Hydrogen

Question 1

Ionisation Enthalpy of H

Answer 1

High;Similar to halogens:
F>H>Li

Question 2

Reactivity of H

Answer 2

Low as compared to halogens

Question 3

Abundance of H

Answer 3

H2 is the most abundant in the universe but due to its low mass it is much less abundant in the earths atmosphere

Question 4

Terestial hydrogen contains deuterium as

Answer 4

HD

Question 5

Radioactivity of Tritium

Answer 5

it emits low energy beta- particles and has a half life of 12.33 yrs

Question 6

Highly pure H2 is produced by

Answer 6

Electrolysis of aq Ba(OH)2 solution with Ni electrodes

Question 7

H2 is produced by

Answer 7

-Electrolysis of brine solution
-reaction of steam on hydrocarbons at high temperature in presence of Ni.
-77% of H2 is produced from petrochemicals

Question 8

Water gas shift reaction

Answer 8

CO+H2O=CO2+H2
CO2 is removed by scrubbing with sodium arsenite

Question 9

Dissociation of H2

Answer 9

0.081% at 2000K and 95.5% at 5000K

Question 10

Reactivity with halogens

Answer 10

Reacts to form HX. Reaction with F takes place even in dark but catalyst is required for I.

Question 11

Reaction with N2

Answer 11

H2 and N2 react in presence of Fe catalyst at 673K to form NH3

Question 12

Reaction with metal ions

Answer 12

It reduces certain metals less reactive than Fe

Question 13

Reaction with organic compounds

Answer 13

-Hydrogenation
-Hydroformylation (reaction with unsaturated compounds with CO to form CHO; on further reaction CHO is reduced to CH2OH)

Question 14

Uses of H2

Answer 14

-Largest use is production of NH3
-manufacture of methanol(syn gas in presence of Co)
-metal hydrites
-atomic and oxy-hydrogen torches
-as rocket fuel

Question 15

Hydrides types

Answer 15

-ionic or saline or salt-like
-covalent
-metallic or non-stoichiometric

Question 16

Ionic Hydrides

Answer 16

-S-block elements(except lighter elements like LiH, BeH2, MgH2)
-BeH2 and MgH2 are polymeric
-crystalline, non-conducting in solid state
-react violently with H2O to give H2
-LiH is unreactive and thus used in synthesis of other hydrides

Question 17

Covalent Hydrides

Answer 17

Electron deficient-group 13
Electron precise- group 14
Electron rich- groups 15,16,17

Question 18

Metallic Hydrides

Answer 18

-D-block elements
-Groups 7,8,9 don’t form hydride
-from group 16 only Cr does
-conduct heat and electricity but not as efficiently as metals
-hydrides have different lattice(except Ni,Pd,Ce,Ac)

Question 19

Uses of metallic hydrides

Answer 19

-used in catalytic hydrogenation
-used as storage media of H2

Question 20

Ice

Answer 20

Ice has a highly ordered three dimensional
hydrogen bonded structure. X-rays shows that each oxygen atom is
surrounded tetrahedrally by four other oxygen

Question 21

Crystallisation of ice

Answer 21

At atmospheric pressure ice crystallises in the
hexagonal form, but at very low temperatures
it condenses to cubic form

Question 22

Redox reactions of H2O

Answer 22

-Reduced by electropositive metals
-Oxidised by O2 during photosynthesis and also by F2

Question 23

Hydrates of salts

Answer 23

Coordinated water-[Cr(H2O)6]3+
Interstitial water-BaCl2.2H2O
Hydrogen bonded water-[Cu(H2O)4]2-(SO4)2-.H2O

Question 24

Temporary hardness

Answer 24

-Presence of hydrogencarbonates
-can be removed by boiling or with Ca(OH)2 (Clark’s Method)

Question 25

Permanent Hardness

Answer 25

-Presence of (SO4)2- and Cl- -can be removed with washing soda; with calgon Na6P6O18; with zeolite NaSiAlO4; with synthetic ion exchangers