact number of electrons are present in central atom or thecentral atom contains complete octet are called precise hydrides e.g., CH4,SiH4, GeH4 etc. are precise hydrides.
(iii) Electron rich hydrides: Thosecompounds in which central atom has one or more lone pair of excess electronsare called electron rich hydrides, e.g.,NH3, H2O.
Question - 9 : - What characteristics do you expect from an electron-deficient hydride with respect to its structure and chemical reaction?
Answer - 9 : - It is expected to be a Lewis acid. They are likely to accept electrons to become stable. They can form coordinate bond with electron rich compound.
Question - 10 : - Do you expect the carbon hydride of type Cn H2n+2 to act as‘Lewis’ acid or base? Justify your answer.
Answer - 10 : -
Carbon hydrides of thetype Cn H2n+2 are electron precise hydrides. Because theyhave atom with exact number of electrons to form covalent bonds. Thus, they donot behave as Lewis acid or base. Since they have no tendency to accept or loseelectrons.