NCERT Class XI Chemistry Hydrogen Solutions

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NCERT Class XI Chemistry Hydrogen Solutions

Question : 7

Total: 36

Discuss the consequences of high enthalpy of H — H bond in terms of chemical reactivity of dihydrogen.

Solution:

Dihydrogen is quite stable and dissociates into hydrogen atoms only when heated at about 2000 K.
H2(g)

2000K

→

H(g)+H(g)
Above 2000 K, the dissociation of hydrogen into atoms is only 0.081% which increases to 95.5% at 5000 K. Its bond dissociation energy is very high.
H2 → H + H ; ΔH = 435.9 kJmol–1
Due to its high bond dissociation energy it is not very reactive.

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