Question

Which of the following statement about hydrogen is incorrect ?

• A. Hydrogen never acts as cation in ionic salts
• B. Hydronium ion, ${H_3O^+}$ exists freely in solution
• C. Dihydrogen does not act as a reducing agent
• D. Hydrogen has three isotopes of which tritium is the most common

Answer 1

The Correct Option is D

Hydrogen and its Reactions 

Hydrogen can exist as a hydride \({(H^{-})}\) in ionic salts.

The most abundant form of hydrogen is protium, which consists of a single proton and electron.

Dihydrogen (\({H_2(g)}\)) has the ability to reduce some metal ions in aqueous solutions and oxides of metals that are less active than iron into the corresponding metals. This reduction process can be shown as:

\({H_2(g) + Pd^{2+} (aq) \rightarrow Pd(s) + 2 H^{+} (aq)}\)

This reaction shows how dihydrogen reduces palladium ions (\({Pd^{2+}}\)) into solid palladium metal (\({Pd(s)}\)), with the formation of hydrogen ions (\({H^{+}}\)) in the process.

Another example of reduction is when dihydrogen reacts with metal oxides:

\({yH_2(g) + M_x O_y(s) \rightarrow xM(s) + yH_2O(\ell)}\)

In this reaction, dihydrogen reduces the metal oxide (\({M_x O_y}\)) to produce the metal (\({M(s)}\)) and water (\({H_2O(\ell)}\)).