Question

Consider the following statements.

I. Atomic hydrogen is obtained by passing hydrogen through an electric arc.
II. Hydrogen gas will not reduce heated aluminium oxide.
III. Finely divided palladium absorbs large volume of hydrogen gas.

Which of the above statement(s) is(are) correct:

• A. I alone
• B. II alone
• C. I, II and III
• D. II, III
• E. None of these

Answer 1

Answer: (C)

I, II and III

(i) Atomic hydrogen is obtained by passing ordinary hydrogen through an electric arc maintained between two tungsten electrodes. The reaction is endothermic.
$\underset{\text{Molecular hydrogen}}{H_2}\underset{{200}^{0}C}{\overset{\text{electric arc}}{\to }}\underset{\text{atomic hydrogen}}{2H}\Delta H=+104.5kcal$
(ii) Hydrogen gas will not reduce oxides of strongly electropositive metals like alkali metals, alkaline earth metals, zinc and aluminium.
Hence, hydrogen gas will not reduce heated aluminium oxide.
(iii) Finely divided palladium absorbs large volume of hydrogen gas.
Palladium in the powdered state can occlude nearly 1000 times its own volume of hydrogen.
Thus, all the three statements are correct.