Question

Which of the following reaction produces Hydrogen?

• A. Mg + H2O
• B. Na₂O₂ + H₂O
• C. Marshall's acid with water
• D. All of the above

Answer 1

The correct option is A

Mg + H2O

Na${}_2$O${}_2$+ 2 H${}_2$O $\to$ 2 NaOH + H${}_2$O (hydrolysis reaction)

Marshall's acid is peroxydisulphuric acid with the formula: H${}_2$S${}_2$O${}_8$

It is of the form:

It hydrolyses into Caro's acid (H${}_2$SO${}_5$) and sulphuric acid. This will be dealt with later when Oxy and oxo acids of Sulphur shall be studied.

Mg(s) + 2H${}_2$O(g) $\to$ Mg(OH)${}_2$(aq) + H${}_2$(g)

In the above reaction, Mg can be substituted with CaSr and Ba, all of which react rapidly with water (even cold). Mg reacts with hot water or steam. Be probably reacts with steam. Often it is taken to be unreactive with Steam even at very high temperatures.